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					      United States
Department of Agriculture



       Keys to
   Soil Taxonomy
             Eleventh Edition, 2010
Keys to Soil Taxonomy
By Soil Survey Staff




United States Department of Agriculture
Natural Resources Conservation Service

Eleventh Edition, 2010
ii	




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          Cover: Profile of a Lamellic Quartzipsamment. Because of coatings of iron oxide, the part of the profile
      directly below the surface horizon is reddish. Lamellae of loamy sand, mostly less than 0.5 centimeter thick,
      are common in the lower part of the profile. The scale is in 15-centimeter increments. Photo by John Kelley,
      Soil Scientist (retired), Raleigh, North Carolina.
                                                                                                                                                  iii




                                                                                                                           Table of Contents

Foreword .....................................................................................................................................v
Chapter 1: The Soils That We Classify ...................................................................................1
Chapter 2: Differentiae for Mineral Soils and Organic Soils ..................................................3
Chapter 3: Horizons and Characteristics Diagnostic for the Higher Categories .....................5
Chapter 4: Identification of the Taxonomic Class of a Soil ..................................................31
Chapter 5: Alfisols ................................................................................................................35
Chapter 6: Andisols ...............................................................................................................77
Chapter 7: Aridisols ..............................................................................................................97
Chapter 8: Entisols ..............................................................................................................123
Chapter 9: Gelisols ..............................................................................................................145
Chapter 10: Histosols ............................................................................................................155
Chapter 11: Inceptisols..........................................................................................................161
Chapter 12: Mollisols ............................................................................................................197
Chapter 13: Oxisols ...............................................................................................................241
Chapter 14: Spodosols ..........................................................................................................257
Chapter 15: Ultisols ..............................................................................................................267
Chapter 16: Vertisols .............................................................................................................287
Chapter 17: Family and Series Differentiae and Names .......................................................299
Chapter 18: Designations for Horizons and Layers ..............................................................315
Appendix ................................................................................................................................323
Index ......................................................................................................................................331
                                                                                                           v




                                                                                                    Foreword

    The publication Keys to Soil Taxonomy serves two purposes. It provides the taxonomic
keys necessary for the classification of soils in a form that can be used easily in the field. It
also acquaints users of the taxonomic system with recent changes in the system. The eleventh
edition of the Keys to Soil Taxonomy incorporates all changes approved since the publication
of the second edition of Soil Taxonomy: A Basic System of Soil Classification for Making and
Interpreting Soil Surveys (1999). One of the most significant changes in the eleventh edition
is the addition of the suborders Wassents and Wassists for subaqueous Entisols and Histosols.
We plan to continue issuing updated editions of the Keys to Soil Taxonomy as changes warrant
new editions.
    Since it was first published 35 years ago, Soil Taxonomy: A Basic System of Soil
Classification for Making and Interpreting Soil Surveys has been used to support soil survey
efforts in many countries around the world. It has been translated into several languages.
Soil scientists from many nations have contributed significantly to the development of the
taxonomic system. The authors encourage the continued use of soil taxonomy internationally
and look forward to future collaborations with the international soil science community so we
can continue to make improvements. Through continued communication and collaboration,
we hope that our efforts will eventually result in a truly universal soil classification system.
    The authors of the Keys to Soil Taxonomy are identified as the “Soil Survey Staff.” This
term is meant to include all of the soil classifiers in the National Cooperative Soil Survey
program and in the international community who have made significant contributions to the
improvement of the taxonomic system.


Micheal L. Golden
Director, Soil Survey Division
Natural Resources Conservation Service
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CHAPTER 1

                                                                                     The Soils That We Classify

    The word “soil,” like many common words, has several              is arbitrarily set at 200 cm. In soils where either biological
meanings. In its traditional meaning, soil is the natural medium      activity or current pedogenic processes extend to depths greater
for the growth of land plants, whether or not it has discernible      than 200 cm, the lower limit of the soil for classification
soil horizons. This meaning is still the common understanding         purposes is still 200 cm. In some instances the more weakly
of the word, and the greatest interest in soil is centered on this    cemented bedrocks (paralithic materials, defined later) have
meaning. People consider soil important because it supports           been described and used to differentiate soil series (series
plants that supply food, fibers, drugs, and other wants of            control section, defined later), even though the paralithic
humans and because it filters water and recycles wastes. Soil         materials below a paralithic contact are not considered soil in
covers the earth’s surface as a continuum, except on bare rock,       the true sense. In areas where soil has thin cemented horizons
in areas of perpetual frost, in deep water, or on the barren ice of   that are impermeable to roots, the soil extends as deep as the
glaciers. In this sense, soil has a thickness that is determined by   deepest cemented horizon, but not below 200 cm. For certain
the rooting depth of plants.                                          management goals, layers deeper than the lower boundary of
    Soil in this text is a natural body comprised of solids           the soil that is classified (200 cm) must also be described if
(minerals and organic matter), liquid, and gases that occurs          they affect the content and movement of water and air or other
on the land surface, occupies space, and is characterized by          interpretative concerns.
one or both of the following: horizons, or layers, that are               In the humid tropics, earthy materials may extend to a depth
distinguishable from the initial material as a result of additions,   of many meters with no obvious changes below the upper 1 or
losses, transfers, and transformations of energy and matter or        2 m, except for an occasional stone line. In many wet soils,
the ability to support rooted plants in a natural environment.        gleyed soil material may begin a few centimeters below the
This definition is expanded from the 1975 version of Soil             surface and, in some areas, continue down for several meters
Taxonomy to include soils in areas of Antarctica where                apparently unchanged with increasing depth. The latter
pedogenesis occurs but where the climate is too harsh to support      condition can arise through the gradual filling of a wet basin
the higher plant forms.                                               in which the A horizon is gradually added to the surface and
    The upper limit of soil is the boundary between soil and          becomes gleyed beneath. Finally, the A horizon rests on a thick
air, shallow water, live plants, or plant materials that have not     mass of gleyed material that may be relatively uniform. In both
begun to decompose. Areas are not considered to have soil if          of these situations, there is no alternative but to set the lower
the surface is permanently covered by water too deep (typically       limit of soil at the arbitrary limit of 200 cm.
more than about 2.5 m) for the growth of rooted plants. The               Soil, as defined in this text, does not need to have discernible
horizontal boundaries of soil are areas where the soil grades         horizons, although the presence or absence of horizons and their
to deep water, barren areas, rock, or ice. In some places the         nature are of extreme importance in soil classification. Plants
separation between soil and nonsoil is so gradual that clear          can be grown under glass in pots filled with earthy materials,
distinctions cannot be made.                                          such as peat or sand, or even in water. Under proper conditions
    The lower boundary that separates soil from the nonsoil           all these media are productive for plants, but they are nonsoil
underneath is most difficult to define. Soil consists of              here in the sense that they cannot be classified in the same
the horizons near the earth’s surface that, in contrast to            system that is used for the soils of a survey area, county, or
the underlying parent material, have been altered by the              even nation. Plants even grow on trees, but trees are regarded as
interactions of climate, relief, and living organisms over time.      nonsoil.
Commonly, soil grades at its lower boundary to hard rock or               Soil has many properties that fluctuate with the seasons. It
to earthy materials virtually devoid of animals, roots, or other      may be alternately cold and warm or dry and moist. Biological
marks of biological activity. The lowest depth of biological          activity is slowed or stopped if the soil becomes too cold or too
activity, however, is difficult to discern and is often gradual.      dry. The soil receives flushes of organic matter when leaves fall
For purposes of classification, the lower boundary of soil            or grasses die. Soil is not static. The pH, soluble salts, amount
2



of organic matter and carbon-nitrogen ratio, numbers of micro-    establish a phase of the mantled soil or even another soil series
organisms, soil fauna, temperature, and moisture all change       if the mantle affects the use of the soil.
with the seasons as well as with more extended periods of time.       Any horizons or layers underlying a plaggen epipedon are
Soil must be viewed from both the short-term and long-term        considered to be buried.
perspective.                                                          A surface mantle of new material, as defined here, is largely
                                                                  unaltered, at least in the lower part. It may have a diagnostic
                                                                  surface horizon (epipedon) and/or a cambic horizon, but it
Buried Soils
                                                                  has no other diagnostic subsurface horizons, all defined later.
    A buried soil is covered with a surface mantle of new soil    However, there remains a layer 7.5 cm or more thick that fails
material that either is 50 cm or more thick or is 30 to 50 cm     the requirements for all diagnostic horizons, as defined later,
thick and has a thickness that equals at least half the total     overlying a horizon sequence that can be clearly identified as
thickness of the named diagnostic horizons that are preserved     the solum of a buried soil in at least half of each pedon. The
in the buried soil. A surface mantle of new material that does    recognition of a surface mantle should not be based only on
not have the required thickness for buried soils can be used to   studies of associated soils.
                                                                                                                                                                3




                                                                                                                                                                     D
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CHAPTER 2                                                                                                                                                            F




                                                                  Differentiae for Mineral Soils1 and Organic Soils

    Soil taxonomy differentiates between mineral soils and                                    include what has been called litter or an O horizon. Material
organic soils. To do this, first, it is necessary to distinguish                              that has more organic carbon than in item 2 has been called
mineral soil material from organic soil material. Second, it                                  peat or muck. Not all organic soil material accumulates in or
is necessary to define the minimum part of a soil that should                                 under water. Leaf litter may rest on a lithic contact and support
be mineral if a soil is to be classified as a mineral soil and                                forest vegetation. The soil in this situation is organic only in
the minimum part that should be organic if the soil is to be                                  the sense that the mineral fraction is appreciably less than half
classified as an organic soil.                                                                the weight and is only a small percentage of the volume of the
    Nearly all soils contain more than traces of both mineral                                 soil.
and organic components in some horizons, but most soils
are dominantly one or the other. The horizons that are less                                   Distinction Between Mineral Soils and Organic
than about 20 to 35 percent organic matter, by weight, have
                                                                                                 Soils
properties that are more nearly those of mineral than of organic
soils. Even with this separation, the volume of organic matter at                                Most soils are dominantly mineral material, but many
the upper limit exceeds that of the mineral material in the fine-                             mineral soils have horizons of organic material. For simplicity
earth fraction.                                                                               in writing definitions of taxa, a distinction between what is
                                                                                              meant by a mineral soil and an organic soil is useful. To apply
                                                                                              the definitions of many taxa, one must first decide whether the
Mineral Soil Material                                                                         soil is mineral or organic. An exception is the Andisols (defined
   Mineral soil material (less than 2.0 mm in diameter) either:                               later). These generally are considered to consist of mineral soils,
                                                                                              but some may be organic if they meet other criteria for Andisols.
1. Is saturated with water for less than 30 days (cumulative)                                 Those that exceed the organic carbon limit defined for mineral
per year in normal years and contains less than 20 percent (by                                soils have a colloidal fraction dominated by short-range-
weight) organic carbon; or                                                                    order minerals or aluminum-humus complexes. The mineral
2. Is saturated with water for 30 days or more (cumulative) in                                fraction in these soils is believed to give more control to the
normal years (or is artificially drained) and, excluding live roots,                          soil properties than the organic fraction. Therefore, the soils are
has an organic carbon content (by weight) of:                                                 included with the Andisols rather than the organic soils defined
                                                                                              later as Histosols and Histels.
   a. Less than 18 percent if the mineral fraction contains 60                                   If a soil has both organic and mineral horizons, the relative
   percent or more clay; or                                                                   thickness of the organic and mineral soil materials must be
   b. Less than 12 percent if the mineral fraction contains no                                considered. At some point one must decide that the mineral
   clay; or                                                                                   horizons are more important. This point is arbitrary and depends
                                                                                              in part on the nature of the materials. A thick layer of Sphagnum
   c. Less than 12 + (clay percentage multiplied by 0.1)                                      has a very low bulk density and contains less organic matter
   percent if the mineral fraction contains less than 60 percent                              than a thinner layer of well-decomposed muck. It is much
   clay.                                                                                      easier to measure the thickness of layers in the field than it is to
                                                                                              determine tons of organic matter per hectare. The definition of a
Organic Soil Material                                                                         mineral soil, therefore, is based on the thickness of the horizons,
                                                                                              or layers, but the limits of thickness must vary with the kinds of
   Soil material that contains more than the amounts of organic                               materials. The definition that follows is intended to classify as
carbon described above for mineral soil material is considered                                mineral soils those that have both thick mineral soil layers and
organic soil material.                                                                        no more organic material than the amount permitted in the histic
   In the definition of mineral soil material above, material                                 epipedon, which is defined in chapter 3.
that has more organic carbon than in item 1 is intended to                                       In the determination of whether a soil is organic or mineral,
                                                                                              the thickness of horizons is measured from the surface of
   1
       Mineral soils include all soils except the suborder Histels and the order Histosols.   the soil whether that is the surface of a mineral or an organic
4



horizon, unless the soil is buried as defined in chapter 1.                                          a.    Permafrost within 100 cm of the soil surface; or
Thus, any O horizon at the surface is considered an organic
horizon if it meets the requirements of organic soil material                                        b. Gelic materials within 100 cm of the soil surface and
as defined later, and its thickness is added to that of any other                                    permafrost within 200 cm of the soil surface.
organic horizons to determine the total thickness of organic
soil materials. Plant materials at the soil surface must be at                                  Definition of Organic Soils
least slightly decomposed if they are to be considered part of                                       Organic soils have organic soil materials that:
an O horizon. Undecomposed plant litter is excluded from the
concept of O horizons.                                                                          1. Do not have andic soil properties in 60 percent or more
                                                                                                of the thickness between the soil surface and either a depth
Definition of Mineral Soils                                                                     of 60 cm or a densic, lithic, or paralithic contact or duripan if
                                                                                                shallower; and
    Mineral soils are soils that have either:
                                                                                                2.    Meet one or more of the following:
1. Mineral soil materials that meet one or more of the
following:                                                                                           a. Overlie cindery, fragmental, or pumiceous materials
                                                                                                     and/or fill their interstices2 and directly below these materials
    a. Overlie cindery, fragmental, or pumiceous materials                                           have a densic, lithic, or paralithic contact; or
    and/or have voids2 that are filled with 10 percent or less
    organic materials and directly below these materials have                                        b. When added with the underlying cindery, fragmental, or
    either a densic, lithic, or paralithic contact; or                                               pumiceous materials, total 40 cm or more between the soil
                                                                                                     surface and a depth of 50 cm; or
    b. When added with underlying cindery, fragmental, or
    pumiceous materials, total more than 10 cm between the soil                                      c. Constitute two-thirds or more of the total thickness of
    surface and a depth of 50 cm; or                                                                 the soil to a densic, lithic, or paralithic contact and have
                                                                                                     no mineral horizons or have mineral horizons with a total
    c. Constitute more than one-third of the total thickness of                                      thickness of 10 cm or less; or
    the soil to a densic, lithic, or paralithic contact or have a total
    thickness of more than 10 cm; or                                                                 d. Are saturated with water for 30 days or more per year
                                                                                                     in normal years (or are artificially drained), have an upper
    d. If they are saturated with water for 30 days or more per                                      boundary within 40 cm of the soil surface, and have a total
    year in normal years (or are artificially drained) and have                                      thickness of either:
    organic materials with an upper boundary within 40 cm of
    the soil surface, have a total thickness of either:                                                   (1) 60 cm or more if three-fourths or more of their
                                                                                                          volume consists of moss fibers or if their bulk density,
        (1) Less than 60 cm if three-fourths or more of their                                             moist, is less than 0.1 g/cm3; or
        volume consists of moss fibers or if their bulk density,
        moist, is less than 0.1 g/cm3; or                                                                 (2) 40 cm or more if they consist either of sapric or
                                                                                                          hemic materials, or of fibric materials with less than three-
        (2) Less than 40 cm if they consist either of sapric or                                           fourths (by volume) moss fibers and a bulk density, moist,
        hemic materials, or of fibric materials with less than three-                                     of 0.1 g/cm3 or more; or
        fourths (by volume) moss fibers and a bulk density, moist,
        of 0.1 g/cm3 or more; or                                                                     e. Are 80 percent or more, by volume, from the soil surface
                                                                                                     to a depth of 50 cm or to a glacic layer or a densic, lithic, or
2. More than 20 percent, by volume, mineral soil materials                                           paralithic contact, whichever is shallowest.
from the soil surface to a depth of 50 cm or to a glacic layer or a
densic, lithic, or paralithic contact, whichever is shallowest; and                                It is a general rule that a soil is classified as an organic soil
                                                                                                (Histosol or Histel) if more than half of the upper 80 cm (32 in)
                                                                                                of the soil is organic or if organic soil material of any thickness
     2
       Materials that meet the definition of the cindery, fragmental, or pumiceous substitute   rests on rock or on fragmental material having interstices filled
for particle-size class but have more than 10 percent, by volume, voids that are filled with    with organic materials.
organic soil materials are considered to be organic soil materials.
                                                                                                                                           5




CHAPTER 3
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                                                                                                                                                I
           Horizons and Characteristics Diagnostic for the Higher Categories                                                                    A




   This chapter defines the horizons and characteristics              indicate buried horizons, such as those in Thapto-Histic
of both mineral and organic soils. It is divided into three           subgroups. A soil with a mantle thick enough to have a buried
parts—horizons and characteristics diagnostic for mineral soils,      soil has no epipedon if the soil has rock structure to the surface
characteristics diagnostic for organic soils, and horizons and        or has an Ap horizon less than 25 cm thick that is underlain
characteristics diagnostic for both mineral and organic soils.        by soil material with rock structure. The melanic epipedon
   The horizons and characteristics defined below are not in          (defined below) is unique among epipedons. It commonly
a key format. The “required characteristics” for horizons or          forms in deposits of tephra and can receive fresh deposits of
features, however, are arranged as a key. Some diagnostic             volcanic ash. Therefore, this horizon is permitted to have layers
horizons are mutually exclusive, and some are not. An umbric          within and above the epipedon that are not part of the melanic
epipedon, for example, could not also be a mollic epipedon. A         epipedon.
kandic horizon with clay films, however, could also meet the             A recent alluvial or eolian deposit that retains fine
definition of an argillic horizon.                                    stratifications (5 mm or less thick) or an Ap horizon directly
                                                                      underlain by such stratified material is not included in the
                                                                      concept of the epipedon because time has not been sufficient
Horizons and Characteristics                                          for soil-forming processes to erase these transient marks of
  Diagnostic for Mineral Soils                                        deposition and for diagnostic and accessory properties to
                                                                      develop.
   The criteria for some of the following horizons and
                                                                         An epipedon is not the same as an A horizon. It may include
characteristics, such as histic and folistic epipedons, can be
                                                                      part or all of an illuvial B horizon if the darkening by organic
met in organic soils. They are diagnostic, however, only for the
                                                                      matter extends from the soil surface into or through the B
mineral soils.
                                                                      horizon.

Diagnostic Surface Horizons:                                          Anthropic Epipedon
   The Epipedon                                                       Required Characteristics
    The epipedon (Gr. epi, over, upon, and pedon, soil) is a
                                                                         The anthropic epipedon consists of mineral soil material that
horizon that forms at or near the surface and in which most of
                                                                      shows some evidence of disturbance by human activity. After
the rock structure has been destroyed. It is darkened by organic
                                                                      mixing of the upper 18 cm of the mineral soil, or of the whole
matter or shows evidence of eluviation, or both. Rock structure
                                                                      mineral soil if its depth to a densic, lithic, or paralithic contact, a
as used here and in other places in this taxonomy includes fine
                                                                      petrocalcic horizon, or a duripan (all defined below) is less than
stratification (5 mm or less thick) in unconsolidated sediments
                                                                      18 cm, the anthropic epipedon has the following properties:
(eolian, alluvial, lacustrine, or marine) and saprolite derived
from consolidated rocks in which the unweathered minerals             1. When dry, either or both:
and pseudomorphs of weathered minerals retain their relative
                                                                           a. Structural units with a diameter of 30 cm or less or
positions to each other.
                                                                           secondary structure with a diameter of 30 cm or less; or
    Any horizon may be at the surface of a truncated soil. The
following section, however, is concerned with eight diagnostic             b. A moderately hard or softer rupture-resistance class; and
horizons that have formed at or near the soil surface. These
                                                                      2. Rock structure, including fine stratifications (5 mm or less
horizons can be covered by a surface mantle of new soil
                                                                      thick), in less than one-half of the volume of all parts; and
material. If the surface mantle has rock structure, the top of the
epipedon is considered the soil surface unless the mantle meets       3.    One of the following:
the definition of buried soils in chapter 1. If the soil includes a
                                                                           a.    Both of the following:
buried soil, the epipedon, if any, is at the soil surface and the
epipedon of the buried soil is considered a buried epipedon and                 (1) Dominant colors with a value of 3 or less, moist, and
is not considered in selecting taxa unless the keys specifically                of 5 or less, dry; and
6                                                                                                                      Keys to Soil Taxonomy



          (2)     Dominant colors with chroma of 3 or less, moist; or          a. Has a phosphate content of 1,500 or more milligrams per
                                                                               kilogram by citric-acid extraction; and
     b. A fine-earth fraction that has a calcium carbonate
     equivalent of 15 to 40 percent and colors with value and                       (1) The phosphorus content decreases regularly with
     chroma of 3 or less, moist; or                                                 increasing depth below the epipedon; and
     c. A fine-earth fraction that has a calcium carbonate                          (2)   Phosphorus is not in the form of nodules; or
     equivalent of 40 percent or more and a color value, moist, of
                                                                               b. All parts of the epipedon are moist for less than 90 days
     5 or less; and
                                                                               (cumulative) in normal years during times when the soil
4. An organic-carbon content of:                                               temperature at a depth of 50 cm is 5 oC or higher, if the soil
                                                                               is not irrigated; and
     a. 2.5 percent or more if the epipedon has a color value,
     moist, of 4 or 5; or                                                 7. The n value (defined below) is less than 0.7.
     b. 0.6 percent more (absolute) than that of the C horizon (if
     one occurs) if the mollic epipedon has a color value less than       Folistic Epipedon
     1 unit lower or chroma less than 2 units lower (both moist           Required Characteristics
     and dry) than the C horizon; or
                                                                             The folistic epipedon is defined as a layer (one or more
     c. 0.6 percent or more and the epipedon does not meet the            horizons) that is saturated for less than 30 days (cumulative) in
     qualifications in 4-a or 4-b above; and                              normal years (and is not artificially drained) and either:
5. The minimum thickness of the epipedon is as follows:                   1.    Consists of organic soil material that:
     a.    25 cm if:                                                           a. Is 20 cm or more thick and either contains 75 percent
                                                                               or more (by volume) Sphagnum fibers or has a bulk density,
          (1) The texture class of the epipedon is loamy fine sand
                                                                               moist, of less than 0.1; or
          or coarser throughout; or
                                                                               b.    Is 15 cm or more thick; or
          (2) There are no underlying diagnostic horizons (defined
          below), and the organic-carbon content of the underlying        2. Is an Ap horizon that, when mixed to a depth of 25 cm, has
          materials decreases irregularly with increasing depth; or       an organic-carbon content (by weight) of:
          (3) Any of the following, if present, are 75 cm or more              a. 16 percent or more if the mineral fraction contains 60
          below the mineral soil surface:                                      percent or more clay; or
                (a) The upper boundary of the shallowest of any                b. 8 percent or more if the mineral fraction contains no
                identifiable secondary carbonates or a calcic horizon,         clay; or
                petrocalcic horizon, duripan, or fragipan (defined
                                                                               c. 8 + (clay percentage divided by 7.5) percent or more if
                below); and/or
                                                                               the mineral fraction contains less than 60 percent clay.
                (b) The lower boundary of the deepest of an argillic,
                                                                             Most folistic epipedons consist of organic soil material
                cambic, natric, oxic, or spodic horizon; or
                                                                          (defined in chapter 2). Item 2 provides for a folistic epipedon
     b. 10 cm if the epipedon has a texture class finer than              that is an Ap horizon consisting of mineral soil material.
     loamy fine sand (when mixed) and it is directly above a
     densic, lithic, or paralithic contact, a petrocalcic horizon, or a   Histic Epipedon
     duripan; or
                                                                          Required Characteristics
     c. 18 to 25 cm and the thickness is one-third or more of the
                                                                             The histic epipedon is a layer (one or more horizons) that is
     total thickness between the mineral soil surface and:
                                                                          characterized by saturation (for 30 days or more, cumulative)
                (1) The upper boundary of the shallowest of any           and reduction for some time during normal years (or is
                identifiable secondary carbonates or a calcic horizon,    artificially drained) and either:
                petrocalcic horizon, duripan, or fragipan; and/or
                                                                          1.    Consists of organic soil material that:
                (2) The lower boundary of the deepest of an argillic,
                                                                               a. Is 20 to 60 cm thick and either contains 75 percent or
                cambic, natric, oxic, or spodic horizon; or
                                                                               more (by volume) Sphagnum fibers or has a bulk density,
     d.    18 cm if none of the above conditions apply.                        moist, of less than 0.1; or
6.    One or both of the following:                                            b.    Is 20 to 40 cm thick; or
Horizons and Characteristics Diagnostic for the Higher Categories                                                                           7



2. Is an Ap horizon that, when mixed to a depth of 25 cm, has                (1) Dominant colors with a value of 3 or less, moist, and
an organic-carbon content (by weight) of:                                    of 5 or less, dry; and
     a. 16 percent or more if the mineral fraction contains 60               (2)     Dominant colors with chroma of 3 or less, moist; or
     percent or more clay; or
                                                                        b. A fine-earth fraction that has a calcium carbonate                   D
                                                                                                                                                I
     b. 8 percent or more if the mineral fraction contains no           equivalent of 15 to 40 percent and colors with a value and              A
     clay; or                                                           chroma of 3 or less, moist; or
     c. 8 + (clay percentage divided by 7.5) percent or more if         c. A fine-earth fraction that has a calcium carbonate
     the mineral fraction contains less than 60 percent clay.           equivalent of 40 percent or more and a color value, moist, of
                                                                        5 or less; and
    Most histic epipedons consist of organic soil material
(defined in chapter 2). Item 2 provides for a histic epipedon that    4. A base saturation (by NH4OAc) of 50 percent or more
is an Ap horizon consisting of mineral soil material. A histic        throughout; and
epipedon consisting of mineral soil material can also be part of
                                                                      5. An organic-carbon content of:
a mollic or umbric epipedon.
                                                                        a. 2.5 percent or more if the epipedon has a color value,
Melanic Epipedon                                                        moist, of 4 or 5; or

Required Characteristics                                                b. 0.6 percent (absolute) more than that of the C horizon (if
                                                                        one occurs) if the mollic epipedon has a color value less than
     The melanic epipedon has both of the following:                    1 unit lower or chroma less than 2 units lower (both moist
1. An upper boundary at, or within 30 cm of, either the                 and dry) than the C horizon; or
mineral soil surface or the upper boundary of an organic                c. 0.6 percent or more and the epipedon does not meet the
layer with andic soil properties (defined below), whichever is          qualifications in 5-a or 5-b above; and
shallower; and
                                                                      6. The minimum thickness of the epipedon is as follows:
2. In layers with a cumulative thickness of 30 cm or more
within a total thickness of 40 cm, all of the following:                a.    25 cm if:

     a. Andic soil properties throughout; and                                (1) The texture class of the epipedon is loamy fine sand
                                                                             or coarser throughout; or
     b. A color value, moist, and chroma of 2 or less throughout
     and a melanic index of 1.70 or less throughout; and                     (2) There are no underlying diagnostic horizons
                                                                             (defined below) and the organic-carbon content of the
     c. 6 percent or more organic carbon as a weighted average               underlying materials decreases irregularly with increasing
     and 4 percent or more organic carbon in all layers.                     depth; or
                                                                             (3) Any of the following, if present, are 75 cm or more
Mollic Epipedon                                                              below the mineral soil surface:
Required Characteristics
                                                                                   (a) The upper boundary of the shallowest of any
   The mollic epipedon consists of mineral soil materials and,                     identifiable secondary carbonates or a calcic horizon,
after mixing of the upper 18 cm of the mineral soil or of the                      petrocalcic horizon, duripan, or fragipan (defined
whole mineral soil if its depth to a densic, lithic, or paralithic                 below); and/or
contact, a petrocalcic horizon, or a duripan (all defined below) is
                                                                                   (b) The lower boundary of the deepest of an argillic,
less than 18 cm, has the following properties:
                                                                                   cambic, natric, oxic, or spodic horizon; or
1. When dry, either or both:
                                                                        b. 10 cm if the epipedon has a texture class finer than
     a. Structural units with a diameter of 30 cm or less or            loamy fine sand (when mixed) and it is directly above a
     secondary structure with a diameter of 30 cm or less; or           densic, lithic, or paralithic contact, a petrocalcic horizon, or a
                                                                        duripan; or
     b. A moderately hard or softer rupture-resistance class; and
                                                                        c. 18 to 25 cm and the thickness is one-third or more of the
2. Rock structure, including fine stratifications (5 mm or less
                                                                        total thickness between the mineral soil surface and:
thick), in less than one-half of the volume of all parts; and
                                                                             (1) The upper boundary of the shallowest of any
3.    One of the following:
                                                                             identifiable secondary carbonates or a calcic horizon,
     a.   Both of the following:                                             petrocalcic horizon, duripan, or fragipan; and/or
8                                                                                                                Keys to Soil Taxonomy



          (2) The lower boundary of the deepest of an argillic,          A plaggen epipedon can be identified by several means.
          cambic, natric, oxic, or spodic horizon; or                 Commonly, it contains artifacts, such as bits of brick and
                                                                      pottery, throughout its depth. There may be chunks of diverse
     d.    18 cm if none of the above conditions apply; and
                                                                      materials, such as black sand and light gray sand, as large as
7.    Phosphate:                                                      the size held by a spade. The plaggen epipedon normally shows
                                                                      spade marks throughout its depth and also remnants of thin
     a. Content less than 1,500 milligrams per kilogram by
                                                                      stratified beds of sand that were probably produced on the soil
     citric-acid extraction; or
                                                                      surface by beating rains and were later buried by spading. A
     b. Content decreasing irregularly with increasing depth          map unit delineation of soils with plaggen epipedons would tend
     below the epipedon; or                                           to have straight-sided rectangular bodies that are higher than the
                                                                      adjacent soils by as much as or more than the thickness of the
     c.    Nodules are within the epipedon; and
                                                                      plaggen epipedon.
8. Some part of the epipedon is moist for 90 days or more
                                                                      Required Characteristics
(cumulative) in normal years during times when the soil
temperature at a depth of 50 cm is 5 oC or higher, if the soil is        The plaggen epipedon consists of mineral soil materials and
not irrigated; and                                                    has the following:
9. The n value (defined below) is less than 0.7.                      1. Locally raised land surfaces; and one or both of the
                                                                      following:
Ochric Epipedon                                                            a. Artifacts; or
   The ochric epipedon fails to meet the definitions for any of            b. Spade marks below a depth of 30 cm; and
the other seven epipedons because it is too thin or too dry, has
too high a color value or chroma, contains too little organic         2. Colors with a value of 4 or less, moist, 5 or less, dry, and
carbon, has too high an n value or melanic index, or is both          chroma of 2 or less; and
massive and hard or harder when dry. Many ochric epipedons            3. An organic-carbon content of 0.6 percent or more; and
have either a color value of 4 or more, moist, and 6 or more, dry,
or chroma of 4 or more, or they include an A or Ap horizon that       4. A thickness of 50 cm or more; and
has both low color values and low chroma but is too thin to be        5. Some part of the epipedon that is moist for 90 days or
recognized as a mollic or umbric epipedon (and has less than 15       more (cumulative) in normal years during times when the soil
percent calcium carbonate equivalent in the fine-earth fraction).     temperature at a depth of 50 cm is 5 oC or higher, if the soil is
Ochric epipedons also include horizons of organic materials           not irrigated.
that are too thin to meet the requirements for a histic or folistic
epipedon.                                                             Umbric Epipedon
   The ochric epipedon includes eluvial horizons that are at
or near the soil surface, and it extends to the first underlying      Required Characteristics
diagnostic illuvial horizon (defined below as an argillic,               The umbric epipedon consists of mineral soil materials and,
kandic, natric, or spodic horizon). If the underlying horizon is      after mixing of the upper 18 cm of the mineral soil or of the
a B horizon of alteration (defined below as a cambic or oxic          whole mineral soil if its depth to a densic, lithic, or paralithic
horizon) and there is no surface horizon that is appreciably          contact, a petrocalcic horizon, or a duripan (all defined below) is
darkened by humus, the lower limit of the ochric epipedon is the      less than 18 cm, has the following properties:
lower boundary of the plow layer or an equivalent depth (18 cm)
in a soil that has not been plowed. Actually, the same horizon        1. When dry, either or both:
in an unplowed soil may be both part of the epipedon and part              a. Structural units with a diameter of 30 cm or less or
of the cambic horizon; the ochric epipedon and the subsurface              secondary structure with a diameter of 30 cm or less; or
diagnostic horizons are not all mutually exclusive. The ochric
epipedon does not have rock structure and does not include                 b. A moderately hard or softer rupture-resistance class; and
finely stratified fresh sediments, nor can it be an Ap horizon        2. Rock structure, including fine stratifications (5 mm or less
directly overlying such deposits.                                     thick), in less than one-half of the volume of all parts; and
                                                                      3.    Both of the following:
Plaggen Epipedon
                                                                           a. Dominant colors with a value of 3 or less, moist, and of
  The plaggen epipedon is a human-made surface layer 50
                                                                           5 or less, dry; and
cm or more thick that has been produced by long-continued
manuring.                                                                  b.   Dominant colors with chroma of 3 or less, moist; and
Horizons and Characteristics Diagnostic for the Higher Categories                                                                             9



4. A base saturation (by NH4OAc) of less than 50 percent in               temperature at a depth of 50 cm is 5 oC or higher, if the soil is
some or all parts; and                                                    not irrigated; and
5. An organic-carbon content of:                                          9. The n value (defined below) is less than 0.7; and
     a. 0.6 percent (absolute) more than that of the C horizon            10. The umbric epipedon does not have the artifacts, spade              D
                                                                                                                                                  I
     (if one occurs) if the umbric epipedon has a color value less        marks, and raised surfaces that are characteristic of the plaggen       A
     than 1 unit lower or chroma less than 2 units lower (both            epipedon.
     moist and dry) than the C horizon; or
     b. 0.6 percent or more and the epipedon does not meet the            Diagnostic Subsurface Horizons
     qualifications in 5-a above; and
                                                                             The horizons described in this section form below the
6. The minimum thickness of the epipedon is as follows:                   surface of the soil, although in some areas they form directly
     a.    25 cm if:                                                      below a layer of leaf litter. They may be exposed at the surface
                                                                          by truncation of the soil. Some of these horizons are generally
          (1) The texture class of the epipedon is loamy fine sand
                                                                          regarded as B horizons, some are considered B horizons by
          or coarser throughout; or
                                                                          many but not all pedologists, and others are generally regarded
          (2) There are no underlying diagnostic horizons                 as parts of the A horizon.
          (defined below) and the organic-carbon content of the
          underlying materials decreases irregularly with increasing      Agric Horizon
          depth; or
                                                                              The agric horizon is an illuvial horizon that has formed
          (3) Any of the following, if present, are 75 cm or more         under cultivation and contains significant amounts of illuvial
          below the mineral soil surface:                                 silt, clay, and humus.
             (a) The upper boundary of the shallowest of any              Required Characteristics
             identifiable secondary carbonates or a calcic horizon,
             petrocalcic horizon, duripan, or fragipan (defined              The agric horizon is directly below an Ap horizon and has
             below); and/or                                               the following properties:
             (b) The lower boundary of the deepest of an argillic,        1. A thickness of 10 cm or more and either:
             cambic, natric, oxic, or spodic horizon; or
                                                                             a. 5 percent or more (by volume) wormholes, including
     b. 10 cm if the epipedon has a texture class finer than                 coatings that are 2 mm or more thick and have a value, moist,
     loamy fine sand (when mixed) and it is directly above a                 of 4 or less and chroma of 2 or less; or
     densic, lithic, or paralithic contact, a petrocalcic horizon, or a
                                                                             b. 5 percent or more (by volume) lamellae that have a
     duripan; or
                                                                             thickness of 5 mm or more and have a value, moist, of 4 or
     c. 18 to 25 cm and the thickness is one-third or more of the            less and chroma of 2 or less.
     total thickness between the mineral soil surface and:
          (1) The upper boundary of the shallowest of any                 Albic Horizon
          identifiable secondary carbonates or a calcic horizon,              The albic horizon is an eluvial horizon, 1.0 cm or more
          petrocalcic horizon, duripan, or fragipan; and/or               thick, that has 85 percent or more (by volume) albic materials
          (2) The lower boundary of the deepest of an argillic,           (defined below). It generally occurs below an A horizon but
          cambic, natric, oxic, or spodic horizon; or                     may be at the mineral soil surface. Under the albic horizon
                                                                          there generally is an argillic, cambic, kandic, natric, or spodic
     d.    18 cm if none of the above conditions apply; and
                                                                          horizon or a fragipan (defined below). The albic horizon may
7.    Phosphate:                                                          lie between a spodic horizon and either a fragipan or an argillic
                                                                          horizon, or it may be between an argillic or kandic horizon and
     a. Content less than 1,500 milligrams per kilogram by
                                                                          a fragipan. It may lie between a mollic epipedon and an argillic
     citric-acid extraction; or
                                                                          or natric horizon or between a cambic horizon and an argillic,
     b. Content decreasing irregularly with increasing depth              kandic, or natric horizon or a fragipan. The albic horizon may
     below the epipedon; or                                               separate horizons that, if they were together, would meet the
                                                                          requirements for a mollic epipedon. It may separate lamellae
     c.    Nodules are within the epipedon; and
                                                                          that together meet the requirements for an argillic horizon.
8. Some part of the epipedon is moist for 90 days or more                 These lamellae are not considered to be part of the albic
(cumulative) in normal years during times when the soil                   horizon.
10                                                                                                                     Keys to Soil Taxonomy



Argillic Horizon                                                               1.2 times more clay than the eluvial horizon; or
   An argillic horizon is normally a subsurface horizon with a                 c. If the eluvial horizon has 40 percent or more total clay
significantly higher percentage of phyllosilicate clay than the                in the fine-earth fraction, the argillic horizon must contain
overlying soil material. It shows evidence of clay illuviation.                at least 8 percent (absolute) more clay (42 percent versus 50
The argillic horizon forms below the soil surface, but it may be               percent, for example).
exposed at the surface later by erosion.
Required Characteristics                                                  Calcic Horizon
1. All argillic horizons must meet both of the following                     The calcic horizon is an illuvial horizon in which secondary
requirements:                                                             calcium carbonate or other carbonates have accumulated to a
                                                                          significant extent.
     a. One of the following:
                                                                          Required Characteristics
        (1) If the argillic horizon meets the particle-size class
        criteria for coarse-loamy, fine-loamy, coarse-silty, fine-             The calcic horizon:
        silty, fine, or very-fine or is loamy or clayey, including        1.    Is 15 cm or more thick; and
        skeletal counterparts, it must be at least 7.5 cm thick or at
        least one-tenth as thick as the sum of the thickness of all       2.    Has one or more of the following:
        overlying horizons, whichever is greater; or                           a. 15 percent or more (by weight) CaCO3 equivalent (see
        (2) If the argillic horizon meets the sandy or sandy-                  below), and its CaCO3 equivalent is 5 percent or more
        skeletal particle-size criteria, it must be at least 15 cm             (absolute) higher than that of an underlying horizon; or
        thick; or                                                              b. 15 percent or more (by weight) CaCO3 equivalent
        (3) If the argillic horizon is composed entirely of                    and 5 percent or more (by volume) identifiable secondary
        lamellae, the combined thickness of the lamellae that are              carbonates; or
        0.5 cm or more thick must be 15 cm or more; and                        c. 5 percent or more (by weight) calcium carbonate
     b. Evidence of clay illuviation in at least one of the                    equivalent and:
     following forms:                                                             (1) Has less than 18 percent clay in the fine-earth
        (1)   Oriented clay bridging the sand grains; or                          fraction; and

        (2)   Clay films lining pores; or                                         (2) Meets the criteria for a sandy, sandy-skeletal, coarse-
                                                                                  loamy, or loamy-skeletal particle-size class; and
        (3) Clay films on both vertical and horizontal surfaces
        of peds; or                                                               (3) Has 5 percent or more (by volume) identifiable
                                                                                  secondary carbonates or a calcium carbonate equivalent
        (4) Thin sections with oriented clay bodies that are more                 (by weight) that is 5 percent or more (absolute) higher
        than 1 percent of the section; or                                         than that of an underlying horizon; and
        (5) If the coefficient of linear extensibility is 0.04 or         3. Is not cemented or indurated in any part by carbonates, with
        higher and the soil has distinct wet and dry seasons, then        or without other cementing agents, or is cemented in some part
        the ratio of fine clay to total clay in the illuvial horizon is   and the cemented part satisfies one of the following:
        greater by 1.2 times or more than the ratio in the eluvial
        horizon; and                                                           a. It is characterized by so much lateral discontinuity that
                                                                               roots can penetrate through noncemented zones or along
2. If an eluvial horizon remains and there is no lithologic                    vertical fractures with a horizontal spacing of less than 10
discontinuity between it and the illuvial horizon and no plow                  cm; or
layer directly above the illuvial layer, then the illuvial horizon
must contain more total clay than the eluvial horizon within a                 b. The cemented layer is less than 1 cm thick and consists
vertical distance of 30 cm or less, as follows:                                of a laminar cap underlain by a lithic or paralithic contact; or

     a. If any part of the eluvial horizon has less than 15 percent            c. The cemented layer is less than 10 cm thick.
     total clay in the fine-earth fraction, the argillic horizon must
     contain at least 3 percent (absolute) more clay (10 percent          Cambic Horizon
     versus 13 percent, for example); or                                     A cambic horizon is the result of physical alterations,
     b. If the eluvial horizon has 15 to 40 percent total clay in         chemical transformations, or removals or of a combination of
     the fine-earth fraction, the argillic horizon must have at least     two or more of these processes.
Horizons and Characteristics Diagnostic for the Higher Categories                                                                         11



Required Characteristics                                               1. The pan is cemented or indurated in more than 50 percent
                                                                       of the volume of some horizon; and
   The cambic horizon is an altered horizon 15 cm or more
thick. If it is composed of lamellae, the combined thickness of        2. The pan shows evidence of the accumulation of opal or
the lamellae must be 15 cm or more. In addition, the cambic            other forms of silica, such as laminar caps, coatings, lenses,          D
horizon must meet all of the following:                                partly filled interstices, bridges between sand-sized grains, or        I
                                                                                                                                               A
                                                                       coatings on rock and pararock fragments; and
1. Has a texture class of very fine sand, loamy very fine sand,
or finer; and                                                          3. Less than 50 percent of the volume of air-dry fragments
                                                                       slakes in 1N HCl even during prolonged soaking, but more
2.    Shows evidence of alteration in one of the following forms:
                                                                       than 50 percent slakes in concentrated KOH or NaOH or in
     a. Aquic conditions within 50 cm of the soil surface or           alternating acid and alkali; and
     artificial drainage and all of the following:
                                                                       4. Because of lateral continuity, roots can penetrate the pan
        (1) Soil structure or the absence of rock structure,           only along vertical fractures with a horizontal spacing of 10 cm
        including fine stratifications (5 mm or less thick), in more   or more.
        than one-half of the volume; and
        (2)     Colors that do not change on exposure to air; and      Fragipan
        (3) Dominant color, moist, on faces of peds or in the          Required Characteristics
        matrix as follows:
                                                                          To be identified as a fragipan, a layer must have all of the
              (a) Value of 3 or less and chroma of 0; or               following characteristics:
              (b) Value of 4 or more and chroma of 1 or less; or       1. The layer is 15 cm or more thick; and
              (c) Any value, chroma of 2 or less, and redox            2. The layer shows evidence of pedogenesis within the horizon
              concentrations; or                                       or, at a minimum, on the faces of structural units; and
     b. Does not have the combination of aquic conditions              3. The layer has very coarse prismatic, columnar, or blocky
     within 50 cm of the soil surface or artificial drainage and       structure of any grade, has weak structure of any size, or is
     colors, moist, as defined in item 2-a-(3) above, and has soil     massive. Separations between structural units that allow roots
     structure or the absence of rock structure, including fine        to enter have an average spacing of 10 cm or more on the
     stratifications (5 mm or less thick), in more than one-half of    horizontal dimensions; and
     the volume and one or more of the following properties:
                                                                       4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in
        (1) Higher chroma, higher value, redder hue, or higher         diameter, from more than 50 percent of the layer slake when
        clay content than the underlying horizon or an overlying       they are submerged in water; and
        horizon; or
                                                                       5. The layer has, in 60 percent or more of the volume, a firm
        (2) Evidence of the removal of carbonates or gypsum;           or firmer rupture-resistance class, a brittle manner of failure at
        and                                                            or near field capacity, and virtually no roots; and
3. Has properties that do not meet the requirements for an             6. The layer is not effervescent (in dilute HCl).
anthropic, histic, folistic, melanic, mollic, plaggen, or umbric
epipedon, a duripan or fragipan, or an argillic, calcic, gypsic,       Glossic Horizon
natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon;
and                                                                       The glossic horizon (Gr. glossa, tongue) develops as a result
                                                                       of the degradation of an argillic, kandic, or natric horizon from
4. Is not part of an Ap horizon and does not have a brittle            which clay and free iron oxides are removed.
manner of failure in more than 60 percent of the matrix.
                                                                       Required Characteristics
Duripan                                                                   The glossic horizon is 5 cm or more thick and consists of:
   A duripan is a silica-cemented subsurface horizon with or
                                                                       1. An eluvial part (albic materials, defined below), which
without auxiliary cementing agents. It can occur in conjunction
                                                                       constitutes 15 to 85 percent (by volume) of the glossic horizon;
with a petrocalcic horizon.
                                                                       and
Required Characteristics
                                                                       2. An illuvial part, i.e., remnants (pieces) of an argillic,
     A duripan must meet all of the following requirements:            kandic, or natric horizon (defined below).
12                                                                                                                  Keys to Soil Taxonomy



Gypsic Horizon                                                                 (1) Between 100 cm and 200 cm from the mineral soil
                                                                               surface if the upper 100 cm meets the criteria for a sandy
   The gypsic horizon is a horizon in which gypsum has                         or sandy-skeletal particle-size class throughout; or
accumulated or been transformed to a significant extent. It
typically occurs as a subsurface horizon, but it may occur at the              (2) Within 100 cm from the mineral soil surface if
surface in some soils.                                                         the clay content in the fine-earth fraction of the surface
                                                                               horizon is 20 percent or more; or
Required Characteristics
                                                                               (3) Within 125 cm from the mineral soil surface for all
     A gypsic horizon meets all of the following requirements:
                                                                               other soils; and
1.    Is 15 cm or more thick; and
                                                                     3. Has a thickness of either:
2. Is not cemented by gypsum, with or without other
                                                                          a.    30 cm or more; or
cementing agents; is cemented and the cemented parts are
less than 5 mm thick; or is cemented but, because of lateral              b. 15 cm or more if there is a densic, lithic, paralithic, or
discontinuity, roots can penetrate along vertical fractures with a        petroferric contact within 50 cm of the mineral soil surface
horizontal spacing of less than 10 cm; and                                and the kandic horizon constitutes 60 percent or more of the
                                                                          vertical distance between a depth of 18 cm and the contact;
3. Is 5 percent or more (by weight) gypsum and has 1 percent
                                                                          and
or more (by volume) visible secondary gypsum that has either
accumulated or been transformed; and                                 4.    Has a texture class of loamy very fine sand or finer; and
4. Has a product of thickness, in cm, multiplied by the gypsum       5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by
content (percent by weight) of 150 or more. Thus, a horizon 30       1N NH4OAc pH 7) and an apparent ECEC of 12 cmol(+) or less
cm thick that is 5 percent gypsum qualifies as a gypsic horizon      per kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus
if it is 1 percent or more (by volume) visible gypsum and any        1N KCl-extractable Al) in 50 percent or more of its thickness
cementation is as described in 2 above.                              between the point where the clay increase requirements are met
                                                                     and either a depth of 100 cm below that point or a densic, lithic,
Kandic Horizon                                                       paralithic, or petroferric contact if shallower. (The percentage
                                                                     of clay is either measured by the pipette method or estimated to
Required Characteristics
                                                                     be 2.5 times [percent water retained at 1500 kPa tension minus
     The kandic horizon:                                             percent organic carbon], whichever is higher, but no more than
                                                                     100); and
1. Is a vertically continuous subsurface horizon that underlies
a coarser textured surface horizon. The minimum thickness of         6. Has a regular decrease in organic-carbon content with
the surface horizon is 18 cm after mixing or 5 cm if the textural    increasing depth, no fine stratification, and no overlying layers
transition to the kandic horizon is abrupt and there is no densic,   more than 30 cm thick that have fine stratification and/or
lithic, paralithic, or petroferric contact (defined below) within    an organic-carbon content that decreases irregularly with
50 cm of the mineral soil surface; and                               increasing depth.
2.    Has its upper boundary:
                                                                     Natric Horizon
     a. At the point where the clay percentage in the fine-earth
     fraction, increasing with depth within a vertical distance of      A natric horizon is an illuvial horizon that is normally
     15 cm or less, is either:                                       present in the subsurface and has a significantly higher
                                                                     percentage of silicate clay than the overlying horizons. It shows
        (1) 4 percent or more (absolute) higher than that in the     evidence of clay illuviation that has been accelerated by the
        surface horizon if that horizon has less than 20 percent     dispersive properties of sodium.
        total clay in the fine-earth fraction; or
                                                                     Required Characteristics
        (2) 20 percent or more (relative) higher than that in the
        surface horizon if that horizon has 20 to 40 percent total        The natric horizon:
        clay in the fine-earth fraction; or                          1.    Meets one of the following thickness requirements:
        (3) 8 percent or more (absolute) higher than that in the
                                                                          a. If the horizon meets the particle-size class criteria
        surface horizon if that horizon has more than 40 percent
                                                                          for coarse-loamy, fine-loamy, coarse-silty, fine-silty, fine,
        total clay in the fine-earth fraction; and
                                                                          or very-fine or is loamy or clayey, including skeletal
     b. At a depth:                                                       counterparts, it must be at least 7.5 cm thick or at least one-
Horizons and Characteristics Diagnostic for the Higher Categories                                                                             13



     tenth as thick as the sum of the thickness of all overlying              b. More exchangeable magnesium plus sodium than
     horizons, whichever is greater; or                                       calcium plus exchange acidity (at pH 8.2) in one or more
                                                                              horizons within 40 cm of its upper boundary if the ESP is 15
     b. If the horizon meets sandy or sandy-skeletal particle-size
                                                                              or more (or the SAR is 13 or more) in one or more horizons
     class criteria, it must be at least 15 cm thick; or
                                                                              within 200 cm of the mineral soil surface.                           D
                                                                                                                                                   I
     c. If the horizon is composed entirely of lamellae, the                                                                                       A
     combined thickness of the lamellae that are 0.5 cm or more
     thick must be 15 cm or more; and                                    Ortstein
2. Has evidence of clay illuviation in at least one of the               Required Characteristics
following forms:                                                              Ortstein has all of the following:
     a.   Oriented clay bridging the sand grains; or                     1.    Consists of spodic materials; and
     b.   Clay films lining pores; or                                    2.    Is in a layer that is 50 percent or more cemented; and
     c. Clay films on both vertical and horizontal surfaces of
                                                                         3.    Is 25 mm or more thick.
     peds; or
     d. Thin sections with oriented clay bodies that are more
                                                                         Oxic Horizon
     than 1 percent of the section; or
                                                                         Required Characteristics
     e. If the coefficient of linear extensibility is 0.04 or higher
     and the soil has distinct wet and dry seasons, then the ratio of       The oxic horizon is a subsurface horizon that does not
     fine clay to total clay in the illuvial horizon is greater by 1.2   have andic soil properties (defined below) and has all of the
     times or more than the ratio in the eluvial horizon; and            following characteristics:
3. If an eluvial horizon remains and there is no lithologic              1. A thickness of 30 cm or more; and
discontinuity between it and the illuvial horizon and no plow
layer directly above the illuvial horizon, then the illuvial horizon     2. A texture class of sandy loam or finer in the fine-earth
must contain more total clay than the eluvial horizon within a           fraction; and
vertical distance of 30 cm or less, as follows:                          3. Less than 10 percent weatherable minerals in the 50- to
     a. If any part of the eluvial horizon has less than 15 percent      200-micron fraction; and
     total clay in the fine-earth fraction, the illuvial horizon must
                                                                         4. Rock structure in less than 5 percent of its volume, unless
     contain at least 3 percent (absolute) more clay (10 percent
                                                                         the lithorelicts with weatherable minerals are coated with
     versus 13 percent, for example); or
                                                                         sesquioxides; and
     b. If the eluvial horizon has 15 to 40 percent total clay in
                                                                         5. A diffuse upper boundary, i.e., within a vertical distance
     the fine-earth fraction, the illuvial horizon must have at least
                                                                         of 15 cm, a clay increase with increasing depth of:
     1.2 times more clay than the eluvial horizon; or
     c. If the eluvial horizon has 40 percent or more total clay              a. Less than 4 percent (absolute) in its fine-earth fraction
     in the fine-earth fraction, the illuvial horizon must contain            if the fine-earth fraction of the surface horizon contains less
     at least 8 percent (absolute) more clay (42 percent versus 50            than 20 percent clay; or
     percent, for example); and                                               b. Less than 20 percent (relative) in its fine-earth fraction if
4.    Has either:                                                             the fine-earth fraction of the surface horizon contains 20 to
                                                                              40 percent clay; or
     a. Columnar or prismatic structure in some part (generally
     the upper part), which may part to blocky structure; or                  c. Less than 8 percent (absolute) in its fine-earth fraction
                                                                              if the fine-earth fraction of the surface horizon contains 40
     b. Both blocky structure and eluvial materials, which                    percent or more clay); and
     contain uncoated silt or sand grains and extend more than 2.5
     cm into the horizon; and                                            6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N
                                                                         NH4OAc pH 7) and an apparent ECEC of 12 cmol(+) or less per
5.    Has either:                                                        kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus 1N
     a. An exchangeable sodium percentage (ESP) of 15 percent            KCl-extractable Al). (The percentage of clay is either measured
     or more (or a sodium adsorption ratio [SAR] of 13 or more)          by the pipette method or estimated to be 3 times [percent water
     in one or more horizons within 40 cm of its upper boundary;         retained at 1500 kPa tension minus percent organic carbon],
     or                                                                  whichever value is higher, but no more than 100.)
14                                                                                                           Keys to Soil Taxonomy



Petrocalcic Horizon                                                manganese and organic matter, with or without other cementing
                                                                   agents; and
   The petrocalcic horizon is an illuvial horizon in which
secondary calcium carbonate or other carbonates have               2. Because of lateral continuity, roots can penetrate only along
accumulated to the extent that the horizon is cemented or          vertical fractures with a horizontal spacing of 10 cm or more;
indurated.                                                         and
Required Characteristics                                           3. The horizon has a minimum thickness of 1 mm and, where
                                                                   associated with spodic materials, is less than 25 mm thick.
     A petrocalcic horizon must meet the following requirements:
1. The horizon is cemented or indurated by carbonates, with or     Salic Horizon
without silica or other cementing agents; and
                                                                     A salic horizon is a horizon of accumulation of salts that are
2. Because of lateral continuity, roots can penetrate only along   more soluble than gypsum in cold water.
vertical fractures with a horizontal spacing of 10 cm or more;
and                                                                Required Characteristics
3. The horizon has a thickness of:                                    A salic horizon is 15 cm or more thick and has, for 90
                                                                   consecutive days or more in normal years:
     a.   10 cm or more; or
                                                                   1. An electrical conductivity (EC) equal to or greater than 30
     b. 1 cm or more if it consists of a laminar cap directly
                                                                   dS/m in the water extracted from a saturated paste; and
     underlain by bedrock.
                                                                   2. A product of the EC, in dS/m, and thickness, in cm, equal to
Petrogypsic Horizon                                                900 or more.

    The petrogypsic horizon is a horizon in which visible
secondary gypsum has accumulated or has been transformed.          Sombric Horizon
The horizon is cemented (i.e., extremely weakly through                A sombric horizon (F. sombre, dark) is a subsurface horizon
indurated cementation classes), and the cementation is both        in mineral soils that has formed under free drainage. It contains
laterally continuous and root limiting, even when the soil is      illuvial humus that is neither associated with aluminum, as is
moist. The horizon typically occurs as a subsurface horizon, but   the humus in the spodic horizon, nor dispersed by sodium, as
it may occur at the surface in some soils.                         is common in the natric horizon. Consequently, the sombric
Required Characteristics                                           horizon does not have the high cation-exchange capacity in its
                                                                   clay that characterizes a spodic horizon and does not have the
   A petrogypsic horizon meets all of the following                high base saturation of a natric horizon. It does not underlie an
requirements:                                                      albic horizon.
1. Is cemented or indurated by gypsum, with or without other           Sombric horizons are thought to be restricted to the cool,
cementing agents; and                                              moist soils of high plateaus and mountains in tropical or
                                                                   subtropical regions. Because of strong leaching, their base
2. Because of lateral continuity, can be penetrated by roots       saturation is low (less than 50 percent by NH4OAc).
only along vertical fractures with a horizontal spacing of 10 cm       The sombric horizon has a lower color value or chroma,
or more; and                                                       or both, than the overlying horizon and commonly contains
3.    Is 5 mm or more thick; and                                   more organic matter. It may have formed in an argillic, cambic,
                                                                   or oxic horizon. If peds are present, the dark colors are most
4.    Is 40 percent or more (by weight) gypsum.                    pronounced on surfaces of peds.
                                                                       In the field a sombric horizon is easily mistaken for a buried
Placic Horizon                                                     A horizon. It can be distinguished from some buried epipedons
                                                                   by lateral tracing. In thin sections the organic matter of a
   The placic horizon (Gr. base of plax, flat stone; meaning a
                                                                   sombric horizon appears more concentrated on peds and in
thin cemented pan) is a thin, black to dark reddish pan that is
                                                                   pores than uniformly dispersed throughout the matrix.
cemented by iron (or iron and manganese) and organic matter.
Required Characteristics
                                                                   Spodic Horizon
     A placic horizon must meet the following requirements:
                                                                      A spodic horizon is an illuvial layer with 85 percent or more
1. The horizon is cemented or indurated with iron or iron and      spodic materials (defined below).
Horizons and Characteristics Diagnostic for the Higher Categories                                                                      15



Required Characteristics                                              1.    Chroma of 2 or less; and either
   A spodic horizon is normally a subsurface horizon                       a. A color value, moist, of 3 and a color value, dry, of 6 or
underlying an O, A, Ap, or E horizon. It may, however, meet the            more; or
definition of an umbric epipedon.
                                                                           b. A color value, moist, of 4 or more and a color value, dry,    D
   A spodic horizon must have 85 percent or more spodic                                                                                     I
                                                                           of 5 or more; or                                                 A
materials in a layer 2.5 cm or more thick that is not part of any
Ap horizon.                                                           2.    Chroma of 3 or less; and either
                                                                           a. A color value, moist, of 6 or more; or
Diagnostic Soil Characteristics for Mineral                                b. A color value, dry, of 7 or more; or
   Soils                                                              3. Chroma that is controlled by the color of uncoated grains of
   Diagnostic soil characteristics are features of the soil that      silt or sand, hue of 5YR or redder, and the color values listed in
are used in various places in the keys or in the definitions of       item 1-a or 1-b above.
diagnostic horizons.                                                      Relatively unaltered layers of light colored sand, volcanic
                                                                      ash, or other materials deposited by wind or water are not
Abrupt Textural Change                                                considered albic materials, although they may have the same
    An abrupt textural change is a specific kind of change that       color and apparent morphology. These deposits are parent
may occur between an ochric epipedon or an albic horizon              materials that are not characterized by the removal of clay
and an argillic horizon. It is characterized by a considerable        and/or free iron and do not overlie an illuvial horizon or other
increase in clay content within a very short vertical distance in     soil horizon, except for a buried soil. Light colored krotovinas
the zone of contact. If the clay content in the fine-earth fraction   or filled root channels should be considered albic materials only
of the ochric epipedon or albic horizon is less than 20 percent,      if they have no fine stratifications or lamellae, if any sealing
it doubles within a vertical distance of 7.5 cm or less. If the       along the krotovina walls has been destroyed, and if these
clay content in the fine-earth fraction of the ochric epipedon or     intrusions have been leached of free iron oxides and/or clay
the albic horizon is 20 percent or more, there is an increase of      after deposition.
20 percent or more (absolute) within a vertical distance of 7.5
cm or less (e.g., an increase from 22 to 42 percent) and the clay     Andic Soil Properties
content in some part of the argillic horizon is 2 times or more
the amount contained in the overlying horizon.                           Andic soil properties commonly form during weathering of
    Normally, there is no transitional horizon between an             tephra or other parent materials containing a significant content
ochric epipedon or an albic horizon and an argillic horizon,          of volcanic glass. Soils that are in cool, humid climates and
or the transitional horizon is too thin to be sampled. Some           have abundant organic carbon, however, may develop andic soil
soils, however, have a glossic horizon or interfingering of           properties without the influence of volcanic glass. A suite of
albic materials (defined below) in parts of the argillic horizon.     glass and glass-coated minerals rich in silica is termed volcanic
The upper boundary of such a horizon is irregular or even             glass in this taxonomy. These minerals are relatively soluble and
discontinuous. Sampling this mixture as a single horizon might        undergo fairly rapid transformation when the soils are moist.
create the impression of a relatively thick transitional horizon,     Andic soil properties represent a stage in transition where
whereas the thickness of the actual transition at the contact may     weathering and transformation of primary alumino-silicates
be no more than 1 mm.                                                 (e.g., volcanic glass) have proceeded only to the point of the
                                                                      formation of short-range-order materials, such as allophane,
                                                                      imogolite, and ferrihydrite, or of metal-humus complexes. The
Albic Materials
                                                                      concept of andic soil properties includes moderately weathered
   Albic (L. albus, white) materials are soil materials with a        soil material, rich in short-range-order materials or metal-
color that is largely determined by the color of primary sand         humus complexes, or both, with or without volcanic glass
and silt particles rather than by the color of their coatings.        (required characteristic 2) and weakly weathered soil, less rich
This definition implies that clay and/or free iron oxides have        in short-range-order materials with volcanic glass (required
been removed from the materials or that the oxides have been          characteristic 3).
segregated to such an extent that the color of the materials is          Relative amounts of allophane, imogolite, ferrihydrite, or
largely determined by the color of the primary particles.             metal-humus complexes in the colloidal fraction are inferred
                                                                      from laboratory analyses of aluminum, iron, and silica extracted
Required Characteristics
                                                                      by ammonium oxalate, and from phosphate retention. Soil
   Albic materials have one of the following colors:                  scientists may use smeariness or pH in 1N sodium fluoride
16                                                                                                                        Keys to Soil Taxonomy



                                                                             3.    All of the following:
                                                                                  a. 30 percent or more of the fine-earth fraction is 0.02 to
                                                                                  2.0 mm in size; and
                                                                                  b. Phosphate retention of 25 percent or more; and
                                                                                  c. Al + ½ Fe content (by ammonium oxalate) equal to 0.4
                                                                                  percent or more; and
                                                                                  d. Volcanic glass content of 5 percent or more; and
                                                                                  e. [(Al + ½ Fe content, percent) times (15.625)] + [volcanic
                                                                                  glass content, percent] = 36.25 or more.
                                                                                  The shaded area in figure 1 illustrates criteria 3c, 3d, and 3e.

                                                                             Anhydrous Conditions
                                                                                Anhydrous conditions (Gr. anydros, waterless) refer to
                                                                             the moisture condition of soils in very cold deserts and other
                                                                             areas with permafrost (often dry permafrost). These soils
                                                                             typically have low precipitation (usually less than 50 mm water
                                                                             equivalent per year) and a moisture content of less than 3
                                                                             percent by weight. Anhydrous soil conditions are similar to the
                                                                             aridic (torric) soil moisture regimes (defined below), except that
                                                                             the soil temperature at 50 cm is less than 5 oC throughout the
                                                                             year in the soil layers with these conditions.

                                                                             Required Characteristics
Figure 1.—Soils that are plotted in the shaded area meet the andic              Soils with anhydrous conditions have a mean annual soil
     soil properties criteria c, d, and e under item 3 of the required       temperature of 0 oC or colder. The layer from 10 to 70 cm
     characteristics. To qualify as soils with andic properties, the soils   below the soil surface has a soil temperature of less than 5 oC
     must also meet the listed requirements for organic-carbon content,
                                                                             throughout the year and this layer:
     phosphate retention, and particle-size distribution.
                                                                             1.    Includes no ice-cemented permafrost; and

(NaF) as field indicators of andic soil properties. Volcanic                 2. Is dry (water held at 1500 kPa or more) in one-half or more
glass content is the percent volcanic glass (by grain count) in              of the soil for one-half or more of the time the layer has a soil
the coarse silt and sand (0.02 to 2.0 mm) fraction. Most soil                temperature above 0 oC; or
materials with andic soil properties consist of mineral soil                 3. Has a rupture-resistance class of loose to slightly hard
materials, but some are organic soil materials with less than 25             throughout when the soil temperature is 0 oC or colder, except
percent organic carbon.                                                      where a cemented pedogenic horizon occurs.
Required Characteristics
                                                                             Coefficient of Linear Extensibility (COLE)
   Soil materials with andic soil properties must have a fine-
earth fraction that meets the following requirements:                           The coefficient of linear extensibility (COLE) is the ratio
                                                                             of the difference between the moist length and dry length of a
1. Less than 25 percent organic carbon (by weight) and one or                clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the length
both of the following:                                                       at 33 kPa tension and Ld is the length when dry. COLE can be
2.    All of the following:                                                  calculated from the differences in bulk density of the clod when
                                                                             moist and when dry. An estimate of COLE can be calculated in
     a. Bulk density, measured at 33 kPa water retention, of 0.90            the field by measuring the distance between two pins in a clod
     g/cm3 or less; and                                                      of undisturbed soil at field capacity and again after the clod has
     b.   Phosphate retention of 85 percent or more; and                     dried. COLE does not apply if the shrinkage is irreversible.

     c. Al + ½ Fe content (by ammonium oxalate) equal to 2.0
     percent or more; or
Horizons and Characteristics Diagnostic for the Higher Categories                                                                   17



Durinodes                                                           with cold, dilute HCl. The term “free carbonates” is nearly
                                                                    synonymous with the term “calcareous.” Soils that have free
   Durinodes (L. durus, hard, and nodus, knot) are weakly           carbonates generally have calcium carbonate as a common
cemented to indurated nodules or concretions with a diameter        mineral, although sodium and magnesium carbonates are also
of 1 cm or more. The cement is SiO2, presumably opal and            included in this concept. Soils or horizons with free carbonates      D
microcrystalline forms of silica. Durinodes break down in           may have inherited the carbonate compounds from parent
                                                                                                                                          I
                                                                                                                                          A
hot concentrated KOH after treatment with HCl to remove             materials without any translocation or transformation processes
carbonates but do not break down with concentrated HCl alone.       acting on them. There is no implication of pedogenesis in the
Dry durinodes do not slake appreciably in water, but prolonged      concept of free carbonates, as there is in identifiable secondary
soaking can result in spalling of very thin platelets. Durinodes    carbonates (defined below), although most forms of secondary
are firm or firmer and brittle when wet, both before and after      carbonates are freely effervescent.
treatment with acid. Some durinodes are roughly concentric
when viewed in cross section, and concentric stringers of opal
are visible under a hand lens.                                      Identifiable Secondary Carbonates
                                                                        The term “identifiable secondary carbonates” is used in
Fragic Soil Properties                                              the definitions of a number of taxa. It refers to translocated
    Fragic soil properties are the essential properties of a        authigenic calcium carbonate that has been precipitated in place
fragipan. They have neither the layer thickness nor volume          from the soil solution rather than inherited from a soil parent
requirements for the fragipan. Fragic soil properties are in        material, such as calcareous loess or limestone residuum.
subsurface horizons, although they can be at or near the surface        Identifiable secondary carbonates either may disrupt the soil
in truncated soils. Aggregates with fragic soil properties have     structure or fabric, forming masses, nodules, concretions, or
a firm or firmer rupture-resistance class and a brittle manner      spheroidal aggregates (white eyes) that are soft and powdery
of failure when soil water is at or near field capacity. Air-dry    when dry, or may be present as coatings in pores, on structural
fragments of the natural fabric, 5 to 10 cm in diameter, slake      faces, or on the undersides of rock or pararock fragments. If
when they are submerged in water. Aggregates with fragic soil       present as coatings, the secondary carbonates cover a significant
properties show evidence of pedogenesis, including one or more      part of the surfaces. Commonly, they coat all of the surfaces
of the following: oriented clay within the matrix or on faces of    to a thickness of 1 mm or more. If little calcium carbonate is
peds, redoximorphic features within the matrix or on faces of       present in the soil, however, the surfaces may be only partially
peds, strong or moderate soil structure, and coatings of albic      coated. The coatings must be thick enough to be visible when
materials or uncoated silt and sand grains on faces of peds or in   moist. Some horizons are entirely engulfed by carbonates. The
seams. Peds with these properties are considered to have fragic     color of these horizons is largely determined by the carbonates.
soil properties regardless of whether or not the density and        The carbonates in these horizons are within the concept of
brittleness are pedogenic.                                          identifiable secondary carbonates.
    Soil aggregates with fragic soil properties must:                   The filaments commonly seen in a dry calcareous horizon are
                                                                    within the meaning of identifiable secondary carbonates if the
1. Show evidence of pedogenesis within the aggregates or, at a      filaments are thick enough to be visible when the soil is moist.
minimum, on the faces of the aggregates; and                        Filaments commonly branch on structural faces.
2. Slake when air-dry fragments of the natural fabric, 5 to 10
cm in diameter, are submerged in water; and                         Interfingering of Albic Materials
3. Have a firm or firmer rupture-resistance class and a brittle         The term “interfingering of albic materials” refers to albic
manner of failure when soil water is at or near field capacity;     materials that penetrate 5 cm or more into an underlying
and                                                                 argillic, kandic, or natric horizon along vertical and, to a lesser
4. Restrict the entry of roots into the matrix when soil water is   degree, horizontal faces of peds. There need not be a continuous
at or near field capacity.                                          overlying albic horizon. The albic materials constitute less
                                                                    than 15 percent of the layer that they penetrate, but they form
                                                                    continuous skeletans (ped coatings of clean silt or sand defined
Free Carbonates                                                     by Brewer, 1976) 1 mm or more thick on the vertical faces of
    The term “free carbonates” is used in the definitions of a      peds, which means a total width of 2 mm or more between
number of taxa, is used as a criterion for the isotic mineralogy    abutting peds. Because quartz is such a common constituent of
class, and is mentioned in the discussion of chemical analyses      silt and sand, these skeletans are usually light gray when moist
in the Appendix. It refers to soil carbonates that are uncoated     and nearly white when dry, but their color is determined in large
or unbound and that effervesce visibly or audibly when treated      part by the color of the sand or silt fraction.
18                                                                                                                Keys to Soil Taxonomy



Required Characteristics                                               all soil horizons. Linear extensibility is a criterion for most
                                                                       Vertic subgroups in this taxonomy and is calculated as summed
  Interfingering of albic materials is recognized if albic
                                                                       products from the mineral soil surface to a depth of 100 cm or
materials:
                                                                       to a root-limiting layer.
1. Penetrate 5 cm or more into an underlying argillic or natric
horizon; and                                                           Lithologic Discontinuities
2. Are 2 mm or more thick between vertical faces of abutting               Lithologic discontinuities are significant changes in particle-
peds; and                                                              size distribution or mineralogy that represent differences in
3. Constitute less than 15 percent (by volume) of the layer that       lithology within a soil. A lithologic discontinuity can also
they penetrate.                                                        denote an age difference. For information on using horizon
                                                                       designations for lithologic discontinuities, see the Soil Survey
                                                                       Manual (USDA, SCS, 1993).
Lamellae                                                                   Not everyone agrees on the degree of change required for
   A lamella is an illuvial horizon less than 7.5 cm thick. Each       a lithologic discontinuity. No attempt is made to quantify
lamella contains an accumulation of oriented silicate clay on          lithologic discontinuities. The discussion below is meant to
or bridging sand and silt grains (and rock fragments if any are        serve as a guideline.
present). A lamella has more silicate clay than the overlying              Several lines of field evidence can be used to evaluate
eluvial horizon.                                                       lithologic discontinuities. In addition to mineralogical and
                                                                       textural differences that may require laboratory studies, certain
Required Characteristics                                               observations can be made in the field. These include but are not
   A lamella is an illuvial horizon less than 7.5 cm thick formed      limited to the following:
in unconsolidated regolith more than 50 cm thick. Each lamella             1. Abrupt textural contacts.—An abrupt change in
contains an accumulation of oriented silicate clay on or bridging      particle-size distribution, which is not solely a change in clay
the sand and silt grains (and rock fragments if any are present).      content resulting from pedogenesis, can often be observed.
Each lamella is required to have more silicate clay than the               2. Contrasting sand sizes.—Significant changes in sand
overlying eluvial horizon.                                             size can be detected. For example, if material containing mostly
   Lamellae occur in a vertical series of two or more, and each        medium sand or finer sand abruptly overlies material containing
lamella must have an overlying eluvial horizon. (An eluvial            mostly coarse sand and very coarse sand, one can assume that
horizon is not required above the uppermost lamella if the soil is     there are two different materials. Although the materials may be
truncated.)                                                            of the same mineralogy, the contrasting sand sizes result from
   Lamellae may meet the requirements for either a cambic or           differences in energy at the time of deposition by water and/or
an argillic horizon. A combination of two or more lamellae 15          wind.
cm or more thick is a cambic horizon if the texture class is               3. Bedrock lithology vs. rock fragment lithology in the
very fine sand, loamy very fine sand, or finer. A combination          soil.—If a soil with rock fragments overlies a lithic contact, one
of two or more lamellae meets the requirements for an argillic         would expect the rock fragments to have a lithology similar to
horizon if there is 15 cm or more cumulative thickness of              that of the material below the lithic contact. If many of the rock
lamellae that are 0.5 cm or more thick and that have a clay            fragments do not have the same lithology as the underlying
content of either:                                                     bedrock, the soil is not derived completely from the underlying
                                                                       bedrock.
1. 3 percent or more (absolute) higher than in the overlying               4. Stone lines.—The occurrence of a horizontal line of
eluvial horizon (e.g., 13 percent versus 10 percent) if any part of    rock fragments in the vertical sequence of a soil indicates that
the eluvial horizon has less than 15 percent clay in the fine-earth    the soil may have developed in more than one kind of parent
fraction; or                                                           material. The material above the stone line is most likely
2. 20 percent or more (relative) higher than in the overlying          transported, and the material below may be of different origin.
eluvial horizon (e.g., 24 percent versus 20 percent) if all parts of       5. Inverse distribution of rock fragments.—A lithologic
the eluvial horizon have more than 15 percent clay in the fine-        discontinuity is often indicated by an erratic distribution of rock
earth fraction.                                                        fragments. The percentage of rock fragments decreases with
                                                                       increasing depth. This line of evidence is useful in areas of soils
                                                                       that have relatively unweathered rock fragments.
Linear Extensibility (LE)
                                                                           6. Rock fragment weathering rinds.—Horizons
   Linear extensibility (LE) helps to predict the potential of a       containing rock fragments with no rinds that overlie horizons
soil to shrink and swell. The LE of a soil layer is the product        containing rocks with rinds suggest that the upper material is in
of the thickness, in cm, multiplied by the COLE of the layer           part depositional and not related to the lower part in time and
in question. The LE of a soil is the sum of these products for         perhaps in lithology.
Horizons and Characteristics Diagnostic for the Higher Categories                                                                       19



   7. Shape of rock fragments.—A soil with horizons                                      n = (A - 0.2R)/(L + 3H)
containing angular rock fragments overlying horizons                       In this formula, A is the percentage of water in the soil
containing well rounded rock fragments may indicate a                  in field condition, calculated on a dry-soil basis; R is the
discontinuity. This line of evidence represents different              percentage of silt plus sand; L is the percentage of clay; and
mechanisms of transport (colluvial vs. alluvial) or even different     H is the percentage of organic matter (percent organic carbon         D
                                                                                                                                             I
transport distances.                                                   multiplied by 1.724).                                                 A
   8. Soil color.—Abrupt changes in color that are not the                 Few data for calculations of the n value are available
result of pedogenic processes can be used as indicators of             in the United States, but the critical n value of 0.7 can be
discontinuity.                                                         approximated closely in the field by a simple test of squeezing
   9. Micromorphological features.—Marked differences in               a soil sample in the palm of a hand. If the soil flows between
the size and shape of resistant minerals in one horizon and not        the fingers with difficulty, the n value is between 0.7 and 1.0
in another are indicators of differences in materials.                 (slightly fluid manner of failure class); if the soil flows easily
                                                                       between the fingers, the n value is 1 or more (moderately fluid
Use of Laboratory Data
                                                                       or very fluid manner of failure class); and if no soil material
    Discontinuities are not always readily apparent in the field. In   flows through the fingers during full compression, the sample
these cases laboratory data are necessary. Even with laboratory        has an n value less than 0.7 (nonfluid manner of failure class).
data, detecting discontinuities may be difficult. The decision is
a qualitative or perhaps a partly quantitative judgment. General       Petroferric Contact
concepts of lithology as a function of depth might include:
    1. Laboratory data—visual scan.—The array of                           A petroferric (Gr. petra, rock, and L. ferrum, iron; implying
laboratory data is assessed in an attempt to determine if a field-     ironstone) contact is a boundary between soil and a continuous
designated discontinuity is corroborated and if any data show          layer of indurated material in which iron is an important cement
evidence of a discontinuity not observed in the field. One must        and organic matter is either absent or present only in traces. The
sort changes in lithology from changes caused by pedogenic             indurated layer must be continuous within the limits of each
processes. In most cases the quantities of sand and coarser            pedon, but it may be fractured if the average lateral distance
fractions are not altered significantly by soil-forming processes.     between fractures is 10 cm or more. The fact that this ironstone
Therefore, an abrupt change in sand size or sand mineralogy            layer contains little or no organic matter distinguishes it from a
is a clue to lithologic change. Gross soil mineralogy and the          placic horizon and an indurated spodic horizon (ortstein), both
resistant mineral suite are other clues.                               of which contain organic matter.
    2. Data on a clay-free basis.—A common manipulation                    Several features can aid in making the distinction between
in assessing lithologic change is computation of sand and silt         a lithic contact and a petroferric contact. First, a petroferric
separates on a carbonate-free, clay-free basis (percent fraction,      contact is roughly horizontal. Second, the material directly
e.g., fine sand and very fine sand, divided by percent sand plus       below a petroferric contact contains a high amount of iron
silt, times 100). Clay distribution is subject to pedogenic change     (normally 30 percent or more Fe2O3). Third, the ironstone sheets
and may either mask inherited lithologic differences or produce        below a petroferric contact are thin; their thickness ranges
differences that are not inherited from lithology. The numerical       from a few centimeters to very few meters. Sandstone, on the
array computed on a clay-free basis can be inspected visually or       other hand, may be thin or very thick, may be level-bedded or
plotted as a function of depth.                                        tilted, and may contain only a small percentage of Fe2O3. In the
    Another aid used to assess lithologic changes is computation       Tropics, the ironstone is generally more or less vesicular.
of the ratios of one sand separate to another. The ratios can
be computed and examined as a numerical array, or they can             Plinthite
be plotted. The ratios work well if sufficient quantities of the
two fractions are available. Low quantities magnify changes in             Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor
ratios, especially if the denominator is low.                          mixture of clay with quartz and other minerals. It commonly
                                                                       occurs as dark red redox concentrations that usually form platy,
                                                                       polygonal, or reticulate patterns. Plinthite changes irreversibly
n Value                                                                to an ironstone hardpan or to irregular aggregates on exposure
   The n value (Pons and Zonneveld, 1965) characterizes the            to repeated wetting and drying, especially if it is also exposed
relation between the percentage of water in a soil under field         to heat from the sun. The lower boundary of a zone in which
conditions and its percentages of inorganic clay and humus.            plinthite occurs generally is diffuse or gradual, but it may be
The n value is helpful in predicting whether a soil can be grazed      abrupt at a lithologic discontinuity.
by livestock or can support other loads and in predicting what             Plinthite may occur as a constituent of a number of horizons,
degree of subsidence would occur after drainage.                       such as an epipedon, a cambic horizon, an argillic horizon, an
   For mineral soil materials that are not thixotropic, the n value    oxic horizon, or a C horizon. It is one form of the material that
can be calculated by the following formula:                            has been called laterite. It normally forms in a horizon below
20                                                                                                                Keys to Soil Taxonomy



the surface, but it may form at the surface in a seep area at the       mm fraction. Examples are quartz, zircon, tourmaline, beryl,
base of a slope.                                                        anatase, rutile, iron oxides and oxyhydroxides, 1:1 dioctahedral
    From a genetic viewpoint, plinthite forms by segregation            phyllosilicates (kandites), gibbsite, and hydroxy-aluminum
of iron. In many places iron probably has been added from               interlayered 2:1 minerals (Burt, 2004).
other horizons or from the higher adjacent soils. Generally,
plinthite forms in a horizon that is saturated with water for           Slickensides
some time during the year. Initially, iron is normally segregated
in the form of soft, more or less clayey, red or dark red redox             Slickensides are polished and grooved surfaces and generally
concentrations. These concentrations are not considered                 have dimensions exceeding 5 cm. They are produced when
plinthite unless there has been enough segregation of iron to           one soil mass slides past another. Some slickensides occur
permit their irreversible hardening on exposure to repeated             at the lower boundary of a slip surface where a mass of soil
wetting and drying.                                                     moves downward on a relatively steep slope. Slickensides result
    Plinthite is firm or very firm when the soil moisture content       directly from the swelling of clay minerals and shear failure.
is near field capacity and hard when the moisture content is            They are very common in swelling clays that undergo marked
below the wilting point. Plinthite occurs as discrete bodies            changes in moisture content.
larger than 2 mm that can be separated from the matrix. A moist
aggregate of plinthite will withstand moderate rolling between          Spodic Materials
thumb and forefinger and is less than strongly cemented. Moist              Spodic materials form in an illuvial horizon that normally
or air-dried plinthite will not slake when submerged in water           underlies a histic, ochric, or umbric epipedon or an albic
even with gentle agitation. Plinthite does not harden irreversibly      horizon. In most undisturbed areas, spodic materials underlie an
as a result of a single cycle of drying and rewetting. After a          albic horizon. They may occur within an umbric epipedon or an
single drying, it will remoisten and then can be dispersed in           Ap horizon.
large part if one shakes it in water with a dispersing agent.               A horizon consisting of spodic materials normally has an
    In a moist soil, plinthite is soft enough to be cut with a spade.   optical-density-of-oxalate-extract (ODOE) value of 0.25 or
After irreversible hardening, it is no longer considered plinthite      more, and that value is commonly at least 2 times as high as the
but is called ironstone. Indurated ironstone materials can be           ODOE value in an overlying eluvial horizon. This increase in
broken or shattered with a spade but cannot be dispersed if one         ODOE value indicates an accumulation of translocated organic
shakes them in water with a dispersing agent.                           materials in an illuvial horizon. Soils with spodic materials
    A small amount of plinthite in the soil does not form a             show evidence that organic materials and aluminum, with or
continuous phase; that is, the individual redox concentrations          without iron, have been moved from an eluvial horizon to an
or aggregates are not connected with each other. If a large             illuvial horizon.
amount of plinthite is present, it may form a continuous phase.
Individual aggregates of plinthite in a continuous phase are            Definition of Spodic Materials
interconnected, and the spacing of cracks or zones that roots can          Spodic materials are mineral soil materials that do not
enter is 10 cm or more.                                                 have all of the properties of an argillic or kandic horizon; are
    If a continuous layer becomes indurated, it is a massive            dominated by active amorphous materials that are illuvial and
ironstone layer that has irregular, somewhat tubular inclusions         are composed of organic matter and aluminum, with or without
of yellowish, grayish, or white, clayey material. If the layer          iron; and have both of the following:
is exposed, these inclusions may be washed out, leaving an
ironstone that has many coarse, tubular pores.                          1. A pH value in water (1:1) of 5.9 or less and an organic-
    Much that has been called laterite is included in the               carbon content of 0.6 percent or more; and
meaning of plinthite. Doughy and concretionary laterite that            2.    One or both of the following:
has not hardened is an example. Hardened laterite, whether
it is vesicular or pisolitic, is not included in the definition of           a. An overlying albic horizon that extends horizontally
plinthite.                                                                   through 50 percent or more of each pedon and, directly
                                                                             under the albic horizon, colors, moist (crushed and smoothed
                                                                             sample), as follows:
Resistant Minerals
                                                                               (1)   Hue of 5YR or redder; or
   Several references are made to resistant minerals in this
taxonomy. Obviously, the stability of a mineral in the soil is a               (2) Hue of 7.5YR, color value of 5 or less, and chroma
partial function of the soil moisture regime. Where resistant                  of 4 or less; or
minerals are referred to in the definitions of diagnostic horizons
                                                                               (3) Hue of 10YR or neutral and a color value and
and of various taxa, a humid climate, past or present, is always
                                                                               chroma of 2 or less; or
assumed.
   Resistant minerals are durable minerals in the 0.02 to 2.0                  (4) A color of 10YR 3/1; or
Horizons and Characteristics Diagnostic for the Higher Categories                                                                          21



   b. With or without an albic horizon and one of the colors                Obviously, this definition of the term “weatherable minerals”
   listed above or hue of 7.5YR, color value, moist, of 5 or less,      is restrictive. The intent is to include, in the definitions of
   chroma of 5 or 6 (crushed and smoothed sample), and one or           diagnostic horizons and various taxa, only those weatherable
   more of the following morphological or chemical properties:          minerals that are unstable in a humid climate compared to
                                                                        other minerals, such as quartz and 1:1 lattice clays, but that are      D
      (1) Cementation by organic matter and aluminum, with                                                                                      I
                                                                        more resistant to weathering than calcite. Calcite, carbonate           A
      or without iron, in 50 percent or more of each pedon
                                                                        aggregates, gypsum, and halite are not considered weatherable
      and a very firm or firmer rupture-resistance class in the
                                                                        minerals because they are mobile in the soil. They appear to be
      cemented part; or
                                                                        recharged in some otherwise strongly weathered soils.
      (2)   10 percent or more cracked coatings on sand grains;
      or
      (3) Al + 1/2 Fe percentages (by ammonium oxalate)
                                                                        Characteristics Diagnostic for
      totaling 0.50 or more, and half that amount or less in an           Organic Soils
      overlying umbric (or subhorizon of an umbric) epipedon,
                                                                           Following is a description of the characteristics that are used
      ochric epipedon, or albic horizon; or
                                                                        only with organic soils.
      (4) An optical-density-of-oxalate-extract (ODOE) value
      of 0.25 or more, and a value half as high or lower in an          Kinds of Organic Soil Materials
      overlying umbric (or subhorizon of an umbric) epipedon,
      ochric epipedon, or albic horizon.                                   Three different kinds of organic soil materials are
                                                                        distinguished in this taxonomy, based on the degree of
Volcanic Glass                                                          decomposition of the plant materials from which the organic
                                                                        materials are derived. The three kinds are (1) fibric, (2) hemic,
    Volcanic glass is defined herein as optically isotropic             and (3) sapric. Because of the importance of fiber content in the
translucent glass or pumice of any color. It includes glass,            definitions of these materials, fibers are defined before the kinds
pumice, glass-coated crystalline minerals, glass aggregates, and        of organic soil materials.
glassy materials.
    Volcanic glass is typically a dominant component in
                                                                        Fibers
relatively unweathered tephra. Weathering and mineral
transformation of volcanic glass can produce short-range-order             Fibers are pieces of plant tissue in organic soil materials
minerals, such as allophane, imogolite, and ferrihydrite.               (excluding live roots) that:
    Volcanic glass content is the percent (by grain count) of
                                                                        1. Are large enough to be retained on a 100-mesh sieve
glass, glass-coated mineral grains, glass aggregates, and glassy
                                                                        (openings 0.15 mm across) when the materials are screened;
materials in the 0.02 to 2.0 mm fraction. Typically, the content
                                                                        and
is determined for one particle-size fraction (i.e., coarse silt, very
fine sand, or fine sand) and used as an estimate of glass content       2. Show evidence of the cellular structure of the plants from
in the 0.02 to 2.0 mm fraction.                                         which they are derived; and
    Volcanic glass content is a criterion in classification of andic
                                                                        3. Either are 2 cm or less in their smallest dimension or
soil properties, subgroups with the formative element “vitr(i),”
                                                                        are decomposed enough to be crushed and shredded with the
families with “ashy” substitutes for particle-size class, and the
                                                                        fingers.
glassy mineralogy class.
                                                                           Pieces of wood that are larger than 2 cm in cross section and
Weatherable Minerals                                                    are so undecomposed that they cannot be crushed and shredded
                                                                        with the fingers, such as large branches, logs, and stumps,
   Several references are made to weatherable minerals in this          are not considered fibers but are considered coarse fragments
taxonomy. Obviously, the stability of a mineral in a soil is a          (comparable to gravel, stones, and boulders in mineral soils).
partial function of the soil moisture regime. Where weatherable
minerals are referred to in the definitions of diagnostic horizons
                                                                        Fibric Soil Materials
and of various taxa in this taxonomy, a humid climate, either
present or past, is always assumed. Examples of the minerals               Fibric soil materials are organic soil materials that either:
that are included in the meaning of weatherable minerals are all
                                                                        1. Contain three-fourths or more (by volume) fibers after
2:1 phyllosilicates, chlorite, sepiolite, palygorskite, allophane,
                                                                        rubbing, excluding coarse fragments; or
1:1 trioctahedral phyllosilicates (serpentines), feldspars,
feldspathoids, ferromagnesian minerals, volcanic glass, zeolites,       2. Contain two-fifths or more (by volume) fibers after rubbing,
dolomite, and apatite in the 0.02 to 2.0 mm fraction.                   excluding coarse fragments, and yield color values and chromas
22                                                                                                                     Keys to Soil Taxonomy



of 7/1, 7/2, 8/1, 8/2, or 8/3 (fig. 2) on white chromatographic           and the lowest water content on a dry-weight basis at saturation.
or filter paper that is inserted into a paste made of the soil            Sapric soil materials are commonly very dark gray to black.
materials in a saturated sodium-pyrophosphate solution.                   They are relatively stable; i.e., they change very little physically
                                                                          and chemically with time in comparison to other organic soil
Hemic Soil Materials                                                      materials.
                                                                             Sapric materials have the following characteristics:
   Hemic soil materials (Gr. hemi, half; implying intermediate
decomposition) are intermediate in their degree of                        1. The fiber content, after rubbing, is less than one-sixth (by
decomposition between the less decomposed fibric and more                 volume), excluding coarse fragments; and
decomposed sapric materials. Their morphological features give            2. The color of the sodium-pyrophosphate extract on white
intermediate values for fiber content, bulk density, and water            chromatographic or filter paper is below or to the right of a
content. Hemic soil materials are partly altered both physically          line drawn to exclude blocks 5/1, 6/2, and 7/3 (fig. 2). If few
and biochemically.                                                        or no fibers can be detected and the color of the pyrophosphate
                                                                          extract is to the left of or above this line, the possibility that the
Sapric Soil Materials                                                     material is limnic must be considered.
   Sapric soil materials (Gr. sapros, rotten) are the most highly
decomposed of the three kinds of organic soil materials. They             Humilluvic Material
have the smallest amount of plant fiber, the highest bulk density,           Humilluvic material, i.e., illuvial humus, accumulates in the
                                                                          lower parts of some organic soils that are acid and have been
                                                                          drained and cultivated. The humilluvic material has a C14 age
                                                                          that is not older than the overlying organic materials. It has very
                                                                          high solubility in sodium pyrophosphate and rewets very slowly
                                                                          after drying. Most commonly, it accumulates near a contact with
                                                                          a sandy mineral horizon.
                                                                             To be recognized as a differentia in classification, the
                                                                          humilluvic material must constitute one-half or more (by
                                                                          volume) of a layer 2 cm or more thick.

                                                                          Limnic Materials
                                                                             The presence or absence of limnic deposits is taken into
                                                                          account in the higher categories of Histosols but not Histels.
                                                                          The nature of such deposits is considered in the lower categories
                                                                          of Histosols. Limnic materials include both organic and
                                                                          inorganic materials that were either (1) deposited in water
                                                                          by precipitation or through the action of aquatic organisms,
                                                                          such as algae or diatoms, or (2) derived from underwater and
                                                                          floating aquatic plants and subsequently modified by aquatic
                                                                          animals. They include coprogenous earth (sedimentary peat),
                                                                          diatomaceous earth, and marl.

                                                                          Coprogenous Earth
                                                                             A layer of coprogenous earth (sedimentary peat) is a limnic
                                                                          layer that:
                                                                          1. Contains many fecal pellets with diameters between a few
                                                                          hundredths and a few tenths of a millimeter; and
                                                                          2.   Has a color value, moist, of 4 or less; and
                                                                          3. Either forms a slightly viscous water suspension and is
                                                                          nonplastic or slightly plastic but not sticky, or shrinks upon
                                                                          drying, forming clods that are difficult to rewet and often tend to
                                                                          crack along horizontal planes; and
     Figure 2.—Value and chroma of pyrophosphate solution of fibric and
          sapric materials.                                               4.   Either yields a saturated sodium-pyrophosphate extract
Horizons and Characteristics Diagnostic for the Higher Categories                                                                      23



on white chromatographic or filter paper that has a color value      substratum shallower than those limits does not change the
of 7 or more and chroma of 2 or less (fig. 2) or has a cation-       lower boundary of the control section.
exchange capacity of less than 240 cmol(+) per kg organic               The control section of Histosols and Histels is divided
matter (measured by loss on ignition), or both.                      somewhat arbitrarily into three tiers—surface, subsurface, and
                                                                     bottom tiers.                                                           D
Diatomaceous Earth                                                                                                                           I
                                                                                                                                             A
     A layer of diatomaceous earth is a limnic layer that:           Surface Tier
1. If not previously dried, has a matrix color value of 3, 4,            The surface tier of a Histosol or Histel extends from the soil
or 5, which changes irreversibly on drying as a result of the        surface to a depth of 60 cm if either (1) the materials within that
irreversible shrinkage of organic-matter coatings on diatoms         depth are fibric and three-fourths or more of the fiber volume
(identifiable by microscopic, 440 X, examination of dry              is derived from Sphagnum or other mosses or (2) the materials
samples); and                                                        have a bulk density of less than 0.1. Otherwise, the surface tier
                                                                     extends from the soil surface to a depth of 30 cm.
2. Either yields a saturated sodium-pyrophosphate extract
                                                                         Some organic soils have a mineral surface layer less than 40
on white chromatographic or filter paper that has a color value
                                                                     cm thick as a result of flooding, volcanic eruptions, additions of
of 8 or more and chroma of 2 or less or has a cation-exchange
                                                                     mineral materials to increase soil strength or reduce the hazard
capacity of less than 240 cmol(+) per kg organic matter
                                                                     of frost, or other causes. If such a mineral layer is less than 30
(measured by loss on ignition), or both.
                                                                     cm thick, it constitutes the upper part of the surface tier; if it is
Marl                                                                 30 to 40 cm thick, it constitutes the whole surface tier and part
                                                                     of the subsurface tier.
     A layer of marl is a limnic layer that:
1.    Has a color value, moist, of 5 or more; and                    Subsurface Tier
2.    Reacts with dilute HCl to evolve CO2.                             The subsurface tier is normally 60 cm thick. If the control
                                                                     section ends at a shallower depth (at a densic, lithic, or
   The color of marl usually does not change irreversibly on
                                                                     paralithic contact or a water layer or in permafrost), however,
drying because a layer of marl contains too little organic matter,
                                                                     the subsurface tier extends from the lower boundary of the
even before it has been shrunk by drying, to coat the carbonate
                                                                     surface tier to the lower boundary of the control section. It
particles.
                                                                     includes any unconsolidated mineral layers that may be present
                                                                     within those depths.
Thickness of Organic Soil Materials
  (Control Section of Histosols and                                  Bottom Tier
  Histels)                                                               The bottom tier is 40 cm thick unless the control section has
   The thickness of organic materials over limnic materials,         its lower boundary at a shallower depth (at a densic, lithic, or
mineral materials, water, or permafrost is used to define the        paralithic contact or a water layer or in permafrost).
Histosols and Histels.                                                   Thus, if the organic materials are thick, there are two
   For practical reasons, an arbitrary control section has been      possible thicknesses of the control section, depending on the
established for the classification of Histosols and Histels.         presence or absence and the thickness of a surface mantle of
Depending on the kinds of soil material in the surface layers,       fibric moss or other organic material that has a low bulk density
the control section has a thickness of either 130 cm or 160 cm       (less than 0.1). If the fibric moss extends to a depth of 60 cm
from the soil surface if there is no densic, lithic, or paralithic   and is the dominant material within this depth (three-fourths
contact, thick layer of water, or permafrost within the respective   or more of the volume), the control section is 160 cm thick. If
limit. The thicker control section is used if the surface layers     the fibric moss is thin or absent, the control section extends to a
to a depth of 60 cm either contain three-fourths or more fibers      depth of 130 cm.
derived from Sphagnum, Hypnum, or other mosses or have a
bulk density of less than 0.1. Layers of water, which may be
between a few centimeters and many meters thick in these
                                                                     Horizons and Characteristics
soils, are considered to be the lower boundary of the control          Diagnostic for Both Mineral and
section only if the water extends below a depth of 130 or
160 cm, respectively. A densic, lithic, or paralithic contact, if
                                                                       Organic Soils
shallower than 130 or 160 cm, constitutes the lower boundary of         Following are descriptions of the horizons and characteristics
the control section. In some soils the lower boundary is 25 cm       that are diagnostic for both mineral and organic soils.
below the upper limit of permafrost. An unconsolidated mineral
24                                                                                                                  Keys to Soil Taxonomy




Aquic Conditions                                                           c. Anthric saturation.—This term refers to a special kind
                                                                           of aquic conditions that occurs in soils that are cultivated and
   Soils with aquic (L. aqua, water) conditions are those                  irrigated (flood irrigation). Soils with anthraquic conditions
that currently undergo continuous or periodic saturation and               must meet the requirements for aquic conditions and in
reduction. The presence of these conditions is indicated by                addition have both of the following:
redoximorphic features, except in Histosols and Histels, and
can be verified by measuring saturation and reduction, except                 (1) A tilled surface layer and a directly underlying
in artificially drained soils. Artificial drainage is defined here as         slowly permeable layer that has, for 3 months or more in
the removal of free water from soils having aquic conditions by               normal years, both:
surface mounding, ditches, or subsurface tiles or the prevention                 (a)   Saturation and reduction; and
of surface or ground water from reaching the soils by dams,
levees, surface pumps, or other means. In these soils water                      (b)   Chroma of 2 or less in the matrix; and
table levels and/or their duration are changed significantly in               (2) A subsurface horizon with one or more of the
connection with specific types of land use. Upon removal of the               following:
drainage practices, aquic conditions would return. In the keys,
artificially drained soils are included with soils that have aquic               (a) Redox depletions with a color value, moist, of 4
conditions.                                                                      or more and chroma of 2 or less in macropores; or
   Elements of aquic conditions are as follows:                                  (b)   Redox concentrations of iron; or
1. Saturation is characterized by zero or positive pressure in                   (c) 2 times or more the amount of iron (by dithionite
the soil water and can generally be determined by observing                      citrate) contained in the tilled surface layer.
free water in an unlined auger hole. Problems may arise,
however, in clayey soils with peds, where an unlined auger              2. The degree of reduction in a soil can be characterized by the
hole may fill with water flowing along faces of peds while the          direct measurement of redox potentials. Direct measurements
soil matrix is and remains unsaturated (bypass flow). Such free         should take into account chemical equilibria as expressed by
water may incorrectly suggest the presence of a water table,            stability diagrams in standard soil textbooks. Reduction and
while the actual water table occurs at greater depth. Use of well       oxidation processes are also a function of soil pH. Obtaining
sealed piezometers or tensiometers is therefore recommended             accurate measurements of the degree of reduction in a soil is
for measuring saturation. Problems may still occur, however,            difficult. In the context of this taxonomy, however, only a degree
if water runs into piezometer slits near the bottom of the              of reduction that results in reduced iron is considered, because it
piezometer hole or if tensiometers with slowly reacting                 produces the visible redoximorphic features that are identified in
manometers are used. The first problem can be overcome by               the keys. A simple field test is available to determine if reduced
using piezometers with smaller slits and the second by using            iron ions are present. A freshly broken surface of a field-wet
transducer tensiometry, which reacts faster than manometers.            soil sample is treated with alpha,alpha-dipyridyl in neutral,
Soils are considered wet if they have pressure heads greater            1N ammonium-acetate solution. The appearance of a strong
than -1 kPa. Only macropores, such as cracks between peds               red color on the freshly broken surface indicates the presence
or channels, are then filled with air, while the soil matrix is         of reduced iron ions. A positive reaction to the alpha,alpha-
usually still saturated. Obviously, exact measurements of the wet       dipyridyl field test for ferrous iron (Childs, 1981) may be
state can be obtained only with tensiometers. For operational           used to confirm the existence of reducing conditions and is
purposes, the use of piezometers is recommended as a standard           especially useful in situations where, despite saturation, normal
method.                                                                 morphological indicators of such conditions are either absent
   The duration of saturation required for creating aquic               or obscured (as by the dark colors characteristic of melanic
conditions varies, depending on the soil environment, and is not        great groups). A negative reaction, however, does not imply that
specified.                                                              reducing conditions are always absent. It may only mean that the
   Three types of saturation are defined:                               level of free iron in the soil is below the sensitivity limit of the
                                                                        test or that the soil is in an oxidized phase at the time of testing.
     a. Endosaturation.—The soil is saturated with water in all         Use of alpha,alpha-dipyridyl in a 10 percent acetic-acid solution
     layers from the upper boundary of saturation to a depth of         is not recommended because the acid is likely to change soil
     200 cm or more from the mineral soil surface.                      conditions, for example, by dissolving CaCO3.
                                                                            The duration of reduction required for creating aquic
     b. Episaturation.—The soil is saturated with water in one
                                                                        conditions is not specified.
     or more layers within 200 cm of the mineral soil surface
     and also has one or more unsaturated layers, with an upper         3. Redoximorphic features associated with wetness result
     boundary above a depth of 200 cm, below the saturated layer.       from alternating periods of reduction and oxidation of iron and
     The zone of saturation, i.e., the water table, is perched on top   manganese compounds in the soil. Reduction occurs during
     of a relatively impermeable layer.                                 saturation with water, and oxidation occurs when the soil is not
Horizons and Characteristics Diagnostic for the Higher Categories                                                                    25



saturated. The reduced iron and manganese ions are mobile              Field experience indicates that it is not possible to define
and may be transported by water as it moves through the soil.       a specific set of redoximorphic features that is uniquely
Certain redox patterns occur as a function of the patterns in       characteristic of all of the taxa in one particular category.
which the ion-carrying water moves through the soil and as          Therefore, color patterns that are unique to specific taxa are
a function of the location of aerated zones in the soil. Redox      referenced in the keys.                                               D
                                                                                                                                          I
patterns are also affected by the fact that manganese is reduced       Anthraquic conditions are a variant of episaturation and are       A
more rapidly than iron, while iron oxidizes more rapidly upon       associated with controlled flooding (for such crops as wetland
aeration. Characteristic color patterns are created by these        rice and cranberries), which causes reduction processes in the
processes. The reduced iron and manganese ions may be               saturated, puddled surface soil and oxidation of reduced and
removed from a soil if vertical or lateral fluxes of water occur,   mobilized iron and manganese in the unsaturated subsoil.
in which case there is no iron or manganese precipitation in
that soil. Wherever the iron and manganese are oxidized and         Cryoturbation
precipitated, they form either soft masses or hard concretions or
nodules. Movement of iron and manganese as a result of redox           Cryoturbation (frost churning) is the mixing of the soil
processes in a soil may result in redoximorphic features that are   matrix within the pedon that results in irregular or broken
defined as follows:                                                 horizons, involutions, accumulation of organic matter on the
                                                                    permafrost table, oriented rock fragments, and silt caps on rock
   a. Redox concentrations.—These are zones of apparent             fragments.
   accumulation of Fe-Mn oxides, including:
      (1) Nodules and concretions, which are cemented               Densic Contact
      bodies that can be removed from the soil intact.                 A densic contact (L. densus, thick) is a contact between soil
      Concretions are distinguished from nodules on the             and densic materials (defined below). It has no cracks, or the
      basis of internal organization. A concretion typically        spacing of cracks that roots can enter is 10 cm or more.
      has concentric layers that are visible to the naked eye.
      Nodules do not have visible organized internal structure.     Densic Materials
      Boundaries commonly are diffuse if formed in situ and
      sharp after pedoturbation. Sharp boundaries may be relict        Densic materials are relatively unaltered materials (do
      features in some soils; and                                   not meet the requirements for any other named diagnostic
                                                                    horizons or any other diagnostic soil characteristic) that have
      (2) Masses, which are noncemented concentrations of           a noncemented rupture-resistance class. The bulk density
      substances within the soil matrix; and                        or the organization is such that roots cannot enter, except in
      (3) Pore linings, i.e., zones of accumulation along           cracks. These are mostly earthy materials, such as till, volcanic
      pores that may be either coatings on pore surfaces or         mudflows, and some mechanically compacted materials, for
      impregnations from the matrix adjacent to the pores.          example, mine spoils. Some noncemented rocks can be densic
                                                                    materials if they are dense or resistant enough to keep roots
   b. Redox depletions.—These are zones of low chroma               from entering, except in cracks.
   (chromas less than those in the matrix) where either Fe-            Densic materials are noncemented and thus differ from
   Mn oxides alone or both Fe-Mn oxides and clay have been          paralithic materials and the material below a lithic contact, both
   stripped out, including:                                         of which are cemented.
      (1) Iron depletions, i.e., zones that contain low amounts        Densic materials have, at their upper boundary, a densic
      of Fe and Mn oxides but have a clay content similar to        contact if they have no cracks or if the spacing of cracks that
      that of the adjacent matrix (often referred to as albans or   roots can enter is 10 cm or more. These materials can be used
      neoalbans); and                                               to differentiate soil series if the materials are within the series
                                                                    control section.
      (2) Clay depletions, i.e., zones that contain low amounts
      of Fe, Mn, and clay (often referred to as silt coatings or
                                                                    Gelic Materials
      skeletans).
                                                                        Gelic materials are mineral or organic soil materials that
   c. Reduced matrix.—This is a soil matrix that has low
                                                                    show evidence of cryoturbation (frost churning) and/or ice
   chroma in situ but undergoes a change in hue or chroma
                                                                    segregation in the active layer (seasonal thaw layer) and/or the
   within 30 minutes after the soil material has been exposed to
                                                                    upper part of the permafrost. Cryoturbation is manifested by
   air.
                                                                    irregular and broken horizons, involutions, accumulation of
   d. In soils that have no visible redoximorphic features, a       organic matter on top of and within the permafrost, oriented
   reaction to an alpha,alpha-dipyridyl solution satisfies the      rock fragments, and silt-enriched layers. The characteristic
   requirement for redoximorphic features.                          structures associated with gelic materials include platy, blocky,
26                                                                                                               Keys to Soil Taxonomy



or granular macrostructures; the structural results of sorting;      they have no cracks or if the spacing of cracks that roots can
and orbiculic, conglomeric, banded, or vesicular microfabrics.       enter is 10 cm or more. Commonly, these materials are partially
Ice segregation is manifested by ice lenses, vein ice, segregated    weathered bedrock or weakly consolidated bedrock, such as
ice crystals, and ice wedges. Cryopedogenic processes that lead      sandstone, siltstone, or shale. Paralithic materials can be used
to gelic materials are driven by the physical volume change of       to differentiate soil series if the materials are within the series
water to ice, moisture migration along a thermal gradient in the     control section. Fragments of paralithic materials 2.0 mm or
frozen system, or thermal contraction of the frozen material by      more in diameter are referred to as pararock fragments.
continued rapid cooling.
                                                                     Permafrost
Glacic Layer                                                             Permafrost is defined as a thermal condition in which a
   A glacic layer is massive ice or ground ice in the form of ice    material (including soil material) remains below 0 oC for 2
lenses or wedges. The layer is 30 cm or more thick and contains      or more years in succession. Those gelic materials having
75 percent or more visible ice.                                      permafrost contain the unfrozen soil solution that drives
                                                                     cryopedogenic processes. Permafrost may be cemented by ice
Lithic Contact                                                       or, in the case of insufficient interstitial water, may be dry. The
                                                                     frozen layer has a variety of ice lenses, vein ice, segregated ice
    A lithic contact is the boundary between soil and a coherent     crystals, and ice wedges. The permafrost table is in dynamic
underlying material. Except in Ruptic-Lithic subgroups, the          equilibrium with the environment.
underlying material must be virtually continuous within the
limits of a pedon. Cracks that can be penetrated by roots
                                                                     Soil Moisture Regimes
are few, and their horizontal spacing is 10 cm or more. The
underlying material must be sufficiently coherent when moist             The term “soil moisture regime” refers to the presence or
to make hand-digging with a spade impractical, although the          absence either of ground water or of water held at a tension
material may be chipped or scraped with a spade. The material        of less than 1500 kPa in the soil or in specific horizons during
below a lithic contact must be in a strongly cemented or more        periods of the year. Water held at a tension of 1500 kPa or
cemented rupture-resistance class. Commonly, the material            more is not available to keep most mesophytic plants alive. The
is indurated. The underlying material considered here does           availability of water is also affected by dissolved salts. If a soil
not include diagnostic soil horizons, such as a duripan or a         is saturated with water that is too salty to be available to most
petrocalcic horizon.                                                 plants, it is considered salty rather than dry. Consequently, a
    A lithic contact is diagnostic at the subgroup level if it is    horizon is considered dry when the moisture tension is 1500
within 125 cm of the mineral soil surface in Oxisols and within      kPa or more and is considered moist if water is held at a
50 cm of the mineral soil surface in all other mineral soils. In     tension of less than 1500 kPa but more than zero. A soil may
Gelisols composed mainly of organic soil materials, the lithic       be continuously moist in some or all horizons either throughout
contact is diagnostic at the subgroup level if it is within 50       the year or for some part of the year. It may be either moist
cm of the soil surface in Folistels or within 100 cm of the soil     in winter and dry in summer or the reverse. In the Northern
surface in Fibristels, Hemistels, and Sapristels. In Histosols       Hemisphere, summer refers to June, July, and August and winter
the lithic contact must be at the lower boundary of the control      refers to December, January, and February.
section to be recognized at the subgroup level.
                                                                     Normal Years

Paralithic Contact                                                      In the discussions that follow and throughout the keys, the
                                                                     term “normal years” is used. A normal year is defined as a year
   A paralithic (lithic-like) contact is a contact between soil      that has:
and paralithic materials (defined below) where the paralithic
materials have no cracks or the spacing of cracks that roots can     1. Annual precipitation that is plus or minus one standard
enter is 10 cm or more.                                              deviation of the long-term (30 years or more) mean annual
                                                                     precipitation; and
Paralithic Materials                                                 2. Mean monthly precipitation that is plus or minus one
                                                                     standard deviation of the long-term monthly precipitation for 8
   Paralithic materials are relatively unaltered materials (do
                                                                     of the 12 months.
not meet the requirements for any other named diagnostic
horizons or any other diagnostic soil characteristic) that have an      For the most part, normal years can be calculated from the
extremely weakly cemented to moderately cemented rupture-            mean annual precipitation; however, when catastrophic events
resistance class. Cementation, bulk density, and the organization    occur during a year, the standard deviations of the monthly
are such that roots cannot enter, except in cracks. Paralithic       means should also be calculated. The term “normal years”
materials have, at their upper boundary, a paralithic contact if     replaces the terms “most years” and “6 out of 10 years,” which
Horizons and Characteristics Diagnostic for the Higher Categories                                                                         27



were used in the 1975 edition of Soil Taxonomy (USDA, SCS,              moisture is not being increased by irrigation or fallowing. These
1975). When precipitation data are evaluated to determine if the        cultural practices affect the soil moisture conditions as long as
criterion for the presence of aquic conditions, or number of days       they are continued.
that the moisture control section is moist, or number of days that          Aquic soil moisture regime.—The aquic (L. aqua, water)
some part of the soil is saturated has been met, it is permissible      soil moisture regime is a reducing regime in a soil that is             D
                                                                                                                                                I
to include data from periods with below normal rainfall.                virtually free of dissolved oxygen because it is saturated by           A
Similarly, when precipitation data are evaluated to determine           water. Some soils are saturated with water at times while
if the criterion for the number of days that the moisture control       dissolved oxygen is present, either because the water is moving
section is dry has been met, it is permissible to include data          or because the environment is unfavorable for micro-organisms
from periods with above normal rainfall. It is assumed that if          (e.g., if the temperature is less than 1 oC); such a regime is not
the criteria are met during these periods, they will also be met        considered aquic.
during normal years.                                                        It is not known how long a soil must be saturated before it
                                                                        is said to have an aquic soil moisture regime, but the duration
Soil Moisture Control Section
                                                                        must be at least a few days, because it is implicit in the concept
   The intent in defining the soil moisture control section is to       that dissolved oxygen is virtually absent. Because dissolved
facilitate estimation of soil moisture regimes from climatic data.      oxygen is removed from ground water by respiration of micro-
The upper boundary of this control section is the depth to which        organisms, roots, and soil fauna, it is also implicit in the concept
a dry (tension of more than 1500 kPa, but not air-dry) soil will        that the soil temperature is above biologic zero for some time
be moistened by 2.5 cm of water within 24 hours. The lower              while the soil is saturated. Biologic zero is defined as 5 oC in
boundary is the depth to which a dry soil will be moistened by          this taxonomy. In some of the very cold regions of the world,
7.5 cm of water within 48 hours. These depths do not include            however, biological activity occurs at temperatures below 5 oC.
the depth of moistening along any cracks or animal burrows that             Very commonly, the level of ground water fluctuates with
are open to the surface.                                                the seasons; it is highest in the rainy season or in fall, winter, or
   If 7.5 cm of water moistens the soil to a densic, lithic,            spring if cold weather virtually stops evapotranspiration. There
paralithic, or petroferric contact or to a petrocalcic or               are soils, however, in which the ground water is always at or
petrogypsic horizon or a duripan, the contact or the upper              very close to the surface. Examples are soils in tidal marshes
boundary of the cemented horizon constitutes the lower                  or in closed, landlocked depressions fed by perennial streams.
boundary of the soil moisture control section. If a soil is             Such soils are considered to have a peraquic soil moisture
moistened to one of these contacts or horizons by 2.5 cm of             regime.
water, the soil moisture control section is the boundary of the             Aridic and torric (L. aridus, dry, and L. torridus, hot
contact itself. The control section of such a soil is considered        and dry) soil moisture regimes.—These terms are used for
moist if the contact or upper boundary of the cemented horizon          the same moisture regime but in different categories of the
has a thin film of water. If that upper boundary is dry, the            taxonomy.
control section is considered dry.                                          In the aridic (torric) soil moisture regime, the moisture
   The moisture control section of a soil extends approximately         control section is, in normal years:
(1) from 10 to 30 cm below the soil surface if the particle-size
class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey;   1. Dry in all parts for more than half of the cumulative days
(2) from 20 to 60 cm if the particle-size class is coarse-loamy;        per year when the soil temperature at a depth of 50 cm below
and (3) from 30 to 90 cm if the particle-size class is sandy. If        the soil surface is above 5 oC; and
the soil contains rock and pararock fragments that do not absorb        2. Moist in some or all parts for less than 90 consecutive days
and release water, the limits of the moisture control section           when the soil temperature at a depth of 50 cm below the soil
are deeper. The limits of the soil moisture control section             surface is above 8 oC.
are affected not only by the particle-size class but also by
differences in soil structure or pore-size distribution or by other         Soils that have an aridic (torric) soil moisture regime
factors that influence the movement and retention of water in           normally occur in areas of arid climates. A few are in areas of
the soil.                                                               semiarid climates and either have physical properties that keep
                                                                        them dry, such as a crusty surface that virtually precludes the
Classes of Soil Moisture Regimes
                                                                        infiltration of water, or are on steep slopes where runoff is high.
   The soil moisture regimes are defined in terms of the level of       There is little or no leaching in this soil moisture regime, and
ground water and in terms of the seasonal presence or absence           soluble salts accumulate in the soils if there is a source.
of water held at a tension of less than 1500 kPa in the moisture            The limits set for soil temperature exclude from these soil
control section. It is assumed in the definitions that the soil         moisture regimes soils in the very cold and dry polar regions
supports whatever vegetation it is capable of supporting, i.e.,         and in areas at high elevations. Such soils are considered to have
crops, grass, or native vegetation, and that the amount of stored       anhydrous conditions (defined earlier).
28                                                                                                               Keys to Soil Taxonomy



    Udic soil moisture regime.—The udic (L. udus, humid)              control section is dry in all parts for less than 45 consecutive
soil moisture regime is one in which the soil moisture control        days in the 4 months following the summer solstice.
section is not dry in any part for as long as 90 cumulative               In tropical and subtropical regions that have a monsoon
days in normal years. If the mean annual soil temperature is          climate with either one or two dry seasons, summer and winter
lower than 22 oC and if the mean winter and mean summer soil          seasons have little meaning. In those regions the soil moisture
temperatures at a depth of 50 cm below the soil surface differ        regime is ustic if there is at least one rainy season of 3 months
by 6 oC or more, the soil moisture control section, in normal         or more. In temperate regions of subhumid or semiarid climates,
years, is dry in all parts for less than 45 consecutive days in the   the rainy seasons are usually spring and summer or spring and
4 months following the summer solstice. In addition, the udic         fall, but never winter. Native plants are mostly annuals or plants
soil moisture regime requires, except for short periods, a three-     that have a dormant period while the soil is dry.
phase system, solid-liquid-gas, in part or all of the soil moisture       Xeric soil moisture regime.—The xeric (Gr. xeros, dry)
control section when the soil temperature is above 5 oC.              soil moisture regime is the typical moisture regime in areas of
    The udic soil moisture regime is common to the soils of           Mediterranean climates, where winters are moist and cool and
humid climates that have well distributed rainfall; have enough       summers are warm and dry. The moisture, which falls during
rain in summer so that the amount of stored moisture plus             the winter, when potential evapotranspiration is at a minimum,
rainfall is approximately equal to, or exceeds, the amount of         is particularly effective for leaching. In areas of a xeric soil
evapotranspiration; or have adequate winter rains to recharge the     moisture regime, the soil moisture control section, in normal
soils and cool, foggy summers, as in coastal areas. Water moves       years, is dry in all parts for 45 or more consecutive days in the
downward through the soils at some time in normal years.              4 months following the summer solstice and moist in all parts
    In climates where precipitation exceeds evapotranspiration in     for 45 or more consecutive days in the 4 months following
all months of normal years, the moisture tension rarely reaches       the winter solstice. Also, in normal years, the moisture
100 kPa in the soil moisture control section, although there are      control section is moist in some part for more than half of the
occasional brief periods when some stored moisture is used. The       cumulative days per year when the soil temperature at a depth
water moves through the soil in all months when it is not frozen.     of 50 cm below the soil surface is higher than 5 oC or for 90 or
Such an extremely wet soil moisture regime is called perudic (L.      more consecutive days when the soil temperature at a depth of
per, throughout in time, and L. udus, humid). In the names of         50 cm is higher than 8 oC. The mean annual soil temperature is
most taxa, the formative element “ud” is used to indicate either      lower than 22 oC, and the mean summer and mean winter soil
a udic or a perudic regime; the formative element “per” is used       temperatures differ by 6 oC or more either at a depth of 50 cm
in selected taxa.                                                     below the soil surface or at a densic, lithic, or paralithic contact
    Ustic soil moisture regime.—The ustic (L. ustus, burnt;           if shallower.
implying dryness) soil moisture regime is intermediate between
the aridic regime and the udic regime. Its concept is one of          Soil Temperature Regimes
moisture that is limited but is present at a time when conditions
                                                                      Classes of Soil Temperature Regimes
are suitable for plant growth. The concept of the ustic soil
moisture regime is not applied to soils that have permafrost             Following is a description of the soil temperature regimes
(defined above).                                                      used in defining classes at various categorical levels in this
    If the mean annual soil temperature is 22 oC or higher or if      taxonomy.
the mean summer and winter soil temperatures differ by less              Gelic (L. gelare, to freeze).— Soils in this temperature
than 6 oC at a depth of 50 cm below the soil surface, the soil        regime have a mean annual soil temperature at or below 0 oC
moisture control section in areas of the ustic soil moisture          (in Gelic suborders and Gelic great groups) or 1 oC or lower (in
regime is dry in some or all parts for 90 or more cumulative          Gelisols) either at a depth of 50 cm below the soil surface or at a
days in normal years. It is moist, however, in some part either       densic, lithic, or paralithic contact, whichever is shallower.
for more than 180 cumulative days per year or for 90 or more             Cryic (Gr. kryos, coldness; meaning very cold
consecutive days.                                                     soils).—Soils in this temperature regime have a mean annual
    If the mean annual soil temperature is lower than 22 oC and       temperature between 0 and 8 oC but do not have permafrost.
if the mean summer and winter soil temperatures differ by
                                                                      1. In mineral soils the mean summer soil temperature (June,
6 oC or more at a depth of 50 cm below the soil surface, the
                                                                      July, and August in the Northern Hemisphere and December,
soil moisture control section in areas of the ustic soil moisture
                                                                      January, and February in the Southern Hemisphere) either at a
regime is dry in some or all parts for 90 or more cumulative
                                                                      depth of 50 cm below the soil surface or at a densic, lithic, or
days in normal years, but it is not dry in all parts for more than
                                                                      paralithic contact, whichever is shallower, is as follows:
half of the cumulative days when the soil temperature at a depth
of 50 cm is higher than 5 oC. If in normal years the moisture            a. If the soil is not saturated with water during some part of
control section is moist in all parts for 45 or more consecutive         the summer and
days in the 4 months following the winter solstice, the moisture
Horizons and Characteristics Diagnostic for the Higher Categories                                                                      29



      (1)   If there is no O horizon: between 0 and 15 oC; or        Sulfidic Materials
      (2)   If there is an O horizon: between 0 and 8 C; or
                                                      o
                                                                         Sulfidic materials contain oxidizable sulfur compounds
   b. If the soil is saturated with water during some part of the    (elemental S or most commonly sulfide minerals, such as
   summer and                                                        pyrite or iron monosulfides). They are mineral or organic soil          D
                                                                     materials that have a pH value of more than 3.5 and that become         I
                                                                                                                                             A
      (1)   If there is no O horizon: between 0 and 13 oC; or        significantly more acid when oxidized. Sulfidic materials
      (2) If there is an O horizon or a histic epipedon: between     accumulate as a soil or sediment that is permanently saturated,
      0 and 6 oC.                                                    generally with brackish water. The sulfates in the water are
                                                                     biologically reduced to sulfides as the materials accumulate.
2. In organic soils the mean annual soil temperature is              Sulfidic materials most commonly accumulate in coastal
between 0 and 6 oC.                                                  marshes near the mouth of rivers that carry noncalcareous
    Cryic soils that have an aquic soil moisture regime              sediments, but they may occur in freshwater marshes if there
commonly are churned by frost.                                       is sulfur in the water. Upland sulfidic materials may have
    Isofrigid soils could also have a cryic soil temperature         accumulated in a similar manner in the geologic past.
regime. A few with organic materials in the upper part are               If a soil containing sulfidic materials is drained or if sulfidic
exceptions.                                                          materials are otherwise exposed to aerobic conditions, the
    The concepts of the soil temperature regimes described           sulfides oxidize and form sulfuric acid. The pH value, which
below are used in defining classes of soils in the low categories.   normally is near neutrality before drainage or exposure, may
    Frigid.—A soil with a frigid soil temperature regime is          drop below 3. The acid may induce the formation of iron
warmer in summer than a soil with a cryic regime, but its            and aluminum sulfates. The iron hydroxysulfate mineral
mean annual temperature is between 0 and 8 oC and the                jarosite may segregate, forming the yellow redoximorphic
difference between mean summer (June, July, and August)              concentrations that commonly characterize a sulfuric horizon.
and mean winter (December, January, and February) soil               The transition from sulfidic materials to a sulfuric horizon
temperatures is 6 oC or more either at a depth of 50 cm below        normally requires only a few months and may occur within a
the soil surface or at a densic, lithic, or paralithic contact,      few weeks. A sample of sulfidic materials, if air-dried slowly
whichever is shallower.                                              in shade for about 2 months with occasional remoistening,
    Mesic.—The mean annual soil temperature is 8 oC or higher        becomes extremely acid.
but lower than 15 oC, and the difference between mean summer         Required Characteristics
and mean winter soil temperatures is 6 oC or more either at a
depth of 50 cm below the soil surface or at a densic, lithic, or        Sulfidic materials have one or both of the following:
paralithic contact, whichever is shallower.                          1. A pH value (1:1 in water) of more than 3.5, and, when the
    Thermic.—The mean annual soil temperature is 15 oC or            materials are incubated at room temperature as a layer 1 cm
higher but lower than 22 oC, and the difference between mean         thick under moist aerobic conditions (repeatedly moistened and
summer and mean winter soil temperatures is 6 oC or more             dried on a weekly basis), the pH decreases by 0.5 or more units
either at a depth of 50 cm below the soil surface or at a densic,    to a value of 4.0 or less (1:1 by weight in water or in a minimum
lithic, or paralithic contact, whichever is shallower.               of water to permit measurement) within 16 weeks or longer
    Hyperthermic.—The mean annual soil temperature is                until the pH reaches a nearly constant value if the pH is still
22 oC or higher, and the difference between mean summer              dropping after 16 weeks; or
and mean winter soil temperatures is 6 oC or more either at a
depth of 50 cm below the soil surface or at a densic, lithic, or     2. A pH value (1:1 in water) of more than 3.5 and 0.75 percent
paralithic contact, whichever is shallower.                          or more S (dry mass), mostly in the form of sulfides, and less
    If the name of a soil temperature regime has the prefix iso,     than three times as much calcium carbonate equivalent as S.
the mean summer and mean winter soil temperatures differ
by less than 6 oC at a depth of 50 cm or at a densic, lithic, or
                                                                     Sulfuric Horizon
paralithic contact, whichever is shallower.
    Isofrigid.—The mean annual soil temperature is lower than           Brackish water sediments frequently contain pyrite or other
8 oC.                                                                iron sulfide minerals or rarely elemental sulfur, which form
    Isomesic.—The mean annual soil temperature is 8 oC or            sulfuric acid upon the oxidation of the sulfur forms they contain
higher but lower than 15 oC.                                         and/or upon the oxidation and hydrolysis of the iron in the
    Isothermic.—The mean annual soil temperature is 15 oC or         iron sulfides. Pyrite is an iron sulfide mineral that forms as a
higher but lower than 22 oC.                                         result of the microbial decomposition of organic matter under
    Isohyperthermic.—The mean annual soil temperature is             anaerobic conditions. Pyrite forms after iron oxide and sulfate
22 oC or higher.                                                     from sea water (or other sources) become reduced to ferrous
30



iron and sulfide, respectively, and then combine to form a very       1. The horizon has:
insoluble compound (see description of the sulfidization process         a. Concentrations of jarosite, schwertmannite, or other iron
given by Fanning and Fanning, 1989, or Fanning et al., 2002).            and/or aluminum sulfates or hydroxysulfate minerals; or
Characteristically, the pyrite crystals occur as nests or framboids
composed of bipyramidal crystals of pyrite. In an oxidizing              b. 0.05 percent or more water-soluble sulfate; or
environment, pyrite oxidizes and the products of oxidation            2. The layer directly underlying the horizon consists of sulfidic
(and the hydrolysis of the ferric iron produced) are iron oxides      materials (defined above).
(and under sufficiently acidic and oxidizing conditions, jarosite
and/or schwertmannite) and sulfuric acid. The jarosite has a
straw-yellow color and frequently lines pores in the soil. Jarosite   Literature Cited
concentrations are among the indicators of a sulfuric horizon,
                                                                         Brewer, R. 1976. Fabric and Mineral Analysis of Soils.
but jarosite is not present in all sulfuric horizons.
                                                                      Second edition. John Wiley and Sons, Inc. New York, New York.
   The low pH and high amount of soluble sulfates, and/or
                                                                         Burt, R., ed. 2004. Soil Survey Laboratory Methods Manual.
underlying sulfidic materials, are other indicators of a sulfuric
                                                                      Soil Survey Investigations Report 42, Version 4.0. United States
horizon. A quick test of sulfidic materials is a rapid fall in pH
                                                                      Department of Agriculture, Natural Resources Conservation
on drying or after treatment with an oxidizing agent, such as
                                                                      Service, National Soil Survey Center.
hydrogen peroxide.
                                                                         Childs, C.W. 1981. Field Test for Ferrous Iron and Ferric-
   A sulfuric horizon (L. sulfur) forms as a result of drainage
                                                                      Organic Complexes (on Exchange Sites or in Water-Soluble
(most commonly artificial drainage) and oxidation of sulfide-
                                                                      Forms) in Soils. Austr. J. of Soil Res. 19: 175-180.
rich mineral or organic soil materials. It can form in areas where
                                                                         Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology,
sulfidic materials have been exposed as a result of surface
                                                                      Genesis, and Classification. John Wiley and Sons, New York.
mining, dredging, or other earth-moving operations. A sulfuric
                                                                         Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R. Islam,
horizon is detrimental to most plants and, if sufficiently acid at
                                                                      and S.A. Tangren. 2002. Sulfides and Sulfates. In J.B. Dixon
the soil surface, may prevent plant growth or limit it to certain
                                                                      and D.G. Schulze (eds.), Soil Mineralogy with Environmental
plant species, such as Phragmites australis, that can tolerate the
                                                                      Applications, pp. 229-260. Soil Sci. Soc. Am., Madison, WI.
acidity under certain conditions.
                                                                         Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening and Soil
                                                                      Classification. Initial Soil Formation in Alluvial Deposits and a
Required Characteristics
                                                                      Classification of the Resulting Soils. Int. Inst. Land Reclam. and
    The sulfuric horizon is 15 cm or more thick and is composed       Impr. Pub. 13. Wageningen, The Netherlands.
of either mineral or organic soil material that has a pH value           United States Department of Agriculture, Soil Conservation
(1:1 by weight in water or in a minimum of water to permit            Service. 1975. Soil Taxonomy: A Basic System of Soil
measurement) of 3.5 or less or less than 4.0 if sulfide or other S-   Classification for Making and Interpreting Soil Surveys. Soil
bearing minerals that produce sulfuric acid upon their oxidation      Surv. Staff. U.S. Dep. Agric. Handb. 436.
are present. The horizon shows evidence that the low pH value            United States Department of Agriculture, Soil Conservation
is caused by sulfuric acid.                                           Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S.
    The evidence is one or both of the following:                     Dep. Agric. Handb. 18.
                                                                                                                                          31




CHAPTER 4

                                                    Identification of the Taxonomic Class of a Soil
                                                                                                                                                I
                                                                                                                                                D
                                                                                                                                                E
    The taxonomic class of a specific soil can be determined             not included in this text. Definitions of the series and of the
by using the keys that follow in this and other chapters. It             control section are given in chapter 17.
is assumed that the reader is familiar with the definitions of              In the “Key to Soil Orders” and the other keys that follow,
diagnostic horizons and properties that are given in chapters            the diagnostic horizons and the properties mentioned do not
2 and 3 of this publication and with the meanings of the terms           include those below any densic, lithic, paralithic, or petroferric
used for describing soils given in the Soil Survey Manual. The           contact. The properties of buried soils and the properties of a
Index at the back of this publication indicates the pages on             surface mantle are considered on the basis of whether or not
which definitions of terms are given.                                    the soil meets the meaning of the term “buried soil” given in
    Standard rounding conventions should be used to determine            chapter 1.
numerical values.                                                           If a soil has a surface mantle and is not a buried soil, the top
    Soil colors (hue, value, and chroma) are used in many of the         of the original surface layer is considered the “soil surface” for
criteria that follow. Soil colors typically change value and some        determining depth to and thickness of diagnostic horizons and
change hue and chroma, depending on the water state. In many             most other diagnostic soil characteristics. The only properties
of the criteria of the keys, the water state is specified. If no water   of the surface mantle that are considered are soil temperature,
state is specified, the soil is considered to meet the criterion if it   soil moisture (including aquic conditions), and any andic or
does so when moist or dry or both moist and dry.                         vitrandic properties and family criteria.
    All of the keys in this taxonomy are designed in such a way             If a soil profile includes a buried soil, the present soil
that the user can determine the correct classification of a soil         surface is used to determine soil moisture and temperature as
by going through the keys systematically. The user must start            well as depth to and thickness of diagnostic horizons and other
at the beginning of the “Key to Soil Orders” and eliminate, one          diagnostic soil characteristics. Diagnostic horizons of the buried
by one, all classes that include criteria that do not fit the soil in    soil are not considered in selecting taxa unless the criteria in the
question. The soil belongs to the first class listed for which it        keys specifically indicate buried horizons, such as in Thapto-
meets all the required criteria.                                         Histic subgroups. Most other diagnostic soil characteristics
    In classifying a specific soil, the user of soil taxonomy begins     of the buried soil are not considered, but organic carbon if of
by checking through the “Key to Soil Orders” to determine                Holocene age, andic soil properties, base saturation, and all
the name of the first order that, according to the criteria listed,      properties used to determine family and series placement are
includes the soil in question. The next step is to go to the page        considered.
indicated to find the “Key to Suborders” of that particular order.          If diagnostic horizons or characteristics are criteria that must
Then the user systematically goes through the key to identify            be “within” a specified depth measured from the soil surface,
the suborder that includes the soil, i.e., the first in the list for     then the upper boundary of the first subhorizon meeting the
which it meets all the required criteria. The same procedure is          requirements for the diagnostic horizon or characteristic must
used to find the great group class of the soil in the “Key to Great      be within the specified depth.
Groups” of the identified suborder. Likewise, going through the
“Key to Subgroups” of that great group, the user selects as the
                                                                         Key to Soil Orders
correct subgroup name the name of the first taxon for which the
soil meets all of the required criteria.                                 A.        Soils that have:
    The family level is determined, in a similar manner, after
                                                                              1.     Permafrost within 100 cm of the soil surface; or
the subgroup has been determined. Chapter 17 can be used,
as one would use other keys in this taxonomy, to determine                    2. Gelic materials within 100 cm of the soil surface and
which components are part of the family. The family, however,                 permafrost within 200 cm of the soil surface.
typically has more than one component, and therefore the entire                                                             Gelisols, p. 145
chapter must be used. The keys to control sections for classes
                                                                         B.    Other soils that:
used as components of a family must be used to determine the
control section before use of the keys to classes.                            1. Do not have andic soil properties in 60 percent or more
    The descriptions and definitions of individual soil series are            of the thickness between the soil surface and either a depth
32                                                                                                                                            Keys to Soil Taxonomy



     of 60 cm or a densic, lithic, or paralithic contact or duripan if                                    coarse-loamy, loamy-skeletal, or finer and a frigid
     shallower; and                                                                                       temperature regime in the soil; or
     2. Have organic soil materials that meet one or more of the                                          (5) A cryic or gelic temperature regime in the soil;
     following:                                                                                           and
        a. Overlie cindery, fragmental, or pumiceous materials                                       b. An upper boundary within the following depths from
        and/or fill their interstices1 and directly below these                                      the mineral soil surface: either
        materials, have a densic, lithic, or paralithic contact; or
                                                                                                          (1)     Less than 50 cm; or
        b. When added with the underlying cindery, fragmental,
        or pumiceous materials, total 40 cm or more between the                                           (2) Less than 200 cm if the soil meets the sandy
        soil surface and a depth of 50 cm; or                                                             particle-size class criteria in at least some part between
                                                                                                          the mineral soil surface and the spodic horizon; and
        c. Constitute two-thirds or more of the total thickness of
        the soil to a densic, lithic, or paralithic contact and have                                 c. A lower boundary as follows:
        no mineral horizons or have mineral horizons with a total                                         (1) Either at a depth of 25 cm or more below the
        thickness of 10 cm or less; or                                                                    mineral soil surface or at the top of a duripan or
        d. Are saturated with water for 30 days or more per year                                          fragipan or at a densic, lithic, paralithic, or petroferric
        in normal years (or are artificially drained), have an upper                                      contact, whichever is shallowest; or
        boundary within 40 cm of the soil surface, and have a                                             (2) At any depth,
        total thickness of either:
                                                                                                                (a) If the spodic horizon meets the criteria for a
             (1) 60 cm or more if three-fourths or more of their                                                coarse-loamy, loamy-skeletal, or finer particle-size
             volume consists of moss fibers or if their bulk density,                                           class and the soil has a frigid temperature regime; or
             moist, is less than 0.1 g/cm3; or
                                                                                                                (b) If the soil has a cryic or gelic temperature
             (2) 40 cm or more if they consist either of sapric                                                 regime; and
             or hemic materials, or of fibric materials with less
             than three-fourths (by volume) moss fibers and a bulk                                   d.    Either:
             density, moist, of 0.1 g/cm3 or more.                                                        (1) A directly overlying albic horizon in 50 percent or
                                                     Histosols, p. 155                                    more of each pedon; or

C. Other soils that do not have a plaggen epipedon or an                                                  (2) No andic soil properties in 60 percent or more of
argillic or kandic horizon above a spodic horizon, and have one                                           the thickness either:
or more of the following:                                                                                       (a) Within 60 cm either of the mineral soil surface
     1. A spodic horizon, an albic horizon in 50 percent or                                                     or of the top of an organic layer with andic soil
     more of each pedon, and a cryic or gelic soil temperature                                                  properties, whichever is shallower, if there is no
     regime; or                                                                                                 densic, lithic, or paralithic contact, duripan, or
                                                                                                                petrocalcic horizon within that depth; or
     2. An Ap horizon containing 85 percent or more spodic
     materials; or                                                                                              (b) Between either the mineral soil surface or the
                                                                                                                top of an organic layer with andic soil properties,
     3. A spodic horizon with all of the following                                                              whichever is shallower, and a densic, lithic, or
     characteristics:                                                                                           paralithic contact, a duripan, or a petrocalcic
        a. One or more of the following:                                                                        horizon.
                                                                                                                                                     Spodosols, p. 257
             (1) A thickness of 10 cm or more; or
             (2) An overlying Ap horizon; or                                                   D. Other soils that have andic soil properties in 60 percent or
                                                                                               more of the thickness either:
             (3) Cementation in 50 percent or more of each
             pedon; or                                                                            1. Within 60 cm either of the mineral soil surface or of the
                                                                                                  top of an organic layer with andic soil properties, whichever
             (4) A particle-size class that meets the criteria for
                                                                                                  is shallower, if there is no densic, lithic, or paralithic contact,
                                                                                                  duripan, or petrocalcic horizon within that depth; or
    1
      Materials that meet the definition of cindery, fragmental, or pumiceous but have more
than 10 percent, by volume, voids that are filled with organic soil materials are considered
                                                                                                  2. Between either the mineral soil surface or the top
to be organic soil materials.                                                                     of an organic layer with andic soil properties, whichever
Identification of the Taxonomic Class of a Soil                                                                                                                      33



     is shallower, and a densic, lithic, or paralithic contact, a                                         b. A moisture control section that is dry in some or all
     duripan, or a petrocalcic horizon.                                                                   parts at some time during normal years; and
                                                       Andisols, p. 77
                                                                                                          c. No sulfuric horizon within 150 cm of the mineral soil
                                                                                                          surface.
E.       Other soils that have either:
                                                                                                                                                   Aridisols, p. 97
     1. An oxic horizon within 150 cm of the mineral soil
     surface and no kandic horizon within that depth; or                                       H.        Other soils that have either:                                    I
     2. 40 percent or more (by weight) clay in the fine-earth                                                                                                             D
                                                                                                    1. An argillic or kandic horizon, but no fragipan, and a base         E
     fraction between the mineral soil surface and a depth of                                       saturation (by sum of cations) of less than 35 percent at one
     18 cm (after mixing) and a kandic horizon that has the                                         of the following depths:
     weatherable-mineral properties of an oxic horizon and has its
     upper boundary within 100 cm of the mineral soil surface.                                            a. If the epipedon meets sandy or sandy-skeletal
                                                    Oxisols, p. 241                                       particle-size class criteria throughout, either:
                                                                                                             (1) 125 cm below the upper boundary of the argillic
F. Other soils that have:                                                                                    horizon (but no deeper than 200 cm below the mineral
     1. A layer 25 cm or more thick, within 100 cm of the                                                    soil surface) or 180 cm below the mineral soil surface,
     mineral soil surface, that has either slickensides or wedge-                                            whichever is deeper; or
     shaped peds that have their long axes tilted 10 to 60 degrees                                           (2) At a densic, lithic, paralithic, or petroferric
     from the horizontal; and                                                                                contact if shallower; or
     2. A weighted average of 30 percent or more clay in the                                              b. The shallowest of the following depths:
     fine-earth fraction either between the mineral soil surface and
     a depth of 18 cm or in an Ap horizon, whichever is thicker,                                             (1) 125 cm below the upper boundary of the argillic
     and 30 percent or more clay in the fine-earth fraction of all                                           or kandic horizon; or
     horizons between a depth of 18 cm and either a depth of 50                                              (2)     180 cm below the mineral soil surface; or
     cm or a densic, lithic, or paralithic contact, a duripan, or a
     petrocalcic horizon if shallower; and                                                                   (3) At a densic, lithic, paralithic, or petroferric
                                                                                                             contact; or
     3.     Cracks2 that open and close periodically.
                                                     Vertisols, p. 287                              2. A fragipan and both of the following:
                                                                                                          a. Either an argillic or a kandic horizon above, within, or
G.        Other soils that:                                                                               below it or clay films 1 mm or more thick in one or more
     1.     Have:                                                                                         of its subhorizons; and

           a. An aridic soil moisture regime; and                                                         b. A base saturation (by sum of cations) of less than 35
                                                                                                          percent at the shallowest of the following depths:
           b. An ochric or anthropic epipedon; and
                                                                                                             (1)     75 cm below the upper boundary of the fragipan;
           c. One or more of the following within 100 cm of the                                              or
           soil surface: a cambic horizon with a lower depth of 25
           cm or more; a cryic soil temperature regime and a cambic                                          (2)     200 cm below the mineral soil surface; or
           horizon; a calcic, gypsic, petrocalcic, petrogypsic, or salic                                     (3) At a densic, lithic, paralithic, or petroferric
           horizon; or a duripan; or                                                                         contact.
           d. An argillic or natric horizon; or                                                                                                        Ultisols, p. 267

     2.     Have a salic horizon; and
                                                                                               I.    Other soils that have both of the following:
           a. Saturation with water in one or more layers within
                                                                                                    1.     Either:
           100 cm of the soil surface for 1 month or more during a
           normal year; and                                                                               a. A mollic epipedon; or
                                                                                                          b. Both a surface horizon that meets all the requirements
     2
       A crack is a separation between gross polyhedrons. If the surface is strongly self-                for a mollic epipedon except thickness after the soil
mulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the               has been mixed to a depth of 18 cm and a subhorizon
cracks may be filled mainly by granular materials from the surface, but they are open in
the sense that the polyhedrons are separated. A crack is regarded as open if it controls the              more than 7.5 cm thick, within the upper part of an
infiltration and percolation of water in a dry, clayey soil.                                              argillic, kandic, or natric horizon, that meets the color,
34



           organic-carbon content, base saturation, and structure              d. A sulfuric horizon within 150 cm of the mineral soil
           requirements of a mollic epipedon but is separated from             surface; or
           the surface horizon by an albic horizon; and
                                                                               e. A cryic or gelic soil temperature regime and a cambic
     2. A base saturation of 50 percent or more (by NH4OAc)                    horizon; or
     in all horizons either between the upper boundary of any
                                                                             2. No sulfidic materials within 50 cm of the mineral soil
     argillic, kandic, or natric horizon and a depth of 125 cm
                                                                             surface; and both:
     below that boundary, or between the mineral soil surface
     and a depth of 180 cm, or between the mineral soil surface                a. In one or more horizons between 20 and 50 cm
     and a densic, lithic, or paralithic contact, whichever depth is           below the mineral soil surface, either an n value of 0.7 or
     shallowest.                                                               less or less than 8 percent clay in the fine-earth fraction;
                                                    Mollisols, p. 197          and
                                                                               b.    One or both of the following:
J. Other soils that do not have a plaggen epipedon and that
have either:                                                                        (1) A salic horizon or a histic, mollic, plaggen, or
                                                                                    umbric epipedon; or
     1. An argillic, kandic, or natric horizon; or
                                                                                    (2) In 50 percent or more of the layers between
     2. A fragipan that has clay films 1 mm or more thick in
                                                                                    the mineral soil surface and a depth of 50 cm, an
     some part.
                                                                                    exchangeable sodium percentage of 15 or more (or
                                                  Alfisols, p. 35
                                                                                    a sodium adsorption ratio of 13 or more), which
                                                                                    decreases with increasing depth below 50 cm, and also
K.        Other soils that have either:
                                                                                    ground water within 100 cm of the mineral soil surface
     1.     One or more of the following:                                           at some time during the year when the soil is not frozen
                                                                                    in any part.
           a. A cambic horizon that is within 100 cm of the mineral
                                                                                                                         Inceptisols, p. 161
           soil surface and has a lower boundary at a depth of 25 cm
           or more below the mineral soil surface; or
                                                                        L.    Other soils.
           b. A calcic, petrocalcic, gypsic, petrogypsic, or placic                                                         Entisols, p. 123
           horizon or a duripan within a depth of 100 cm of the
           mineral soil surface; or
           c. A fragipan or an oxic, sombric, or spodic horizon
           within 200 cm of the mineral soil surface; or
                                                                                                                                     35




CHAPTER 5

                                                                                                                          Alfisols

Key to Suborders                                                      JAB. Other Aqualfs that have one or more horizons, at a depth
                                                                      between 30 and 150 cm from the mineral soil surface, in which       A
JA. Alfisols that have, in one or more horizons within 50                                                                                 L
                                                                      plinthite either forms a continuous phase or constitutes one-half   F
cm of the mineral soil surface, aquic conditions (other than          or more of the volume.
anthraquic conditions) for some time in normal years (or                                                          Plinthaqualfs, p. 43
artificial drainage) and have one or both of the following:
   1. Redoximorphic features in all layers between either the         JAC. Other Aqualfs that have a duripan.
   lower boundary of an Ap horizon or a depth of 25 cm below                                                          Duraqualfs, p. 37
   the mineral soil surface, whichever is deeper, and a depth of
   40 cm; and one of the following within the upper 12.5 cm of        JAD. Other Aqualfs that have a natric horizon.
   the argillic, natric, glossic, or kandic horizon:                                                             Natraqualfs, p. 43

      a. 50 percent or more redox depletions with chroma of           JAE. Other Aqualfs that have a fragipan within 100 cm of the
      2 or less on faces of peds and redox concentrations within      mineral soil surface.
      peds; or                                                                                                 Fragiaqualfs, p. 41
      b. Redox concentrations and 50 percent or more redox
      depletions with chroma of 2 or less in the matrix; or           JAF.   Other Aqualfs that have a kandic horizon.
                                                                                                                 Kandiaqualfs, p. 42
      c. 50 percent or more redox depletions with chroma of 1
      or less on faces of peds or in the matrix, or both; or          JAG. Other Aqualfs that have one or more layers, at least
   2. In the horizons that have aquic conditions, enough              25 cm thick (cumulative) within 100 cm of the mineral soil
   active ferrous iron to give a positive reaction to alpha,alpha-    surface, that have 50 percent or more (by volume) recognizable
   dipyridyl at a time when the soil is not being irrigated.          bioturbation, such as filled animal burrows, wormholes, or
                                                     Aqualfs, p. 35   casts.
                                                                                                                   Vermaqualfs, p. 43
JB. Other Alfisols that have a cryic or isofrigid soil
temperature regime.                                                   JAH. Other Aqualfs that have an abrupt textural change
                                                   Cryalfs, p. 44     between the ochric epipedon or albic horizon and the argillic
                                                                      horizon and have a saturated hydraulic conductivity of 0.4
JC.   Other Alfisols that have an ustic soil moisture regime.         cm/hr or slower (moderately low or lower Ksat class) in the
                                                     Ustalfs, p. 59   argillic horizon.
                                                                                                                   Albaqualfs, p. 36
JD. Other Alfisols that have a xeric soil moisture regime.
                                                  Xeralfs, p. 71      JAI. Other Aqualfs that have a glossic horizon.
                                                                                                                 Glossaqualfs, p. 41
JE.   Other Alfisols.
                                                     Udalfs, p. 47    JAJ.   Other Aqualfs that have episaturation.
                                                                                                                      Epiaqualfs, p. 39
Aqualfs
                                                                      JAK. Other Aqualfs.
Key to Great Groups                                                                                               Endoaqualfs, p. 37
JAA. Aqualfs that have a cryic soil temperature regime.
                                            Cryaqualfs, p. 37
36                                                                                                            Keys to Soil Taxonomy



Albaqualfs                                                             1. Cracks within 125 cm of the mineral soil surface that are
                                                                       5 mm or more wide through a thickness of 30 cm or more
Key to Subgroups                                                       for some time in normal years and slickensides or wedge-
JAHA. Albaqualfs that meet sandy or sandy-skeletal particle-           shaped peds in a layer 15 cm or more thick that has its upper
size class criteria throughout a layer extending from the mineral      boundary within 125 cm of the mineral soil surface; or
soil surface to the top of an argillic horizon at a depth of 50 cm     2. A linear extensibility of 6.0 cm or more between the
or more below the mineral soil surface.                                mineral soil surface and either a depth of 100 cm or a densic,
                                                Arenic Albaqualfs      lithic, or paralithic contact, whichever is shallower.
                                                                                                                     Vertic Albaqualfs
JAHB.          Other Albaqualfs that have both of the following:
     1.    One or both:                                              JAHE. Other Albaqualfs that have both:
          a. Cracks within 125 cm of the mineral soil surface that     1. Chroma of 3 or more in 40 percent or more of the matrix
          are 5 mm or more wide through a thickness of 30 cm or        between the lower boundary of the A or Ap horizon and a
          more for some time in normal years and slickensides or       depth of 75 cm from the mineral soil surface; and
          wedge-shaped peds in a layer 15 cm or more thick that
                                                                       2. A mollic epipedon, or the upper 18 cm of the mineral
          has its upper boundary within 125 cm of the mineral soil
                                                                       soil meets all of the requirements for a mollic epipedon,
          surface; or
                                                                       except for thickness, after mixing.
          b. A linear extensibility of 6.0 cm or more between                                                    Udollic Albaqualfs
          the mineral soil surface and either a depth of 100 cm
          or a densic, lithic, or paralithic contact, whichever is   JAHF. Other Albaqualfs that have chroma of 3 or more in 40
          shallower; and                                             percent or more of the matrix between the lower boundary of
                                                                     the A or Ap horizon and a depth of 75 cm from the mineral soil
     2. Chroma of 3 or more in 40 percent or more of the matrix
                                                                     surface.
     between the lower boundary of the A or Ap horizon and a
                                                                                                                  Aeric Albaqualfs
     depth of 75 cm from the mineral soil surface.
                                         Aeric Vertic Albaqualfs
                                                                     JAHG. Other Albaqualfs that have, throughout one or more
                                                                     horizons with a total thickness of 18 cm or more within 75 cm
JAHC.          Other Albaqualfs that have both of the following:
                                                                     of the mineral soil surface, one or more of the following:
     1.    One or both:
                                                                       1. A fine-earth fraction with both a bulk density of 1.0
          a. Cracks within 125 cm of the mineral soil surface that     g/cm3 or less, measured at 33 kPa water retention, and Al
          are 5 mm or more wide through a thickness of 30 cm or        plus 1/2 Fe percentages (by ammonium oxalate) totaling more
          more for some time in normal years and slickensides or       than 1.0; or
          wedge-shaped peds in a layer 15 cm or more thick that
          has its upper boundary within 125 cm of the mineral soil     2. More than 35 percent (by volume) fragments coarser
          surface; or                                                  than 2.0 mm, of which more than 66 percent is cinders,
                                                                       pumice, and pumicelike fragments; or
          b. A linear extensibility of 6.0 cm or more between
          the mineral soil surface and either a depth of 100 cm        3. A fine-earth fraction containing 30 percent or more
          or a densic, lithic, or paralithic contact, whichever is     particles 0.02 to 2.0 mm in diameter; and
          shallower; and                                                  a. In the 0.02 to 2.0 mm fraction, 5 percent or more
     2. An Ap horizon or materials between the mineral soil               volcanic glass; and
     surface and a depth of 18 cm that, after mixing, have one or
                                                                          b. [(Al plus 1/2 Fe, percent extracted by ammonium
     more of the following:
                                                                          oxalate) times 60] plus the volcanic glass (percent) is
          a. A color value, moist, of 4 or more; or                       equal to 30 or more.
                                                                                                               Aquandic Albaqualfs
          b. A color value, dry, of 6 or more; or
          c.    Chroma of 4 or more.
                                         Chromic Vertic Albaqualfs   JAHH. Other Albaqualfs that have a mollic epipedon, or the
                                                                     upper 18 cm of the mineral soil meets all of the requirements
JAHD. Other Albaqualfs that have one or both of the                  for a mollic epipedon, except for thickness, after mixing.
following:                                                                                                          Mollic Albaqualfs
Alfisols                                                                                                                             37



JAHI. Other Albaqualfs that have an umbric epipedon, or the               has its upper boundary within 125 cm of the mineral soil
upper 18 cm of the mineral soil meets all of the requirements             surface; or
for an umbric epipedon, except for thickness, after mixing.
                                                                          b. A linear extensibility of 6.0 cm or more between
                                             Umbric Albaqualfs
                                                                          the mineral soil surface and either a depth of 100 cm
                                                                          or a densic, lithic, or paralithic contact, whichever is
JAHJ.      Other Albaqualfs.
                                                                          shallower; and
                                               Typic Albaqualfs
                                                                     2. An Ap horizon or materials between the mineral soil
Cryaqualfs                                                           surface and a depth of 18 cm that, after mixing, have one or
                                                                     more of the following:
Key to Subgroups
                                                                          a. A color value, moist, of 4 or more; or                       A
JAAA. All Cryaqualfs (provisionally).                                                                                                     L
                                                                                                                                          F
                                               Typic Cryaqualfs           b. A color value, dry, of 6 or more; or
                                                                          c.    Chroma of 4 or more.
Duraqualfs                                                                                              Chromic Vertic Endoaqualfs
Key to Subgroups
                                                                   JAKC. Other Endoaqualfs that have one or both of the
JACA. All Duraqualfs (provisionally).                              following:
                                               Typic Duraqualfs
                                                                     1. Cracks within 125 cm of the mineral soil surface that are
                                                                     5 mm or more wide through a thickness of 30 cm or more
Endoaqualfs                                                          for some time in normal years and slickensides or wedge-
Key to Subgroups                                                     shaped peds in a layer 15 cm or more thick that has its upper
                                                                     boundary within 125 cm of the mineral soil surface; or
JAKA. Endoaqualfs that have, throughout one or more
                                                                     2. A linear extensibility of 6.0 cm or more between the
horizons with a total thickness of 18 cm or more within 75 cm
                                                                     mineral soil surface and either a depth of 100 cm or a densic,
of the mineral soil surface, one or more of the following:
                                                                     lithic, or paralithic contact, whichever is shallower.
   1. A fine-earth fraction with both a bulk density of 1.0                                                      Vertic Endoaqualfs
   g/cm3 or less, measured at 33 kPa water retention, and Al
   plus 1/2 Fe percentages (by ammonium oxalate) totaling more     JAKD. Other Endoaqualfs that have both:
   than 1.0; or
                                                                     1.    Fragic soil properties:
   2. More than 35 percent (by volume) fragments coarser
                                                                          a. In 30 percent or more of the volume of a layer 15 cm
   than 2.0 mm, of which more than 66 percent is cinders,
                                                                          or more thick that has its upper boundary within 100 cm
   pumice, and pumicelike fragments; or
                                                                          of the mineral soil surface; or
   3. A fine-earth fraction containing 30 percent or more
                                                                          b. In 60 percent or more of the volume of a layer 15 cm
   particles 0.02 to 2.0 mm in diameter; and
                                                                          or more thick; and
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                                                     2. In one or more horizons between the A or Ap horizon
        volcanic glass; and
                                                                     and a depth of 75 cm below the mineral soil surface, one or a
        b. [(Al plus 1/2 Fe, percent extracted by ammonium           combination of the following colors:
        oxalate) times 60] plus the volcanic glass (percent) is
                                                                          a. Hue of 7.5YR or redder in 50 percent or more of the
        equal to 30 or more.
                                                                          matrix; and
                                           Aquandic Endoaqualfs
                                                                               (1) If peds are present, chroma of 2 or more on 50
JAKB.      Other Endoaqualfs that have both of the following:                  percent or more of ped exteriors or no redox depletions
                                                                               with chroma of 2 or less in ped interiors; or
   1.    One or both:
                                                                               (2) If peds are absent, chroma of 2 or more in 50
        a. Cracks within 125 cm of the mineral soil surface that
                                                                               percent or more of the matrix; or
        are 5 mm or more wide through a thickness of 30 cm or
        more for some time in normal years and slickensides or            b. In 50 percent or more of the matrix, hue of 10YR or
        wedge-shaped peds in a layer 15 cm or more thick that             yellower and either:
38                                                                                                               Keys to Soil Taxonomy



          (1) Both a color value of 3 or more (moist) and              JAKI. Other Endoaqualfs that have both:
          chroma of 3 or more (moist and dry); or
                                                                          1. An umbric epipedon, or the upper 18 cm of the mineral
          (2) Chroma of 2 or more if there are no redox                   soil meets all of the requirements for an umbric epipedon,
          concentrations.                                                 except for thickness, after mixing; and
                                   Aeric Fragic Endoaqualfs
                                                                          2. In one or more horizons between the A or Ap horizon
JAKE.      Other Endoaqualfs that have fragic soil properties:            and a depth of 75 cm below the mineral soil surface, one or a
                                                                          combination of the following colors:
     1. In 30 percent or more of the volume of a layer 15 cm or
     more thick that has its upper boundary within 100 cm of the               a. Hue of 7.5YR or redder in 50 percent or more of the
     mineral soil surface; or                                                  matrix; and

     2. In 60 percent or more of the volume of a layer 15 cm or                  (1) If peds are present, chroma of 2 or more on 50
     more thick.                                                                 percent or more of ped exteriors or no redox depletions
                                           Fragic Endoaqualfs                    with chroma of 2 or less in ped interiors; or
                                                                                 (2) If peds are absent, chroma of 2 or more in 50
JAKF. Other Endoaqualfs that meet sandy or sandy-skeletal
                                                                                 percent or more of the matrix; or
particle-size class criteria throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth of           b. In 50 percent or more of the matrix, hue of 10YR or
50 to 100 cm below the mineral soil surface.                                   yellower and either:
                                              Arenic Endoaqualfs
                                                                                 (1) Both a color value of 3 or more (moist) and
JAKG. Other Endoaqualfs that meet sandy or sandy-skeletal                        chroma of 3 or more; or
particle-size class criteria throughout a layer extending from the               (2) Chroma of 2 or more if there are no redox
mineral soil surface to the top of an argillic horizon at a depth of             concentrations.
100 cm or more below the mineral soil surface.                                                          Aeric Umbric Endoaqualfs
                                        Grossarenic Endoaqualfs
                                                                       JAKJ. Other Endoaqualfs that have, in one or more horizons
JAKH. Other Endoaqualfs that have both:                                between the A or Ap horizon and a depth of 75 cm below the
     1. A mollic epipedon, or the upper 18 cm of the mineral           mineral soil surface, in 50 percent or more of the matrix, one or
     soil meets all of the requirements for a mollic epipedon,         a combination of the following colors:
     except for thickness, after mixing; and
                                                                          1.    Hue of 7.5YR or redder; and
     2. In one or more horizons between the A or Ap horizon
                                                                               a. If peds are present, chroma of 2 or more (both moist
     and a depth of 75 cm below the mineral soil surface, one or a
                                                                               and dry) on 50 percent or more of ped exteriors or no
     combination of the following colors:
                                                                               redox depletions with chroma of 2 or less (both moist and
       a. Hue of 7.5YR or redder in 50 percent or more of the                  dry) in ped interiors; or
       matrix; and
                                                                               b. If peds are absent, chroma of 2 or more (both moist
          (1) If peds are present, chroma of 2 or more on 50                   and dry); or
          percent or more of ped exteriors or no redox depletions
          with chroma of 2 or less in ped interiors; or                   2.    Hue of 10YR or yellower and either:

          (2) If peds are absent, chroma of 2 or more in 50                    a. Both a color value of 3 or more (moist) and chroma
          percent or more of the matrix; or                                    of 3 or more (moist and dry); or

       b. In 50 percent or more of the matrix, hue of 10YR or                  b. Chroma of 2 or more (both moist and dry) and no
       yellower and either:                                                    redox concentrations.
                                                                                                                  Aeric Endoaqualfs
          (1) Both a color value of 3 or more (moist) and
          chroma of 3 or more; or                                      JAKK. Other Endoaqualfs that have a mollic epipedon, or the
          (2) Chroma of 2 or more if there are no redox                upper 18 cm of the mineral soil meets all of the requirements
          concentrations.                                              for a mollic epipedon, except for thickness, after mixing.
                                          Udollic Endoaqualfs                                                      Mollic Endoaqualfs
Alfisols                                                                                                                                39



JAKL. Other Endoaqualfs that have an umbric epipedon,                JAJB.        Other Epiaqualfs that have both of the following:
or the upper 18 cm of the mineral soil meets all of the
                                                                       1.     One or both:
requirements for an umbric epipedon, except for thickness, after
mixing.                                                                      a. Cracks within 125 cm of the mineral soil surface that
                                          Umbric Endoaqualfs                 are 5 mm or more wide through a thickness of 30 cm or
                                                                             more for some time in normal years and slickensides or
JAKM.        Other Endoaqualfs.                                              wedge-shaped peds in a layer 15 cm or more thick that
                                                Typic Endoaqualfs            has its upper boundary within 125 cm of the mineral soil
                                                                             surface; or
Epiaqualfs                                                                   b. A linear extensibility of 6.0 cm or more between
Key to Subgroups                                                             the mineral soil surface and either a depth of 100 cm           A
                                                                                                                                             L
                                                                             or a densic, lithic, or paralithic contact, whichever is        F
JAJA. Epiaqualfs that have all of the following:
                                                                             shallower; and
   1.    One or both:
                                                                       2. In one or more horizons between the A or Ap horizon
        a. Cracks within 125 cm of the mineral soil surface that       and a depth of 75 cm below the mineral soil surface, in 50
        are 5 mm or more wide through a thickness of 30 cm or          percent or more of the matrix, one or a combination of the
        more for some time in normal years and slickensides or         following colors:
        wedge-shaped peds in a layer 15 cm or more thick that
                                                                             a.    Hue of 7.5YR or redder; and
        has its upper boundary within 125 cm of the mineral soil
        surface; or                                                               (1) If peds are present, chroma of 2 or more (both
                                                                                  moist and dry) on 50 percent or more of ped exteriors
        b. A linear extensibility of 6.0 cm or more between
                                                                                  or no redox depletions with chroma of 2 or less (both
        the mineral soil surface and either a depth of 100 cm
                                                                                  moist and dry) in ped interiors; or
        or a densic, lithic, or paralithic contact, whichever is
        shallower; and                                                            (2) If peds are absent, chroma of 2 or more (both
                                                                                  moist and dry); or
   2. In one or more horizons between the A or Ap horizon
   and a depth of 75 cm below the mineral soil surface, in 50                b.    Hue of 10YR or yellower and either:
   percent or more of the matrix, one or a combination of the
                                                                                  (1) Both a color value of 3 or more (moist) and
   following colors:
                                                                                  chroma of 3 or more (moist and dry); or
        a.    Hue of 7.5YR or redder; and
                                                                                  (2) Chroma of 2 or more (both moist and dry) and no
             (1) If peds are present, chroma of 2 or more (both                   redox concentrations.
             moist and dry) on 50 percent or more of ped exteriors                                           Aeric Vertic Epiaqualfs
             or no redox depletions with chroma of 2 or less (both
             moist and dry) in ped interiors; or                     JAJC.        Other Epiaqualfs that have both of the following:
             (2) If peds are absent, chroma of 2 or more (both         1.     One or both:
             moist and dry); or
                                                                             a. Cracks within 125 cm of the mineral soil surface that
        b.    Hue of 10YR or yellower and either:                            are 5 mm or more wide through a thickness of 30 cm or
             (1) Both a color value of 3 or more (moist) and                 more for some time in normal years and slickensides or
             chroma of 3 or more (moist and dry); or                         wedge-shaped peds in a layer 15 cm or more thick that
                                                                             has its upper boundary within 125 cm of the mineral soil
             (2) Chroma of 2 or more (both moist and dry) and no             surface; or
             redox concentrations; and
                                                                             b. A linear extensibility of 6.0 cm or more between
   3. An Ap horizon or materials between the mineral soil                    the mineral soil surface and either a depth of 100 cm
   surface and a depth of 18 cm that, after mixing, have one or              or a densic, lithic, or paralithic contact, whichever is
   more of the following:                                                    shallower; and
        a. A color value, moist, of 4 or more; or                      2. An Ap horizon or materials between the mineral soil
        b. A color value, dry, of 6 or more; or                        surface and a depth of 18 cm that, after mixing, have one or
                                                                       more of the following:
        c.    Chroma of 4 or more.
                               Aeric Chromic Vertic Epiaqualfs               a. A color value, moist, of 4 or more; or
40                                                                                                                   Keys to Soil Taxonomy



          b. A color value, dry, of 6 or more; or                                   moist and dry) on 50 percent or more of ped exteriors
                                                                                    or no redox depletions with chroma of 2 or less (both
          c.     Chroma of 4 or more.
                                                                                    moist and dry) in ped interiors; or
                                           Chromic Vertic Epiaqualfs
                                                                                    (2) If peds are absent, chroma of 2 or more (both
JAJD. Other Epiaqualfs that have one or both of the following:                      moist and dry); or
     1. Cracks within 125 cm of the mineral soil surface that are              b.    Hue of 10YR or yellower and either:
     5 mm or more wide through a thickness of 30 cm or more
                                                                                    (1) Both a color value of 3 or more (moist) and
     for some time in normal years and slickensides or wedge-
                                                                                    chroma of 3 or more (moist and dry); or
     shaped peds in a layer 15 cm or more thick that has its upper
     boundary within 125 cm of the mineral soil surface; or                         (2) Chroma of 2 or more (both moist and dry) and no
                                                                                    redox concentrations.
     2. A linear extensibility of 6.0 cm or more between the
                                                                                                               Aeric Fragic Epiaqualfs
     mineral soil surface and either a depth of 100 cm or a densic,
     lithic, or paralithic contact, whichever is shallower.
                                                                       JAJG.        Other Epiaqualfs that have fragic soil properties:
                                                   Vertic Epiaqualfs
                                                                          1. In 30 percent or more of the volume of a layer 15 cm or
JAJE. Other Epiaqualfs that have, throughout one or more                  more thick that has its upper boundary within 100 cm of the
horizons with a total thickness of 18 cm or more within 75 cm             mineral soil surface; or
of the mineral soil surface, one or more of the following:
                                                                          2. In 60 percent or more of the volume of a layer 15 cm or
     1. A fine-earth fraction with both a bulk density of 1.0             more thick.
     g/cm3 or less, measured at 33 kPa water retention, and Al                                                    Fragic Epiaqualfs
     plus 1/2 Fe percentages (by ammonium oxalate) totaling more
     than 1.0; or                                                      JAJH. Other Epiaqualfs that meet sandy or sandy-skeletal
                                                                       particle-size class criteria throughout a layer extending from the
     2. More than 35 percent (by volume) fragments coarser
                                                                       mineral soil surface to the top of an argillic horizon at a depth of
     than 2.0 mm, of which more than 66 percent is cinders,
                                                                       50 to 100 cm below the mineral soil surface.
     pumice, and pumicelike fragments; or
                                                                                                                       Arenic Epiaqualfs
     3. A fine-earth fraction containing 30 percent or more
     particles 0.02 to 2.0 mm in diameter; and                         JAJI. Other Epiaqualfs that meet sandy or sandy-skeletal
                                                                       particle-size class criteria throughout a layer extending from the
          a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                                                       mineral soil surface to the top of an argillic horizon at a depth of
          volcanic glass; and
                                                                       100 cm or more below the mineral soil surface.
          b. [(Al plus 1/2 Fe, percent extracted by ammonium                                                     Grossarenic Epiaqualfs
          oxalate) times 60] plus the volcanic glass (percent) is
          equal to 30 or more.                                         JAJJ.    Other Epiaqualfs that have both:
                                               Aquandic Epiaqualfs
                                                                          1. An umbric epipedon, or the upper 18 cm of the mineral
                                                                          soil meets all of the requirements for an umbric epipedon,
JAJF.          Other Epiaqualfs that have both:
                                                                          except for thickness, after mixing; and
     1.    Fragic soil properties:
                                                                          2. In one or more horizons between the A or Ap horizon
          a. In 30 percent or more of the volume of a layer 15 cm         and a depth of 75 cm below the mineral soil surface, in 50
          or more thick that has its upper boundary within 100 cm         percent or more of the matrix, one or a combination of the
          of the mineral soil surface; or                                 following colors:
          b. In 60 percent or more of the volume of a layer 15 cm              a.    Hue of 7.5YR or redder; and
          or more thick; and
                                                                                    (1) If peds are present, chroma of 2 or more (both
     2. In one or more horizons between the A or Ap horizon                         moist and dry) on 50 percent or more of ped exteriors
     and a depth of 75 cm below the mineral soil surface, in 50                     or no redox depletions with chroma of 2 or less (both
     percent or more of the matrix, one or a combination of the                     moist and dry) in ped interiors; or
     following colors:
                                                                                    (2) If peds are absent, chroma of 2 or more (both
          a.     Hue of 7.5YR or redder; and                                        moist and dry); or
                (1)   If peds are present, chroma of 2 or more (both           b.    Hue of 10YR or yellower and either:
Alfisols	                                                                                                                               41



            (1)	 Both	a	color	value	of	3	or	more	(moist)	and	          upper	18	cm	of	the	mineral	soil	meets	all	of	the	requirements	
            chroma	of	3	or	more	(moist	and	dry);	or                    for	a	mollic	epipedon,	except	for	thickness,	after	mixing.
                                                                                                                      Mollic Epiaqualfs
            (2)	 Chroma	of	2	or	more	(both	moist	and	dry)	and	no	
            redox	concentrations.
                                                                       JAJN.	 Other	Epiaqualfs	that	have	an	umbric	epipedon,	or	the	
                                       Aeric Umbric Epiaqualfs
                                                                       upper	18	cm	of	the	mineral	soil	meets	all	of	the	requirements	
                                                                       for	an	umbric	epipedon,	except	for	thickness,	after	mixing.
JAJK.	 Other	Epiaqualfs	that	have	both:
                                                                                                                    Umbric Epiaqualfs
   1.	 A	mollic	epipedon,	or	the	upper	18	cm	of	the	mineral	
   soil	meets	all	of	the	requirements	for	a	mollic	epipedon,	          JAJO.	 Other	Epiaqualfs.
   except	for	thickness,	after	mixing	and                                                                               Typic Epiaqualfs       A
                                                                                                                                               L
   2.	 In	50	percent	or	more	of	the	matrix	in	one	or	more	                                                                                     F
   horizons	between	the	A	or	Ap	horizon	and	a	depth	of	75	cm	          Fragiaqualfs
   below	the	mineral	soil	surface,	one	or	a	combination	of	the	        Key to Subgroups
   following	colors:
                                                                       JAEA.	 Fragiaqualfs	that	have	one	or	more	layers,	at	least	
      a.	 Hue	of	7.5YR	or	redder;	and                                  25	cm	thick	(cumulative)	within	100	cm	of	the	mineral	soil	
            (1)	 If	peds	are	present,	chroma	of	2	or	more	on	50	       surface,	that	have	25	percent	or	more	(by	volume)	recognizable	
            percent	or	more	of	ped	exteriors	or	no	redox	depletions	   bioturbation,	such	as	filled	animal	burrows,	wormholes,	or	casts.
            with	chroma	of	2	or	less	in	ped	interiors;	or                                                         Vermic Fragiaqualfs

            (2)	 If	peds	are	absent,	chroma	of	2	or	more	in	50	        JAEB.	 Other	Fragiaqualfs	that	have,	between	the	A	or	Ap	
            percent	or	more	of	the	matrix;	or                          horizon	and	a	fragipan,	a	horizon	with	50	percent	or	more	
      b.	 Hue	of	10YR	or	yellower	and either:                          chroma	of	3	or	more	if	hue	is	10YR	or	redder	or	of	4	or	more	if	
                                                                       hue	is	2.5Y	or	yellower.
            (1)	 Both	a	color	value	of	3	or	more	(moist)	and	                                                      Aeric Fragiaqualfs
            chroma	of	3	or	more;	or
            (2)	 Chroma	of	2	or	more	if	there	are	no	redox	            JAEC.	 Other	Fragiaqualfs	that	have	5	percent	or	more	(by	
            concentrations.                                            volume)	plinthite	in	one	or	more	horizons	within	150	cm	of	the	
                                               Udollic Epiaqualfs      mineral	soil	surface.
                                                                                                                Plinthic Fragiaqualfs
JAJL.	 Other	Epiaqualfs	that	have,	in	one	or	more	horizons	
between	the	A	or	Ap	horizon	and	a	depth	of	75	cm	below	the	            JAED.	 Other	Fragiaqualfs	that	have	a	color	value,	moist,	
mineral	soil	surface,	in	50	percent	or	more	of	the	matrix,	one	or	     of	3	or	less	and	a	color	value,	dry,	of	5	or	less	(crushed	and	
a	combination	of	the	following	colors:                                 smoothed	sample)	either	throughout	the	upper	18	cm	of	the	
                                                                       mineral	soil	(unmixed)	or	between	the	mineral	soil	surface	and	a	
   1.	 Hue	of	7.5YR	or	redder;	and                                     depth	of	18	cm	after	mixing.
      a.	 If	peds	are	present,	chroma	of	2	or	more	(both	moist	                                                       Humic Fragiaqualfs
      and	dry)	on	50	percent	or	more	of	ped	exteriors	or	no	
      redox	depletions	with	chroma	of	2	or	less	(both	moist	and	       JAEE.	 Other	Fragiaqualfs.
      dry)	in	ped	interiors;	or                                                                                      Typic Fragiaqualfs

      b.	 If	peds	are	absent,	chroma	of	2	or	more	(both	moist	
                                                                       Glossaqualfs
      and	dry);	or
                                                                       Key to Subgroups
   2.	 Hue	of	10YR	or	yellower	and either:
                                                                       JAIA.	 Glossaqualfs	that	have	a	histic	epipedon.
      a.	 Both	a	color	value	of	3	or	more	(moist)	and	chroma	                                                     Histic Glossaqualfs
      of	3	or	more	(moist	and	dry);	or
      b.	 Chroma	of	2	or	more	(both	moist	and	dry)	and	no	             JAIB.	 Other	Glossaqualfs	that	meet	sandy	or	sandy-skeletal	
      redox	concentrations.                                            particle-size	class	criteria	throughout	a	layer	extending	from	the	
                                            Aeric Epiaqualfs           mineral	soil	surface	to	the	top	of	an	argillic	horizon	at	a	depth	of	
                                                                       50	cm	or	more	below	the	mineral	soil	surface.
JAJM.	 Other	Epiaqualfs	that	have	a	mollic	epipedon,	or	the	                                                         Arenic Glossaqualfs
42                                                                                                                Keys to Soil Taxonomy



JAIC. Other Glossaqualfs that have both:                                      a. Both a color value of 3 or more (moist) and chroma
                                                                              of 3 or more (moist and dry); or
     1.    Fragic soil properties:
                                                                              b. Chroma of 2 or more (both moist and dry) and no
          a. In 30 percent or more of the volume of a layer 15 cm             redox concentrations.
          or more thick that has its upper boundary within 100 cm                                                Aeric Glossaqualfs
          of the mineral soil surface; or
          b. In 60 percent or more of the volume of a layer 15 cm     JAIF. Other Glossaqualfs that have a mollic epipedon, or the
          or more thick; and                                          upper 18 cm of the mineral soil meets the requirements for a
                                                                      mollic epipedon after mixing.
     2. In one or more horizons between the A or Ap horizon                                                      Mollic Glossaqualfs
     and a depth of 75 cm below the mineral soil surface, one or a
     combination of the following colors:                             JAIG.        Other Glossaqualfs.
          a. Hue of 7.5YR or redder in 50 percent or more of the                                                        Typic Glossaqualfs
          matrix; and
                                                                      Kandiaqualfs
            (1) If peds are present, chroma of 2 or more on 50
            percent or more of ped exteriors or no redox depletions   Key to Subgroups
            with chroma of 2 or less in ped interiors; or             JAFA. Kandiaqualfs that meet sandy or sandy-skeletal
            (2) If peds are absent, chroma of 2 or more in 50         particle-size class criteria throughout a layer extending from the
            percent or more of the matrix; or                         mineral soil surface to the top of a kandic horizon at a depth of
                                                                      50 to 100 cm below the mineral soil surface.
          b. In 50 percent or more of the matrix, hue of 10YR or                                                   Arenic Kandiaqualfs
          yellower and either:
            (1) Both a color value of 3 or more (moist) and           JAFB. Other Kandiaqualfs that meet sandy or sandy-skeletal
            chroma of 3 or more (moist and dry); or                   particle-size class criteria throughout a layer extending from the
                                                                      mineral soil surface to the top of a kandic horizon at a depth of
            (2) Chroma of 2 or more if there are no redox             100 cm or more below the mineral soil surface.
            concentrations.                                                                                 Grossarenic Kandiaqualfs
                                     Aeric Fragic Glossaqualfs
                                                                      JAFC. Other Kandiaqualfs that have 5 percent or more (by
JAID. Other Glossaqualfs that have fragic soil properties:            volume) plinthite in one or more horizons within 150 cm of the
     1. In 30 percent or more of the volume of a layer 15 cm or       mineral soil surface.
     more thick that has its upper boundary within 100 cm of the                                              Plinthic Kandiaqualfs
     mineral soil surface; or
                                                                      JAFD.        Other Kandiaqualfs that have both:
     2. In 60 percent or more of the volume of a layer 15 cm or
     more thick.                                                         1. A color value, moist, of 3 or less and a color value, dry,
                                           Fragic Glossaqualfs           of 5 or less (crushed and smoothed sample) either throughout
                                                                         the upper 18 cm of the mineral soil (unmixed) or between the
JAIE. Other Glossaqualfs that have, in one or more horizons              mineral soil surface and a depth of 18 cm after mixing; and
between the A or Ap horizon and a depth of 75 cm below the               2. In one or more horizons between the A or Ap horizon
mineral soil surface, in 50 percent or more of the matrix, one or        and a depth of 75 cm below the mineral soil surface, in 50
a combination of the following colors:                                   percent or more of the matrix, one or a combination of the
     1.    Hue of 7.5YR or redder; and                                   following colors:
          a. If peds are present, chroma of 2 or more (both moist             a.    Hue of 7.5YR or redder; and
          and dry) on 50 percent or more of ped exteriors or no                    (1) If peds are present, chroma of 2 or more (both
          redox depletions with chroma of 2 or less (both moist and                moist and dry) on 50 percent or more of ped exteriors
          dry) in ped interiors; or                                                or no redox depletions with chroma of 2 or less (both
          b. If peds are absent, chroma of 2 or more (both moist                   moist and dry) in ped interiors; or
          and dry); or                                                             (2) If peds are absent, chroma of 2 or more (both
     2.    Hue of 10YR or yellower and either:                                     moist and dry); or
Alfisols                                                                                                                             43



        b.    Hue of 10YR or yellower and either:                    25 cm thick (cumulative) within 100 cm of the mineral soil
                                                                     surface, that have 25 percent or more (by volume) recognizable
             (1) Both a color value of 3 or more (moist) and         bioturbation, such as filled animal burrows, wormholes, or casts.
             chroma of 3 or more (moist and dry); or                                                             Vermic Natraqualfs
             (2) Chroma of 2 or more (both moist and dry) and no
             redox concentrations.                                   JADC. Other Natraqualfs that have both:
                                   Aeric Umbric Kandiaqualfs
                                                                        1. A glossic horizon or interfingering of albic materials into
                                                                        the natric horizon; and
JAFE. Other Kandiaqualfs that have, in one or more horizons
between the A or Ap horizon and a depth of 75 cm below the              2. An exchangeable sodium percentage of less than 15 and
mineral soil surface, in 50 percent or more of the matrix, one or       less magnesium plus sodium than calcium plus extractable          A
a combination of the following colors:                                  acidity either throughout the upper 15 cm of the natric           L
                                                                                                                                          F
                                                                        horizon or in all horizons within 40 cm of the mineral soil
   1.    Hue of 7.5YR or redder; and
                                                                        surface, whichever is deeper.
        a. If peds are present, chroma of 2 or more (both moist                                            Albic Glossic Natraqualfs
        and dry) on 50 percent or more of ped exteriors or no
        redox depletions with chroma of 2 or less (both moist and    JADD. Other Natraqualfs that have an exchangeable sodium
        dry) in ped interiors; or                                    percentage of less than 15 and less magnesium plus sodium than
        b. If peds are absent, chroma of 2 or more (both moist       calcium plus extractable acidity either throughout the upper 15
        and dry); or                                                 cm of the natric horizon or in all horizons within 40 cm of the
                                                                     mineral soil surface, whichever is deeper.
   2.    Hue of 10YR or yellower and either:                                                                        Albic Natraqualfs
        a. Both a color value of 3 or more (moist) and chroma
        of 3 or more (moist and dry); or                             JADE. Other Natraqualfs that have a glossic horizon or
                                                                     interfingering of albic materials into the natric horizon.
        b. Chroma of 2 or more (both moist and dry) and no                                                         Glossic Natraqualfs
        redox concentrations.
                                          Aeric Kandiaqualfs         JADF. Other Natraqualfs that have a mollic epipedon, or the
                                                                     upper 18 cm of the mineral soil meets the color requirements for
JAFF. Other Kandiaqualfs that have an umbric epipedon,               a mollic epipedon after mixing.
or the upper 18 cm of the mineral soil meets the color                                                           Mollic Natraqualfs
requirements for an umbric epipedon after mixing.
                                         Umbric Kandiaqualfs         JADG. Other Natraqualfs.
                                                                                                                  Typic Natraqualfs
JAFG. Other Kandiaqualfs.
                                               Typic Kandiaqualfs    Plinthaqualfs
Natraqualfs                                                          Key to Subgroups

Key to Subgroups                                                     JABA. All Plinthaqualfs (provisionally).
                                                                                                                Typic Plinthaqualfs
JADA.        Natraqualfs that have one or both of the following:
                                                                     Vermaqualfs
   1. Cracks within 125 cm of the mineral soil surface that are
   5 mm or more wide through a thickness of 30 cm or more            Key to Subgroups
   for some time in normal years and slickensides or wedge-          JAGA. Vermaqualfs that have an exchangeable sodium
   shaped peds in a layer 15 cm or more thick that has its upper     percentage of 7 or more (or a sodium adsorption ratio of 6 or
   boundary within 125 cm of the mineral soil surface; or            more) either or both:
   2. A linear extensibility of 6.0 cm or more between the              1. Throughout the upper 15 cm of the argillic horizon;
   mineral soil surface and either a depth of 100 cm or a densic,       and/or
   lithic, or paralithic contact, whichever is shallower.
                                                Vertic Natraqualfs      2. Throughout all horizons within 40 cm of the mineral soil
                                                                        surface.
JADB. Other Natraqualfs that have one or more layers, at least                                                Natric Vermaqualfs
44                                                                                                                  Keys to Soil Taxonomy



JAGB.      Other Vermaqualfs.                                            and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
                                                Typic Vermaqualfs        more than 1.0.
                                                                                                                   Andic Glossocryalfs
Cryalfs
                                                                         JBBD. Other Glossocryalfs that have, throughout one or more
Key to Great Groups                                                      horizons with a total thickness of 18 cm or more within 75 cm
                                                                         of the mineral soil surface, one or both of the following:
JBA.     Cryalfs that have all of the following:
                                                                            1. More than 35 percent (by volume) fragments coarser
     1. An argillic, kandic, or natric horizon that has its upper
                                                                            than 2.0 mm, of which more than 66 percent is cinders,
     boundary 60 cm or more below both:
                                                                            pumice, and pumicelike fragments; or
        a. The mineral soil surface; and
                                                                            2. A fine-earth fraction containing 30 percent or more
        b. The lower boundary of any surface mantle containing              particles 0.02 to 2.0 mm in diameter; and
        30 percent or more vitric volcanic ash, cinders, or other
        vitric pyroclastic materials; and                                        a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                                                                 volcanic glass; and
     2. A texture class finer than loamy fine sand in one or more
     horizons above the argillic, kandic, or natric horizon; and                 b. [(Al plus 1/2 Fe, percent extracted by ammonium
                                                                                 oxalate) times 60] plus the volcanic glass (percent) is
     3. Either a glossic horizon or interfingering of albic                      equal to 30 or more.
     materials into the argillic, kandic, or natric horizon.                                                       Vitrandic Glossocryalfs
                                                    Palecryalfs, p. 47
                                                                         JBBE. Other Glossocryalfs that have, in one or more
JBB.     Other Cryalfs that have a glossic horizon.                      subhorizons within the upper 25 cm of the argillic, kandic, or
                                              Glossocryalfs, p. 44       natric horizon, redox depletions with chroma of 2 or less and
                                                                         also aquic conditions for some time in normal years (or artificial
JBC. Other Cryalfs.                                                      drainage).
                                                Haplocryalfs, p. 45                                                 Aquic Glossocryalfs

Glossocryalfs                                                            JBBF. Other Glossocryalfs that are saturated with water in
                                                                         one or more layers within 100 cm of the mineral soil surface in
Key to Subgroups
                                                                         normal years for either or both:
JBBA. Glossocryalfs that have a lithic contact within 50 cm of
                                                                            1.    20 or more consecutive days; or
the mineral soil surface.
                                         Lithic Glossocryalfs               2.    30 or more cumulative days.
                                                                                                                  Oxyaquic Glossocryalfs
JBBB. Other Glossocryalfs that have one or both of the
following:                                                               JBBG.      Other Glossocryalfs that have fragic soil properties:
     1. Cracks within 125 cm of the mineral soil surface that are           1. In 30 percent or more of the volume of a layer 15 cm or
     5 mm or more wide through a thickness of 30 cm or more                 more thick that has its upper boundary within 100 cm of the
     for some time in normal years and slickensides or wedge-               mineral soil surface; or
     shaped peds in a layer 15 cm or more thick that has its upper
                                                                            2. In 60 percent or more of the volume of a layer 15 cm or
     boundary within 125 cm of the mineral soil surface; or
                                                                            more thick.
     2. A linear extensibility of 6.0 cm or more between the                                                     Fragic Glossocryalfs
     mineral soil surface and either a depth of 100 cm or a densic,
     lithic, or paralithic contact, whichever is shallower.              JBBH. Other Glossocryalfs that have all of the following:
                                                Vertic Glossocryalfs
                                                                            1. A xeric soil moisture regime; and
JBBC. Other Glossocryalfs that have, throughout one or more                 2. A color value, moist, of 3 or less and a color value, dry,
horizons with a total thickness of 18 cm or more within 75 cm               of 5 or less (crushed and smoothed sample) either throughout
of the mineral soil surface, a fine-earth fraction with both a bulk         the upper 18 cm of the mineral soil (unmixed) or between the
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,           mineral soil surface and a depth of 18 cm after mixing; and
Alfisols                                                                                                                              45



   3. A base saturation (by NH4OAc) of 50 percent or more             smoothed sample) either throughout the upper 18 cm of the
   in all parts from the mineral soil surface to a depth of 180       mineral soil (unmixed) or between the mineral soil surface and a
   cm or to a densic, lithic, or paralithic contact, whichever is     depth of 18 cm after mixing.
   shallower.                                                                                                 Umbric Glossocryalfs
                                             Xerollic Glossocryalfs
                                                                      JBBO. Other Glossocryalfs that have a base saturation (by
JBBI.      Other Glossocryalfs that have both:                        NH4OAc) of 50 percent or more in all parts from the mineral
                                                                      soil surface to a depth of 180 cm or to a densic, lithic, or
   1. A xeric soil moisture regime; and
                                                                      paralithic contact, whichever is shallower.
   2. A color value, moist, of 3 or less and a color value, dry,                                                  Eutric Glossocryalfs
   of 5 or less (crushed and smoothed sample) either throughout                                                                             A
   the upper 18 cm of the mineral soil (unmixed) or between the       JBBP.     Other Glossocryalfs.                                        L
                                                                                                                                            F
   mineral soil surface and a depth of 18 cm after mixing.                                                         Typic Glossocryalfs
                                   Umbric Xeric Glossocryalfs
                                                                      Haplocryalfs
JBBJ. Other Glossocryalfs that meet all of the following:
                                                                      Key to Subgroups
   1. Are dry in some part of the moisture control section for
   45 or more days (cumulative) in normal years; and                  JBCA. Haplocryalfs that have a lithic contact within 50 cm of
                                                                      the mineral soil surface.
   2. Have a color value, moist, of 3 or less and a color value,                                               Lithic Haplocryalfs
   dry, of 5 or less (crushed and smoothed sample) either
   throughout the upper 18 cm of the mineral soil (unmixed) or        JBCB. Other Haplocryalfs that have one or both of the
   between the mineral soil surface and a depth of 18 cm after        following:
   mixing; and
                                                                         1. Cracks within 125 cm of the mineral soil surface that are
   3. Have a base saturation (by NH4OAc) of 50 percent or
                                                                         5 mm or more wide through a thickness of 30 cm or more
   more in all parts from the mineral soil surface to a depth of
                                                                         for some time in normal years and slickensides or wedge-
   180 cm or to a densic, lithic, or paralithic contact, whichever
                                                                         shaped peds in a layer 15 cm or more thick that has its upper
   is shallower.
                                                                         boundary within 125 cm of the mineral soil surface; or
                                            Ustollic Glossocryalfs
                                                                         2. A linear extensibility of 6.0 cm or more between the
JBBK. Other Glossocryalfs that have a xeric soil moisture                mineral soil surface and either a depth of 100 cm or a densic,
regime.                                                                  lithic, or paralithic contact, whichever is shallower.
                                        Xeric Glossocryalfs                                                          Vertic Haplocryalfs

JBBL. Other Glossocryalfs that are dry in some part of the            JBCC. Other Haplocryalfs that have, throughout one or more
moisture control section for 45 or more days (cumulative) in          horizons with a total thickness of 18 cm or more within 75 cm
normal years.                                                         of the mineral soil surface, a fine-earth fraction with both a bulk
                                            Ustic Glossocryalfs       density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
                                                                      and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
JBBM.       Other Glossocryalfs that have both:                       more than 1.0.
   1. A color value, moist, of 3 or less and a color value, dry,                                                     Andic Haplocryalfs
   of 5 or less (crushed and smoothed sample) either throughout
   the upper 18 cm of the mineral soil (unmixed) or between           JBCD. Other Haplocryalfs that have, throughout one or more
   the mineral soil surface and a depth of 18 cm after mixing;        horizons with a total thickness of 18 cm or more within 75 cm
   and                                                                of the mineral soil surface, one or both of the following:

   2. A base saturation (by NH4OAc) of 50 percent or more                1. More than 35 percent (by volume) fragments coarser
   in all parts from the mineral soil surface to a depth of 180          than 2.0 mm, of which more than 66 percent is cinders,
   cm or to a densic, lithic, or paralithic contact, whichever is        pumice, and pumicelike fragments; or
   shallower.                                                            2. A fine-earth fraction containing 30 percent or more
                                              Mollic Glossocryalfs       particles 0.02 to 2.0 mm in diameter; and
JBBN. Other Glossocryalfs that have a color value, moist,                     a. In the 0.02 to 2.0 mm fraction, 5 percent or more
of 3 or less and a color value, dry, of 5 or less (crushed and                volcanic glass; and
46                                                                                                               Keys to Soil Taxonomy



          b. [(Al plus 1/2 Fe, percent extracted by ammonium            JBCJ.   Other Haplocryalfs that have all of the following:
          oxalate) times 60] plus the volcanic glass (percent) is
                                                                          1. A xeric soil moisture regime; and
          equal to 30 or more.
                                             Vitrandic Haplocryalfs       2. A color value, moist, of 3 or less and a color value, dry,
                                                                          of 5 or less (crushed and smoothed sample) either throughout
JBCE. Other Haplocryalfs that have, in one or more horizons               the upper 18 cm of the mineral soil (unmixed) or between the
within 75 cm of the mineral soil surface, redox depletions with           mineral soil surface and a depth of 18 cm after mixing; and
chroma of 2 or less and also aquic conditions for some time in
                                                                          3. A base saturation (by NH4OAc) of 50 percent or more
normal years (or artificial drainage).
                                                                          in all parts from the mineral soil surface to a depth of 180
                                            Aquic Haplocryalfs
                                                                          cm or to a densic, lithic, or paralithic contact, whichever is
                                                                          shallower.
JBCF. Other Haplocryalfs that are saturated with water in
                                                                                                                    Xerollic Haplocryalfs
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:
                                                                        JBCK.   Other Haplocryalfs that have both:
     1.    20 or more consecutive days; or
                                                                          1. A xeric soil moisture regime; and
     2.    30 or more cumulative days.
                                                                          2. A color value, moist, of 3 or less and a color value, dry,
                                               Oxyaquic Haplocryalfs
                                                                          of 5 or less (crushed and smoothed sample) either throughout
                                                                          the upper 18 cm of the mineral soil (unmixed) or between the
JBCG. Other Haplocryalfs that have an argillic horizon that
                                                                          mineral soil surface and a depth of 18 cm after mixing.
meets one of the following:
                                                                                                           Umbric Xeric Haplocryalfs
     1.    Consists entirely of lamellae; or
                                                                        JBCL.   Other Haplocryalfs that meet all of the following:
     2. Is a combination of two or more lamellae and one or
     more subhorizons with a thickness of 7.5 to 20 cm, each              1. Are dry in some part of the moisture control section for
     layer with an overlying eluvial horizon; or                          45 or more days (cumulative) in normal years; and
     3. Consists of one or more subhorizons that are more than            2. Have a color value, moist, of 3 or less and a color value,
     20 cm thick, each with an overlying eluvial horizon, and             dry, of 5 or less (crushed and smoothed sample) either
     above these horizons there are either:                               throughout the upper 18 cm of the mineral soil (unmixed) or
                                                                          between the mineral soil surface and a depth of 18 cm after
          a. Two or more lamellae with a combined thickness of
                                                                          mixing; and
          5 cm or more (that may or may not be part of the argillic
          horizon); or                                                    3. Have a base saturation (by NH4OAc) of 50 percent or
                                                                          more in all parts from the mineral soil surface to a depth of
          b. A combination of lamellae (that may or may not be
                                                                          180 cm or to a densic, lithic, or paralithic contact, whichever
          part of the argillic horizon) and one or more parts of the
                                                                          is shallower.
          argillic horizon 7.5 to 20 cm thick, each with an overlying
                                                                                                                    Ustollic Haplocryalfs
          eluvial horizon.
                                              Lamellic Haplocryalfs
                                                                        JBCM. Other Haplocryalfs that have a xeric soil moisture
                                                                        regime.
JBCH. Other Haplocryalfs that have a sandy or sandy-skeletal
                                                                                                                Xeric Haplocryalfs
particle-size class throughout the upper 75 cm of the argillic,
kandic, or natric horizon or throughout the entire argillic,
                                                                        JBCN. Other Haplocryalfs that are dry in some part of the
kandic, or natric horizon if it is less than 75 cm thick.
                                                                        moisture control section for 45 or more days (cumulative) in
                                         Psammentic Haplocryalfs
                                                                        normal years.
                                                                                                                    Ustic Haplocryalfs
JBCI.       Other Haplocryalfs that:
     1. Have an argillic, kandic, or natric horizon that is 35 cm       JBCO. Other Haplocryalfs that have both:
     or less thick; and
                                                                          1. A color value, moist, of 3 or less and a color value, dry,
     2. Do not have a densic, lithic, or paralithic contact within        of 5 or less (crushed and smoothed sample) either throughout
     100 cm of the mineral soil surface.                                  the upper 18 cm of the mineral soil (unmixed) or between the
                                            Inceptic Haplocryalfs         mineral soil surface and a depth of 18 cm after mixing; and
Alfisols                                                                                                                           47



   2. A base saturation (by NH4OAc) of 50 percent or more           chroma of 2 or less and also aquic conditions for some time in
   in all parts from the mineral soil surface to a depth of 180     normal years (or artificial drainage).
   cm or to a densic, lithic, or paralithic contact, whichever is                                                 Aquic Palecryalfs
   shallower.
                                              Mollic Haplocryalfs   JBAD. Other Palecryalfs that are saturated with water in one
                                                                    or more layers within 100 cm of the mineral soil surface in
JBCP. Other Haplocryalfs that have a color value, moist,            normal years for either or both:
of 3 or less and a color value, dry, of 5 or less (crushed and
                                                                       1.   20 or more consecutive days; or
smoothed sample) either throughout the upper 18 cm of the
mineral soil (unmixed) or between the mineral soil surface and a       2.   30 or more cumulative days.
depth of 18 cm after mixing.                                                                                  Oxyaquic Palecryalfs       A
                                             Umbric Haplocryalfs                                                                         L
                                                                                                                                         F
                                                                    JBAE. Other Palecryalfs that have a xeric soil moisture
JBCQ. Other Haplocryalfs that have a base saturation (by            regime.
NH4OAc) of 50 percent or more in all parts from the mineral                                                     Xeric Palecryalfs
soil surface to a depth of 180 cm or to a densic, lithic, or
paralithic contact, whichever is shallower.                         JBAF. Other Palecryalfs that are dry in some part of the
                                            Eutric Haplocryalfs     moisture control section for 45 or more days (cumulative) in
                                                                    normal years.
JBCR.      Other Haplocryalfs.                                                                                     Ustic Palecryalfs
                                            Typic Haplocryalfs
                                                                    JBAG. Other Palecryalfs that have both:
Palecryalfs                                                            1. A color value, moist, of 3 or less and a color value, dry,
Key to Subgroups                                                       of 5 or less (crushed and smoothed sample) either throughout
                                                                       the upper 18 cm of the mineral soil (unmixed) or between the
JBAA. Palecryalfs that have, throughout one or more horizons           mineral soil surface and a depth of 18 cm after mixing; and
with a total thickness of 18 cm or more within 75 cm of the
mineral soil surface, a fine-earth fraction with both a bulk           2. A base saturation (by NH4OAc) of 50 percent or more
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,      in all parts from the mineral soil surface to a depth of 180
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling          cm or to a densic, lithic, or paralithic contact, whichever is
more than 1.0.                                                         shallower.
                                                Andic Palecryalfs                                                   Mollic Palecryalfs

JBAB. Other Palecryalfs that have, throughout one or more           JBAH. Other Palecryalfs that have a color value, moist, of 3 or
horizons with a total thickness of 18 cm or more within 75 cm       less and a color value, dry, of 5 or less (crushed and smoothed
of the mineral soil surface, one or both of the following:          sample) either throughout the upper 18 cm of the mineral soil
                                                                    (unmixed) or between the mineral soil surface and a depth of 18
   1. More than 35 percent (by volume) fragments coarser            cm after mixing.
   than 2.0 mm, of which more than 66 percent is cinders,                                                          Umbric Palecryalfs
   pumice, and pumicelike fragments; or
   2. A fine-earth fraction containing 30 percent or more           JBAI.    Other Palecryalfs.
   particles 0.02 to 2.0 mm in diameter; and                                                                       Typic Palecryalfs

      a. In the 0.02 to 2.0 mm fraction, 5 percent or more
      volcanic glass; and                                           Udalfs
      b. [(Al plus 1/2 Fe, percent extracted by ammonium            Key to Great Groups
      oxalate) times 60] plus the volcanic glass (percent) is       JEA. Udalfs that have a natric horizon.
      equal to 30 or more.                                                                                         Natrudalfs, p. 56
                                           Vitrandic Palecryalfs
                                                                    JEB.    Other Udalfs that have both:
JBAC. Other Palecryalfs that have, in one or more horizons
within 100 cm of the mineral soil surface, redox depletions with       1. A glossic horizon; and
48                                                                                                                   Keys to Soil Taxonomy



     2. In the argillic or kandic horizon, discrete nodules, 2.5 to             b. Have 5 percent or more (by volume) skeletans on
     30 cm in diameter, that:                                                   faces of peds in the layer that has a 20 percent lower clay
                                                                                content and, below that layer, a clay increase of 3 percent
          a. Are enriched with iron and extremely weakly
                                                                                or more (absolute) in the fine-earth fraction; and
          cemented to indurated; and
                                                                           3. Have an argillic horizon with one or more of the
          b. Have exteriors with either a redder hue or a higher
                                                                           following:
          chroma than the interiors.
                                                  Ferrudalfs, p. 49             a. In 50 percent or more of the matrix of one or more
                                                                                subhorizons in its lower one-half, hue of 7.5YR or redder
JEC. Other Udalfs that have both:                                               and chroma of 5 or more; or
     1. A glossic horizon; and                                                  b. In 50 percent or more of the matrix of horizons that
                                                                                total more than one-half the total thickness, hue of 2.5YR
     2. A fragipan within 100 cm of the mineral soil surface.
                                                                                or redder, value, moist, of 3 or less, and value, dry, of 4 or
                                          Fraglossudalfs, p. 49
                                                                                less; or
JED. Other Udalfs that have a fragipan within 100 cm of the                     c. Many coarse redox concentrations with hue of 5YR
mineral soil surface.                                                           or redder or chroma of 6 or more, or both, in one or more
                                           Fragiudalfs, p. 49                   subhorizons; or
                                                                           4. Have a frigid soil temperature regime and all of the
JEE.       Other Udalfs that meet all of the following:
                                                                           following:
     1. Do not have a densic, lithic, paralithic, or petroferric
                                                                                a. An argillic horizon that has its upper boundary 60 cm
     contact within 150 cm of the mineral soil surface; and
                                                                                or more below both:
     2.    Have a kandic horizon; and
                                                                                   (1) The mineral soil surface; and
     3. Within 150 cm of the mineral soil surface, either:
                                                                                   (2) The lower boundary of any surface mantle
          a. Do not have a clay decrease with increasing depth                     containing 30 percent or more vitric volcanic ash,
          of 20 percent or more (relative) from the maximum clay                   cinders, or other vitric pyroclastic materials; and
          content [Clay is measured noncarbonate clay or is based
                                                                                b. A texture class finer than loamy fine sand in one or
          on the following formula: Clay % = 2.5(% water retained
                                                                                more horizons above the argillic horizon; and
          at 1500 kPa tension - % organic carbon), whichever value
          is greater, but no more than 100]; or                                 c. Either a glossic horizon or interfingering of albic
                                                                                materials into the argillic horizon.
          b. Have 5 percent or more (by volume) skeletans on
                                                                                                                         Paleudalfs, p. 57
          faces of peds in the layer that has a 20 percent lower clay
          content and, below that layer, a clay increase of 3 percent
                                                                        JEH. Other Udalfs that have, in all subhorizons in the upper
          or more (absolute) in the fine-earth fraction.
                                                                        100 cm of the argillic horizon or throughout the entire argillic
                                                   Kandiudalfs, p. 55
                                                                        horizon if less than 100 cm thick, more than 50 percent colors
                                                                        that have all of the following:
JEF. Other Udalfs that have a kandic horizon.
                                        Kanhapludalfs, p. 56               1.    Hue of 2.5YR or redder; and
                                                                           2. Value, moist, of 3 or less; and
JEG. Other Udalfs that:
                                                                           3. Dry value no more than 1 unit higher than the moist
     1. Do not have a densic, lithic, or paralithic contact within         value.
     150 cm of the mineral soil surface; and                                                                        Rhodudalfs, p. 59
     2. Within 150 cm of the mineral soil surface, either:
                                                                        JEI.    Other Udalfs that have a glossic horizon.
          a. Do not have a clay decrease with increasing depth                                                         Glossudalfs, p. 49
          of 20 percent or more (relative) from the maximum clay
          content [Clay is measured noncarbonate clay or is based       JEJ.    Other Udalfs.
          on the following formula: Clay % = 2.5(% water retained                                                          Hapludalfs, p. 51
          at 1500 kPa tension - % organic carbon), whichever value
          is greater, but no more than 100]; or
Alfisols                                                                                                                            49



Ferrudalfs                                                          JEDE. Other Fragiudalfs.
                                                                                                                   Typic Fragiudalfs
Key to Subgroups
JEBA. Ferrudalfs that have, in one or more horizons within          Fraglossudalfs
60 cm of the mineral soil surface, redox depletions with chroma
                                                                    Key to Subgroups
of 2 or less and also aquic conditions for some time in normal
years (or artificial drainage).                                     JECA. Fraglossudalfs that have, throughout one or more
                                               Aquic Ferrudalfs     horizons with a total thickness of 18 cm or more within 75 cm
                                                                    of the mineral soil surface, a fine-earth fraction with both a bulk
JEBB. Other Ferrudalfs.                                             density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
                                               Typic Ferrudalfs     and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling         A
                                                                    more than 1.0.                                                        L
                                                                                                                                          F
Fragiudalfs                                                                                                      Andic Fraglossudalfs
Key to Subgroups                                                    JECB. Other Fraglossudalfs that have, throughout one or more
JEDA. Fragiudalfs that have, throughout one or more horizons        horizons with a total thickness of 18 cm or more within 75 cm
with a total thickness of 18 cm or more within 75 cm of the         of the mineral soil surface, one or both of the following:
mineral soil surface, a fine-earth fraction with both a bulk           1. More than 35 percent (by volume) fragments coarser
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,      than 2.0 mm, of which more than 66 percent is cinders,
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling          pumice, and pumicelike fragments; or
more than 1.0.
                                               Andic Fragiudalfs       2. A fine-earth fraction containing 30 percent or more
                                                                       particles 0.02 to 2.0 mm in diameter; and
JEDB. Other Fragiudalfs that have, throughout one or more                   a. In the 0.02 to 2.0 mm fraction, 5 percent or more
horizons with a total thickness of 18 cm or more within 75 cm               volcanic glass; and
of the mineral soil surface, one or both of the following:
                                                                            b. [(Al plus 1/2 Fe, percent extracted by ammonium
   1. More than 35 percent (by volume) fragments coarser                    oxalate) times 60] plus the volcanic glass (percent) is
   than 2.0 mm, of which more than 66 percent is cinders,                   equal to 30 or more.
   pumice, and pumicelike fragments; or                                                                      Vitrandic Fraglossudalfs
   2. A fine-earth fraction containing 30 percent or more
   particles 0.02 to 2.0 mm in diameter; and                        JECC. Other Fraglossudalfs that have, in one or more
                                                                    subhorizons within the upper 25 cm of the argillic or kandic
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more        horizon, redox depletions with chroma of 2 or less and also
        volcanic glass; and                                         aquic conditions for some time in normal years (or artificial
        b. [(Al plus 1/2 Fe, percent extracted by ammonium          drainage).
        oxalate) times 60] plus the volcanic glass (percent) is                                              Aquic Fraglossudalfs
        equal to 30 or more.
                                            Vitrandic Fragiudalfs   JECD. Other Fraglossudalfs that are saturated with water in
                                                                    one or more layers above the fragipan in normal years for either
JEDC. Other Fragiudalfs that have, in one or more horizons          or both:
within 40 cm of the mineral soil surface, redox depletions with        1.    20 or more consecutive days; or
chroma of 2 or less and also aquic conditions for some time in
normal years (or artificial drainage).                                 2.    30 or more cumulative days.
                                              Aquic Fragiudalfs                                             Oxyaquic Fraglossudalfs

JEDD. Other Fragiudalfs that are saturated with water in one        JECE. Other Fraglossudalfs.
or more layers above the fragipan in normal years for either or                                                Typic Fraglossudalfs
both:
   1.    20 or more consecutive days; or
                                                                    Glossudalfs
                                                                    Key to Subgroups
   2.    30 or more cumulative days.
                                           Oxyaquic Fragiudalfs     JEIA.     Glossudalfs that have both:
50                                                                                                                    Keys to Soil Taxonomy



     1.    One or both of the following:                                      2. A linear extensibility of 6.0 cm or more between the
                                                                              mineral soil surface and either a depth of 100 cm or a densic,
          a. Cracks within 125 cm of the mineral soil surface that
                                                                              lithic, or paralithic contact, whichever is shallower.
          are 5 mm or more wide through a thickness of 30 cm or
                                                                                                                           Vertic Glossudalfs
          more for some time in normal years and slickensides or
          wedge-shaped peds in a layer 15 cm or more thick that
                                                                           JEID.     Other Glossudalfs that have both:
          has its upper boundary within 125 cm of the mineral soil
          surface; or                                                         1. In one or more subhorizons within the upper 25 cm of
                                                                              the argillic horizon, redox depletions with chroma of 2 or
          b. A linear extensibility of 6.0 cm or more between
                                                                              less and also aquic conditions for some time in normal years
          the mineral soil surface and either a depth of 100 cm
                                                                              (or artificial drainage); and
          or a densic, lithic, or paralithic contact, whichever is
          shallower; and                                                      2. Throughout one or more horizons with a total thickness
                                                                              of 18 cm or more within 75 cm of the mineral soil surface,
     2. Redox depletions with chroma of 2 or less in layers
                                                                              one or more of the following:
     that also have aquic conditions in normal years (or artificial
     drainage) either:                                                             a. A fine-earth fraction with both a bulk density of 1.0
                                                                                   g/cm3 or less, measured at 33 kPa water retention, and Al
          a. Within the upper 25 cm of the argillic horizon if
                                                                                   plus 1/2 Fe percentages (by ammonium oxalate) totaling
          its upper boundary is within 50 cm of the mineral soil
                                                                                   more than 1.0; or
          surface; or
                                                                                   b. More than 35 percent (by volume) fragments coarser
          b. Within 75 cm of the mineral soil surface if the upper
                                                                                   than 2.0 mm, of which more than 66 percent is cinders,
          boundary of the argillic horizon is 50 cm or more below
                                                                                   pumice, and pumicelike fragments; or
          the mineral soil surface.
                                               Aquertic Glossudalfs                c. A fine-earth fraction containing 30 percent or more
                                                                                   particles 0.02 to 2.0 mm in diameter; and
JEIB. Other Glossudalfs that have both:
                                                                                     (1) In the 0.02 to 2.0 mm fraction, 5 percent or more
     1. Saturation with water in one or more layers within 100                       volcanic glass; and
     cm of the mineral soil surface in normal years for either or
                                                                                     (2) [(Al plus 1/2 Fe, percent extracted by ammonium
     both:
                                                                                     oxalate) times 60] plus the volcanic glass (percent) is
          a.   20 or more consecutive days; or                                       equal to 30 or more.
                                                                                                                      Aquandic Glossudalfs
          b.   30 or more cumulative days; and
     2.    One or both of the following:                                   JEIE. Other Glossudalfs that have, throughout one or more
                                                                           horizons with a total thickness of 18 cm or more within 75 cm
          a. Cracks within 125 cm of the mineral soil surface that
                                                                           of the mineral soil surface, a fine-earth fraction with both a bulk
          are 5 mm or more wide through a thickness of 30 cm or
                                                                           density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
          more for some time in normal years and slickensides or
                                                                           and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
          wedge-shaped peds in a layer 15 cm or more thick that
                                                                           more than 1.0.
          has its upper boundary within 125 cm of the mineral soil
                                                                                                                           Andic Glossudalfs
          surface; or
          b. A linear extensibility of 6.0 cm or more between the          JEIF. Other Glossudalfs that have, throughout one or more
          mineral soil surface and either a depth of 100 cm or a           horizons with a total thickness of 18 cm or more within 75 cm
          densic, lithic, or paralithic contact, whichever is shallower.   of the mineral soil surface, one or both of the following:
                                         Oxyaquic Vertic Glossudalfs
                                                                              1. More than 35 percent (by volume) fragments coarser
                                                                              than 2.0 mm, of which more than 66 percent is cinders,
JEIC. Other Glossudalfs that have one or both of the
                                                                              pumice, and pumicelike fragments; or
following:
                                                                              2. A fine-earth fraction containing 30 percent or more
     1. Cracks within 125 cm of the mineral soil surface that are
                                                                              particles 0.02 to 2.0 mm in diameter; and
     5 mm or more wide through a thickness of 30 cm or more
     for some time in normal years and slickensides or wedge-                      a. In the 0.02 to 2.0 mm fraction, 5 percent or more
     shaped peds in a layer 15 cm or more thick that has its upper                 volcanic glass; and
     boundary within 125 cm of the mineral soil surface; or
Alfisols                                                                                                                               51



        b. [(Al plus 1/2 Fe, percent extracted by ammonium             to the top of the argillic horizon at a depth of 50 cm or more
        oxalate) times 60] plus the volcanic glass (percent) is        below the mineral soil surface.
        equal to 30 or more.                                                                            Arenic Oxyaquic Glossudalfs
                                            Vitrandic Glossudalfs
                                                                    JEIK. Other Glossudalfs that are saturated with water in one
JEIG.        Other Glossudalfs that have both:                      or more layers within 100 cm of the mineral soil surface in
                                                                    normal years for either or both:
   1.    Fragic soil properties:
                                                                       1.    20 or more consecutive days; or
        a. In 30 percent or more of the volume of a layer 15 cm
        or more thick that has its upper boundary within 100 cm        2.    30 or more cumulative days.
        of the mineral soil surface; or                                                                          Oxyaquic Glossudalfs       A
                                                                                                                                            L
        b. In 60 percent or more of the volume of a layer 15 cm                                                                             F
                                                                    JEIL. Other Glossudalfs that have fragic soil properties:
        or more thick; and
                                                                       1. In 30 percent or more of the volume of a layer 15 cm or
   2. Redox depletions with chroma of 2 or less in layers
                                                                       more thick that has its upper boundary within 100 cm of the
   that also have aquic conditions in normal years (or artificial
                                                                       mineral soil surface; or
   drainage) either:
                                                                       2. In 60 percent or more of the volume of a layer 15 cm or
        a. Within the upper 25 cm of the argillic horizon if
                                                                       more thick.
        its upper boundary is within 50 cm of the mineral soil
                                                                                                              Fragic Glossudalfs
        surface; or
        b. Within 75 cm of the mineral soil surface if the upper    JEIM. Other Glossudalfs that meet sandy or sandy-skeletal
        boundary of the argillic horizon is 50 cm or more below     particle-size class criteria throughout a layer extending from the
        the mineral soil surface.                                   mineral soil surface to the top of an argillic horizon at a depth of
                                           Fragiaquic Glossudalfs   50 cm or more below the mineral soil surface.
                                                                                                                   Arenic Glossudalfs
JEIH.        Other Glossudalfs that:
                                                                    JEIN. Other Glossudalfs that have a glossic horizon less than
   1. In one or more subhorizons within 75 cm of the mineral
                                                                    50 cm in total thickness.
   soil surface, have redox depletions with chroma of 2 or less
                                                                                                              Haplic Glossudalfs
   and also aquic conditions for some time in normal years (or
   artificial drainage); and
                                                                    JEIO. Other Glossudalfs.
   2. Meet sandy or sandy-skeletal particle-size class criteria                                                      Typic Glossudalfs
   throughout a layer extending from the mineral soil surface
   to the top of the argillic horizon at a depth of 50 cm or more   Hapludalfs
   below the mineral soil surface.
                                                                    Key to Subgroups
                                        Aquic Arenic Glossudalfs
                                                                    JEJA. Hapludalfs that have a lithic contact within 50 cm of the
JEII. Other Glossudalfs that have, in one or more subhorizons       mineral soil surface.
within the upper 25 cm of the argillic horizon, redox depletions                                                Lithic Hapludalfs
with chroma of 2 or less and also aquic conditions for some
time in normal years (or artificial drainage).                      JEJB.     Other Hapludalfs that have all of the following:
                                               Aquic Glossudalfs
                                                                       1.    One or both of the following:
JEIJ.    Other Glossudalfs that:                                            a. Cracks within 125 cm of the mineral soil surface that
                                                                            are 5 mm or more wide through a thickness of 30 cm or
   1. Are saturated with water in one or more layers within                 more for some time in normal years and slickensides or
   100 cm of the mineral soil surface in normal years for either            wedge-shaped peds in a layer 15 cm or more thick that
   or both:                                                                 has its upper boundary within 125 cm of the mineral soil
                                                                            surface; or
        a.    20 or more consecutive days; or
                                                                            b. A linear extensibility of 6.0 cm or more between
        b.    30 or more cumulative days; and
                                                                            the mineral soil surface and either a depth of 100 cm
   2. Meet sandy or sandy-skeletal particle-size class criteria             or a densic, lithic, or paralithic contact, whichever is
   throughout a layer extending from the mineral soil surface               shallower; and
52                                                                                                                    Keys to Soil Taxonomy



     2. Redox depletions with chroma of 2 or less in layers                   b. 30 or more cumulative days; and
     that also have aquic conditions in normal years (or artificial
                                                                         2.    One or both of the following:
     drainage) either:
                                                                              a. Cracks within 125 cm of the mineral soil surface that
          a. Within the upper 25 cm of the argillic horizon if                are 5 mm or more wide through a thickness of 30 cm or
          its upper boundary is within 50 cm of the mineral soil              more for some time in normal years and slickensides or
          surface; or                                                         wedge-shaped peds in a layer 15 cm or more thick that
          b. Within 75 cm of the mineral soil surface if the upper            has its upper boundary within 125 cm of the mineral soil
          boundary of the argillic horizon is 50 cm or more below             surface; or
          the mineral soil surface; and                                       b. A linear extensibility of 6.0 cm or more between the
     3. An Ap horizon or materials between the mineral soil                   mineral soil surface and either a depth of 100 cm or a
     surface and a depth of 18 cm that, after mixing, have one or             densic, lithic, or paralithic contact, whichever is shallower.
     more of the following:                                                                                   Oxyaquic Vertic Hapludalfs

          a. A color value, moist, of 4 or more; or                   JEJE.        Other Hapludalfs that have both:
          b. A color value, dry, of 6 or more; or                        1.    One or both of the following:
          c.    Chroma of 4 or more.                                          a. Cracks within 125 cm of the mineral soil surface that
                                       Aquertic Chromic Hapludalfs            are 5 mm or more wide through a thickness of 30 cm or
                                                                              more for some time in normal years and slickensides or
                                                                              wedge-shaped peds in a layer 15 cm or more thick that
JEJC. Other Hapludalfs that have both:
                                                                              has its upper boundary within 125 cm of the mineral soil
     1.    One or both of the following:                                      surface; or
          a. Cracks within 125 cm of the mineral soil surface that            b. A linear extensibility of 6.0 cm or more between
          are 5 mm or more wide through a thickness of 30 cm or               the mineral soil surface and either a depth of 100 cm
          more for some time in normal years and slickensides or              or a densic, lithic, or paralithic contact, whichever is
          wedge-shaped peds in a layer 15 cm or more thick that               shallower; and
          has its upper boundary within 125 cm of the mineral soil
                                                                         2. An Ap horizon or materials between the mineral soil
          surface; or
                                                                         surface and a depth of 18 cm that, after mixing, have one or
          b. A linear extensibility of 6.0 cm or more between            more of the following:
          the mineral soil surface and either a depth of 100 cm
                                                                              a. A color value, moist, of 4 or more; or
          or a densic, lithic, or paralithic contact, whichever is
          shallower; and                                                      b. A color value, dry, of 6 or more; or
     2. Redox depletions with chroma of 2 or less in layers                   c.     Chroma of 4 or more.
     that also have aquic conditions in normal years (or artificial                                           Chromic Vertic Hapludalfs
     drainage) either:
                                                                      JEJF.    Other Hapludalfs that have one or both of the following:
          a. Within the upper 25 cm of the argillic horizon if
          its upper boundary is within 50 cm of the mineral soil         1. Cracks within 125 cm of the mineral soil surface that are
          surface; or                                                    5 mm or more wide through a thickness of 30 cm or more
                                                                         for some time in normal years and slickensides or wedge-
          b. Within 75 cm of the mineral soil surface if the upper
                                                                         shaped peds in a layer 15 cm or more thick that has its upper
          boundary of the argillic horizon is 50 cm or more below
                                                                         boundary within 125 cm of the mineral soil surface; or
          the mineral soil surface.
                                                Aquertic Hapludalfs      2. A linear extensibility of 6.0 cm or more between the
                                                                         mineral soil surface and either a depth of 100 cm or a densic,
JEJD.          Other Hapludalfs that have both:                          lithic, or paralithic contact, whichever is shallower.
                                                                                                                       Vertic Hapludalfs
     1. Saturation with water in one or more layers within 100
     cm of the mineral soil surface in normal years for either or
                                                                      JEJG. Other Hapludalfs that have, throughout one or more
     both:
                                                                      horizons with a total thickness of 18 cm or more within 75 cm
          a.    20 or more consecutive days; or                       of the mineral soil surface, a fine-earth fraction with both a bulk
Alfisols                                                                                                                             53



density of 1.0 g/cm3 or less, measured at 33 kPa water retention,           a. 20 or more consecutive days; or
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
                                                                            b.     30 or more cumulative days.
more than 1.0.
                                                                                                          Fragic Oxyaquic Hapludalfs
                                              Andic Hapludalfs
                                                                    JEJK.        Other Hapludalfs that:
JEJH. Other Hapludalfs that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm         1. In one or more horizons within 75 cm of the mineral
of the mineral soil surface, one or both of the following:            soil surface, have redox depletions with chroma of 2 or less
                                                                      and also aquic conditions for some time in normal years (or
   1. More than 35 percent (by volume) fragments coarser
                                                                      artificial drainage); and
   than 2.0 mm, of which more than 66 percent is cinders,
   pumice, and pumicelike fragments; or                               2. Meet sandy or sandy-skeletal particle-size class criteria        A
                                                                                                                                          L
                                                                      throughout a layer extending from the mineral soil surface to       F
   2. A fine-earth fraction containing 30 percent or more
                                                                      the top of an argillic horizon at a depth of 50 cm or more.
   particles 0.02 to 2.0 mm in diameter; and
                                                                                                           Aquic Arenic Hapludalfs
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more
        volcanic glass; and                                         JEJL.        Other Hapludalfs that:
        b. [(Al plus /2 Fe, percent extracted by ammonium
                      1

        oxalate) times 60] plus the volcanic glass (percent) is       1. Are saturated with water in one or more layers within
                                                                      100 cm of the mineral soil surface in normal years for either
        equal to 30 or more.
                                                                      or both:
                                             Vitrandic Hapludalfs
                                                                            a.     20 or more consecutive days; or
JEJI.    Other Hapludalfs that have both:
                                                                            b.     30 or more cumulative days; and
   1.    Fragic soil properties:
                                                                      2. Meet sandy or sandy-skeletal particle-size class criteria
        a. In 30 percent or more of the volume of a layer 15 cm       throughout a layer extending from the mineral soil surface
        or more thick that has its upper boundary within 100 cm       to the top of the argillic horizon at a depth of 50 cm or more
        of the mineral soil surface; or                               below the mineral soil surface.
        b. In 60 percent or more of the volume of a layer 15 cm                                        Arenic Oxyaquic Hapludalfs
        or more thick; and
                                                                    JEJM.        Other Hapludalfs that have anthraquic conditions.
   2. Redox depletions with chroma of 2 or less in layers                                                      Anthraquic Hapludalfs
   that also have aquic conditions in normal years (or artificial
   drainage) either:                                                JEJN. Other Hapludalfs that have all of the following:
        a. Within the upper 25 cm of the argillic horizon if          1. An abrupt textural change; and
        its upper boundary is within 50 cm of the mineral soil
        surface; or                                                   2. Redox depletions with chroma of 2 or less in layers
                                                                      that also have aquic conditions in normal years (or artificial
        b. Within 75 cm of the mineral soil surface if the upper      drainage) either:
        boundary of the argillic horizon is 50 cm or more below
        the mineral soil surface.                                           a. Within the upper 25 cm of the argillic horizon if
                                           Fragiaquic Hapludalfs            its upper boundary is within 50 cm of the mineral soil
                                                                            surface; or
JEJJ.    Other Hapludalfs that have both:                                   b. Within 75 cm of the mineral soil surface if the upper
   1.    Fragic soil properties:                                            boundary of the argillic horizon is 50 cm or more below
                                                                            the mineral soil surface; and
        a. In 30 percent or more of the volume of a layer 15 cm
        or more thick that has its upper boundary within 100 cm       3. A base saturation (by sum of cations) of less than 60
        of the mineral soil surface; or                               percent at a depth of 125 cm from the top of the argillic
                                                                      horizon, at a depth of 180 cm from the mineral soil surface,
        b. In 60 percent or more of the volume of a layer 15 cm
                                                                      or directly above a densic, lithic, or paralithic contact,
        or more thick; and
                                                                      whichever is shallowest.
   2. Saturation with water in one or more layers within 100                                                 Albaquultic Hapludalfs
   cm of the mineral soil surface in normal years for either or
   both:                                                            JEJO. Other Hapludalfs that have both:
54                                                                                                                    Keys to Soil Taxonomy



     1. An abrupt textural change; and                                   the upper 18 cm of the mineral soil (unmixed) or between the
                                                                         mineral soil surface and a depth of 18 cm after mixing; and
     2. Redox depletions with chroma of 2 or less in layers
     that also have aquic conditions in normal years (or artificial      2. Redox depletions with chroma of 2 or less in layers
     drainage) either:                                                   that also have aquic conditions in normal years (or artificial
                                                                         drainage) either:
        a. Within the upper 25 cm of the argillic horizon if
        its upper boundary is within 50 cm of the mineral soil                a. Within the upper 25 cm of the argillic horizon if
        surface; or                                                           its upper boundary is within 50 cm of the mineral soil
                                                                              surface; or
        b. Within 75 cm of the mineral soil surface if the upper
        boundary of the argillic horizon is 50 cm or more below               b. Within 75 cm of the mineral soil surface if the upper
        the mineral soil surface.                                             boundary of the argillic horizon is 50 cm or more below
                                             Albaquic Hapludalfs              the mineral soil surface.
                                                                                                                    Aquollic Hapludalfs
JEJP.    Other Hapludalfs that have both:
                                                                      JEJS. Other Hapludalfs that have redox depletions with
     1. Interfingering of albic materials in the upper part of the
                                                                      chroma of 2 or less in layers that also have aquic conditions in
     argillic horizon; and
                                                                      normal years (or artificial drainage) either:
     2. Redox depletions with chroma of 2 or less in layers
                                                                         1. Within the upper 25 cm of the argillic horizon if its
     that also have aquic conditions in normal years (or artificial
                                                                         upper boundary is within 50 cm of the mineral soil surface;
     drainage) either:
                                                                         or
        a. Within the upper 25 cm of the argillic horizon if
                                                                         2. Within 75 cm of the mineral soil surface if the upper
        its upper boundary is within 50 cm of the mineral soil
                                                                         boundary of the argillic horizon is 50 cm or more below the
        surface; or
                                                                         mineral soil surface.
        b. Within 75 cm of the mineral soil surface if the upper                                                    Aquic Hapludalfs
        boundary of the argillic horizon is 50 cm or more below
        the mineral soil surface.                                     JEJT.        Other Hapludalfs that have both:
                                           Glossaquic Hapludalfs
                                                                         1. A mollic epipedon, or the upper 18 cm of the mineral
                                                                         soil meets the color requirements for a mollic epipedon after
JEJQ.     Other Hapludalfs that have both:
                                                                         mixing; and
     1. Redox depletions with chroma of 2 or less in layers
                                                                         2. Saturation with water in 1 or more layers within 100 cm
     that also have aquic conditions in normal years (or artificial
                                                                         of the mineral soil surface in normal years for either or both:
     drainage) either:
                                                                              a.     20 or more consecutive days; or
        a. Within the upper 25 cm of the argillic horizon if
        its upper boundary is within 50 cm of the mineral soil                b.     30 or more cumulative days.
        surface; or                                                                                         Mollic Oxyaquic Hapludalfs
        b. Within 75 cm of the mineral soil surface if the upper
                                                                      JEJU. Other Hapludalfs that are saturated with water in one or
        boundary of the argillic horizon is 50 cm or more below
                                                                      more layers within 100 cm of the mineral soil surface in normal
        the mineral soil surface; and
                                                                      years for either or both:
     2. A base saturation (by sum of cations) of less than 60
                                                                         1.    20 or more consecutive days; or
     percent at a depth of 125 cm from the top of the argillic
     horizon, at a depth of 180 cm from the mineral soil surface,        2.    30 or more cumulative days.
     or directly above a densic, lithic, or paralithic contact,                                                       Oxyaquic Hapludalfs
     whichever is shallowest.
                                                Aquultic Hapludalfs   JEJV. Other Hapludalfs that have fragic soil properties:
                                                                         1. In 30 percent or more of the volume of a layer 15 cm or
JEJR.     Other Hapludalfs that have both:
                                                                         more thick that has its upper boundary within 100 cm of the
     1. A color value, moist, of 3 or less and a color value, dry,       mineral soil surface; or
     of 5 or less (crushed and smoothed sample) either throughout
Alfisols                                                                                                                               55



   2. In 60 percent or more of the volume of a layer 15 cm or          upper 18 cm of the mineral soil meets all the color requirements
   more thick.                                                         for a mollic epipedon after mixing.
                                           Fragic Hapludalfs                                                         Mollic Hapludalfs

JEJW. Other Hapludalfs that have an argillic horizon that              JEJZd.    Other Hapludalfs.
meets one of the following:                                                                                           Typic Hapludalfs
   1.    Consists entirely of lamellae; or
                                                                       Kandiudalfs
   2. Is a combination of two or more lamellae and one or
   more subhorizons with a thickness of 7.5 to 20 cm, each             Key to Subgroups
   layer with an overlying eluvial horizon; or                         JEEA. Kandiudalfs that have both:                                    A
                                                                                                                                            L
   3. Consists of one or more subhorizons that are more than              1. In one or more horizons within 75 cm of the mineral soil       F
   20 cm thick, each with an overlying eluvial horizon, and               surface, redox depletions with chroma of 2 or less and also
   above these horizons there are either:                                 aquic conditions for some time in normal years (or artificial
        a. Two or more lamellae with a combined thickness of              drainage); and
        5 cm or more (that may or may not be part of the argillic         2. 5 percent or more (by volume) plinthite in one or more
        horizon); or                                                      horizons within 150 cm of the mineral soil surface.
        b. A combination of lamellae (that may or may not be                                                Plinthaquic Kandiudalfs
        part of the argillic horizon) and one or more parts of the
        argillic horizon 7.5 to 20 cm thick, each with an overlying    JEEB. Other Kandiudalfs that have, in one or more horizons
        eluvial horizon.                                               within 75 cm of the mineral soil surface, redox depletions with
                                              Lamellic Hapludalfs      chroma of 2 or less and also aquic conditions for some time in
                                                                       normal years (or artificial drainage).
JEJX. Other Hapludalfs that have a sandy particle-size class                                                        Aquic Kandiudalfs
throughout the upper 75 cm of the argillic horizon or throughout
the entire argillic horizon if it is less than 75 cm thick.            JEEC. Other Kandiudalfs that are saturated with water in
                                            Psammentic Hapludalfs      one or more layers within 100 cm of the mineral soil surface in
                                                                       normal years for either or both:
JEJY. Other Hapludalfs that meet sandy or sandy-skeletal                  1.    20 or more consecutive days; or
particle-size class criteria throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth of      2.    30 or more cumulative days.
50 cm or more.                                                                                                    Oxyaquic Kandiudalfs
                                                Arenic Hapludalfs
                                                                       JEED.     Other Kandiudalfs that:
JEJZ. Other Hapludalfs that have interfingering of albic                  1. Meet sandy or sandy-skeletal particle-size class criteria
materials in one or more subhorizons of the argillic horizon.             throughout a layer extending from the mineral soil surface to
                                            Glossic Hapludalfs            the top of a kandic horizon at a depth of 50 to 100 cm; and

JEJZa.     Other Hapludalfs that:                                         2. Have 5 percent or more (by volume) plinthite in one or
                                                                          more horizons within 150 cm of the mineral soil surface.
   1.    Have an argillic horizon that is 35 cm or less thick; and                                     Arenic Plinthic Kandiudalfs
   2. Do not have a densic, lithic, or paralithic contact within
   100 cm of the mineral soil surface.                                 JEEE.     Other Kandiudalfs that:
                                            Inceptic Hapludalfs           1. Meet sandy or sandy-skeletal particle-size class criteria
                                                                          throughout a layer extending from the mineral soil surface to
JEJZb. Other Hapludalfs that have a base saturation (by sum               the top of a kandic horizon at a depth of 100 cm or more; and
of cations) of less than 60 percent at a depth of 125 cm below
the top of the argillic horizon, at a depth of 180 cm below               2. Have 5 percent or more (by volume) plinthite in one or
the mineral soil surface, or directly above a densic, lithic, or          more horizons within 150 cm of the mineral soil surface.
paralithic contact, whichever is shallowest.                                                      Grossarenic Plinthic Kandiudalfs
                                                  Ultic Hapludalfs
                                                                       JEEF. Other Kandiudalfs that meet sandy or sandy-skeletal
JEJZc.     Other Hapludalfs that have a mollic epipedon, or the        particle-size class criteria throughout a layer extending from the
56                                                                                                              Keys to Soil Taxonomy



mineral soil surface to the top of a kandic horizon at a depth of    JEFD. Other Kanhapludalfs that have, in all subhorizons in
50 to 100 cm.                                                        the upper 100 cm of the kandic horizon or throughout the entire
                                             Arenic Kandiudalfs      kandic horizon if less than 100 cm thick, more than 50 percent
                                                                     colors that have all of the following:
JEEG. Other Kandiudalfs that meet sandy or sandy-skeletal
                                                                        1.    Hue of 2.5YR or redder; and
particle-size class criteria throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of       2. Value, moist, of 3 or less; and
100 cm or more.
                                        Grossarenic Kandiudalfs         3. Dry value no more than 1 unit higher than the moist
                                                                        value.
JEEH. Other Kandiudalfs that have 5 percent or more (by                                                    Rhodic Kanhapludalfs
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.                                                JEFE. Other Kanhapludalfs.
                                          Plinthic Kandiudalfs                                                   Typic Kanhapludalfs

JEEI. Other Kandiudalfs that have, in all subhorizons in the         Natrudalfs
upper 100 cm of the kandic horizon or throughout the entire          Key to Subgroups
kandic horizon if less than 100 cm thick, more than 50 percent
colors that have all of the following:                               JEAA. Natrudalfs that have one or both of the following:
     1.   Hue of 2.5YR or redder; and                                   1. Cracks within 125 cm of the mineral soil surface that are
                                                                        5 mm or more wide through a thickness of 30 cm or more
     2. Value, moist, of 3 or less; and
                                                                        for some time in normal years and slickensides or wedge-
     3. Dry value no more than 1 unit higher than the moist             shaped peds in a layer 15 cm or more thick that has its upper
     value.                                                             boundary within 125 cm of the mineral soil surface; or
                                          Rhodic Kandiudalfs
                                                                        2. A linear extensibility of 6.0 cm or more between the
                                                                        mineral soil surface and either a depth of 100 cm or a densic,
JEEJ. Other Kandiudalfs that have a mollic epipedon, or the
                                                                        lithic, or paralithic contact, whichever is shallower.
upper 18 cm of the mineral soil meets the color requirements for
                                                                                                                      Vertic Natrudalfs
a mollic epipedon after mixing.
                                           Mollic Kandiudalfs
                                                                     JEAB. Other Natrudalfs that have both:
JEEK.      Other Kandiudalfs.                                           1. Either a glossic horizon or interfingering of albic
                                               Typic Kandiudalfs        materials into the natric horizon; and
                                                                        2. Redox depletions with chroma of 2 or less in layers
Kanhapludalfs
                                                                        that also have aquic conditions in normal years (or artificial
Key to Subgroups                                                        drainage) either:
JEFA. Kanhapludalfs that have a lithic contact within 50 cm                  a. Within the upper 25 cm of the natric horizon if
of the mineral soil surface.                                                 its upper boundary is within 50 cm of the mineral soil
                                        Lithic Kanhapludalfs                 surface; or

JEFB. Other Kanhapludalfs that have, in one or more horizons                 b. Within 75 cm of the mineral soil surface if the upper
within 75 cm of the mineral soil surface, redox depletions with              boundary of the natric horizon is 50 cm or more below the
chroma of 2 or less and also aquic conditions for some time in               mineral soil surface.
normal years (or artificial drainage).                                                                          Glossaquic Natrudalfs
                                           Aquic Kanhapludalfs
                                                                     JEAC. Other Natrudalfs that have redox depletions with
JEFC. Other Kanhapludalfs that are saturated with water in           chroma of 2 or less in layers that also have aquic conditions in
one or more layers within 100 cm of the mineral soil surface in      normal years (or artificial drainage) either:
normal years for either or both:                                        1. Within the upper 25 cm of the natric horizon if its upper
     1.   20 or more consecutive days; or                               boundary is within 50 cm of the mineral soil surface; or

     2.   30 or more cumulative days.                                   2. Within 75 cm of the mineral soil surface if the upper
                                          Oxyaquic Kanhapludalfs
Alfisols                                                                                                                               57



   boundary of the natric horizon is 50 cm or more below the             1.    Fragic soil properties:
   mineral soil surface.
                                                                              a. In 30 percent or more of the volume of a layer 15 cm
                                              Aquic Natrudalfs
                                                                              or more thick that has its upper boundary within 100 cm
                                                                              of the mineral soil surface; or
JEAD.      Other Natrudalfs.
                                                Typic Natrudalfs              b. In 60 percent or more of the volume of a layer 15 cm
                                                                              or more thick; and
Paleudalfs                                                               2. Redox depletions with chroma of 2 or less in layers
Key to Subgroups                                                         that also have aquic conditions in normal years (or artificial
                                                                         drainage) either:
JEGA.      Paleudalfs that have one or both of the following:                                                                               A
                                                                              a. Within the upper 25 cm of the argillic horizon if          L
                                                                                                                                            F
   1. Cracks within 125 cm of the mineral soil surface that are               its upper boundary is within 50 cm of the mineral soil
   5 mm or more wide through a thickness of 30 cm or more                     surface; or
   for some time in normal years and slickensides or wedge-
                                                                              b. Within 75 cm of the mineral soil surface if the upper
   shaped peds in a layer 15 cm or more thick that has its upper
   boundary within 125 cm of the mineral soil surface; or                     boundary of the argillic horizon is 50 cm or more below
                                                                              the mineral soil surface.
   2. A linear extensibility of 6.0 cm or more between the                                                        Fragiaquic Paleudalfs
   mineral soil surface and either a depth of 100 cm or a densic,
   lithic, or paralithic contact, whichever is shallower.             JEGF. Other Paleudalfs that have both:
                                                 Vertic Paleudalfs
                                                                         1. In one or more horizons within 75 cm of the mineral soil
                                                                         surface, redox depletions with chroma of 2 or less and also
JEGB. Other Paleudalfs that have, throughout one or more                 aquic conditions for some time in normal years (or artificial
horizons with a total thickness of 18 cm or more within 75 cm            drainage); and
of the mineral soil surface, a fine-earth fraction with both a bulk      2. 5 percent or more (by volume) plinthite in one or more
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,        horizons within 150 cm of the mineral soil surface.
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling                                                Plinthaquic Paleudalfs
more than 1.0.
                                                 Andic Paleudalfs     JEGG. Other Paleudalfs that have both:

JEGC. Other Paleudalfs that have, throughout one or more                 1. In one or more horizons within 75 cm of the mineral soil
horizons with a total thickness of 18 cm or more within 75 cm            surface, redox depletions with chroma of 2 or less and also
of the mineral soil surface, one or both of the following:               aquic conditions for some time in normal years (or artificial
                                                                         drainage); and
   1. More than 35 percent (by volume) fragments coarser
   than 2.0 mm, of which more than 66 percent is cinders,                2. A glossic horizon or, in the upper part of the argillic
   pumice, and pumicelike fragments; or                                  horizon, one or more subhorizons that have 5 percent or
                                                                         more (by volume) clay depletions with chroma of 2 or less.
   2. A fine-earth fraction containing 30 percent or more                                                      Glossaquic Paleudalfs
   particles 0.02 to 2.0 mm in diameter; and
                                                                      JEGH.      Other Paleudalfs that have both:
      a. In the 0.02 to 2.0 mm fraction, 5 percent or more
      volcanic glass; and                                                1. In one or more horizons within 75 cm of the mineral soil
                                                                         surface, redox depletions with chroma of 2 or less and also
      b. [(Al plus 1/2 Fe, percent extracted by ammonium
                                                                         aquic conditions for some time in normal years (or artificial
      oxalate) times 60] plus the volcanic glass (percent) is
                                                                         drainage); and
      equal to 30 or more.
                                           Vitrandic Paleudalfs          2. A clay increase of 15 percent or more (absolute) in the
                                                                         fine-earth fraction within a vertical distance of 2.5 cm at the
JEGD.      Other Paleudalfs that have anthraquic conditions.             upper boundary of the argillic horizon.
                                          Anthraquic Paleudalfs                                                     Albaquic Paleudalfs

                                                                      JEGI. Other Paleudalfs that have, in one or more horizons
JEGE.      Other Paleudalfs that have both:                           within 75 cm of the mineral soil surface, redox depletions with
58                                                                                                               Keys to Soil Taxonomy



chroma of 2 or less and also aquic conditions for some time in                b. A combination of lamellae (that may or may not be
normal years (or artificial drainage).                                        part of the argillic horizon) and one or more parts of the
                                               Aquic Paleudalfs               argillic horizon 7.5 to 20 cm thick, each with an overlying
                                                                              eluvial horizon.
JEGJ. Other Paleudalfs that are saturated with water in one or                                                       Lamellic Paleudalfs
more layers within 100 cm of the mineral soil surface in normal
years for either or both:                                             JEGO. Other Paleudalfs that have a sandy particle-size class
                                                                      throughout the upper 75 cm of the argillic horizon or throughout
     1.    20 or more consecutive days; or
                                                                      the entire argillic horizon if it is less than 75 cm thick.
     2.    30 or more cumulative days.                                                                             Psammentic Paleudalfs
                                               Oxyaquic Paleudalfs
                                                                      JEGP. Other Paleudalfs that meet sandy or sandy-skeletal
JEGK.        Other Paleudalfs that have fragic soil properties:       particle-size class criteria throughout a layer extending from the
                                                                      mineral soil surface to the top of an argillic horizon at a depth of
     1. In 30 percent or more of the volume of a layer 15 cm or
                                                                      50 to 100 cm.
     more thick that has its upper boundary within 100 cm of the
                                                                                                                       Arenic Paleudalfs
     mineral soil surface; or
     2. In 60 percent or more of the volume of a layer 15 cm or       JEGQ. Other Paleudalfs that meet sandy or sandy-skeletal
     more thick.                                                      particle-size class criteria throughout a layer extending from the
                                              Fragic Paleudalfs       mineral soil surface to the top of an argillic horizon at a depth of
                                                                      100 cm or more.
JEGL. Other Paleudalfs that:                                                                                     Grossarenic Paleudalfs

     1. Meet sandy or sandy-skeletal particle-size class criteria     JEGR. Other Paleudalfs that have 5 percent or more (by
     throughout a layer extending from the mineral soil surface to    volume) plinthite in one or more horizons within 150 cm of the
     the top of an argillic horizon at a depth of 50 to 100 cm; and   mineral soil surface.
                                                                                                                 Plinthic Paleudalfs
     2. Have 5 percent or more (by volume) plinthite in one or
     more horizons within 150 cm of the mineral soil surface.
                                                                      JEGS.     Other Paleudalfs that have either:
                                     Arenic Plinthic Paleudalfs
                                                                         1. A glossic horizon; or
JEGM. Other Paleudalfs that:
                                                                         2. In the upper part of the argillic horizon, one or more
     1. Meet sandy or sandy-skeletal particle-size class criteria        subhorizons that have 5 percent or more (by volume)
     throughout a layer extending from the mineral soil surface to       skeletans with chroma of 2 or less; or
     the top of an argillic horizon at a depth of 100 cm or more;
     and                                                                 3. 5 percent or more (by volume) albic materials in some
                                                                         subhorizon of the argillic horizon.
     2. Have 5 percent or more (by volume) plinthite in one or                                                   Glossic Paleudalfs
     more horizons within 150 cm of the mineral soil surface.
                               Grossarenic Plinthic Paleudalfs        JEGT. Other Paleudalfs that have, in all subhorizons in the
                                                                      upper 100 cm of the argillic horizon or throughout the entire
JEGN. Other Paleudalfs that have an argillic horizon that             argillic horizon if less than 100 cm thick, more than 50 percent
meets one of the following:                                           colors that have all of the following:
     1.    Consists entirely of lamellae; or                             1.    Hue of 2.5YR or redder; and
     2. Is a combination of two or more lamellae and one or              2. Value, moist, of 3 or less; and
     more subhorizons with a thickness of 7.5 to 20 cm, each
     layer with an overlying eluvial horizon; or                         3. Dry value no more than 1 unit higher than the moist
                                                                         value.
     3. Consists of one or more subhorizons that are more than
                                                                                                                 Rhodic Paleudalfs
     20 cm thick, each with an overlying eluvial horizon, and
     above these horizons there are either:
                                                                      JEGU. Other Paleudalfs that have a mollic epipedon, or the
          a. Two or more lamellae with a combined thickness of        upper 18 cm of the mineral soil meets the color requirements for
          5 cm or more (that may or may not be part of the argillic   a mollic epipedon after mixing.
          horizon); or                                                                                              Mollic Paleudalfs
Alfisols                                                                                                                                  59



JEGV.      Other Paleudalfs.                                                   a. Within 150 cm of the mineral soil surface, either:
                                                 Typic Paleudalfs
                                                                                  (1) With increasing depth, no clay decrease of 20
                                                                                  percent or more (relative) from the maximum clay
Rhodudalfs                                                                        content [Clay is measured noncarbonate clay or is
Key to Subgroups                                                                  based on the following formula: Clay % = 2.5(% water
                                                                                  retained at 1500 kPa tension - % organic carbon),
JEHA. All Rhodudalfs (provisionally).                                             whichever value is greater, but no more than 100]; or
                                                Typic Rhodudalfs
                                                                                  (2) 5 percent or more (by volume) skeletans on
                                                                                  faces of peds in the layer that has a 20 percent lower
Ustalfs                                                                           clay content and, below that layer, a clay increase of 3     A
Key to Great Groups                                                               percent or more (absolute) in the fine-earth fraction;       L
                                                                                                                                               F
                                                                                  and
JCA. Ustalfs that have a duripan within 100 cm of the mineral
soil surface.                                                                  b. In the lower one-half of the argillic horizon, one or
                                             Durustalfs, p. 59                 more subhorizons with either or both:
                                                                                  (1) Hue of 7.5YR or redder and chroma of 5 or more
JCB. Other Ustalfs that have one or more horizons within 150                      in 50 percent or more of the matrix; or
cm of the mineral soil surface in which plinthite either forms a
continuous phase or constitutes one-half or more of the volume.                   (2) Common or many coarse redox concentrations
                                             Plinthustalfs, p. 70                 with hue of 7.5YR or redder or chroma of 6 or more,
                                                                                  or both; or
JCC. Other Ustalfs that have a natric horizon.                            3. No densic, lithic, or paralithic contact within 50 cm of
                                             Natrustalfs, p. 65           the mineral soil surface and an argillic horizon that has both:

JCD.     Other Ustalfs that meet all of the following:                         a. 35 percent or more noncarbonate clay throughout one
                                                                               or more subhorizons in its upper part; and
   1.    Have a kandic horizon; and
                                                                               b. At its upper boundary, a clay increase (in the fine-
   2. Do not have a densic, lithic, paralithic, or petroferric                 earth fraction) of either 20 percent or more (absolute)
   contact within 150 cm of the mineral soil surface; and                      within a vertical distance of 7.5 cm or of 15 percent or
   3. Within 150 cm of the mineral soil surface, either:                       more (absolute) within a vertical distance of 2.5 cm.
                                                                                                                         Paleustalfs, p. 67
        a. Do not have a clay decrease with increasing depth
        of 20 percent or more (relative) from the maximum clay
        content [Clay is measured noncarbonate clay or is based        JCG. Other Ustalfs that have, in all subhorizons in the upper
        on the following formula: Clay % = 2.5(% water retained        100 cm of the argillic horizon or throughout the entire argillic
        at 1500 kPa tension - % organic carbon), whichever value       horizon if less than 100 cm thick, more than 50 percent colors
        is greater, but no more than 100]; or                          that have all of the following:

        b. Have 5 percent or more (by volume) skeletans on                1.    Hue of 2.5YR or redder; and
        faces of peds in the layer that has a 20 percent lower clay       2. Value, moist, of 3 or less; and
        content and, below that layer, a clay increase of 3 percent
        or more (absolute) in the fine-earth fraction.                    3. Dry value no more than 1 unit higher than the moist
                                                 Kandiustalfs, p. 63      value.
                                                                                                                  Rhodustalfs, p. 70
JCE. Other Ustalfs that have a kandic horizon.
                                        Kanhaplustalfs, p. 64          JCH. Other Ustalfs.
                                                                                                                        Haplustalfs, p. 60
JCF. Other Ustalfs that have one or more of the following:
                                                                       Durustalfs
   1. A petrocalcic horizon within 150 cm of the mineral soil
   surface; or                                                         Key to Subgroups
   2. No densic, lithic, or paralithic contact within 150 cm of        JCAA. All Durustalfs (provisionally).
   the mineral soil surface and an argillic horizon that has both:                                                       Typic Durustalfs
60                                                                                                              Keys to Soil Taxonomy



Haplustalfs                                                                 control section that in normal years is dry in all parts for
                                                                            four-tenths or more of the cumulative days per year when
Key to Subgroups                                                            the soil temperature at a depth of 50 cm below the soil
JCHA. Haplustalfs that have a lithic contact within 50 cm of                surface is higher than 5 oC; or
the mineral soil surface.                                                   b. A mesic or thermic soil temperature regime and a
                                           Lithic Haplustalfs               moisture control section that in normal years is dry in
                                                                            some part for six-tenths or more of the cumulative days
JCHB. Other Haplustalfs that have both:                                     per year when the soil temperature at a depth of 50 cm
     1.    One or both of the following:                                    below the soil surface is higher than 5 oC; or
          a. Cracks within 125 cm of the mineral soil surface that          c. A hyperthermic, isomesic, or warmer iso soil
          are 5 mm or more wide through a thickness of 30 cm or             temperature regime and a moisture control section that in
          more for some time in normal years and slickensides or            normal years:
          wedge-shaped peds in a layer 15 cm or more thick that                (1) Is moist in some or all parts for less than 90
          has its upper boundary within 125 cm of the mineral soil             consecutive days per year when the soil temperature at
          surface; or                                                          a depth of 50 cm below the soil surface is higher than
          b. A linear extensibility of 6.0 cm or more between                  8 oC; and
          the mineral soil surface and either a depth of 100 cm                (2) Is dry in some part for six-tenths or more of the
          or a densic, lithic, or paralithic contact, whichever is             cumulative days per year when the soil temperature at
          shallower; and                                                       a depth of 50 cm below the soil surface is higher than
     2. In one or more horizons within 75 cm of the mineral soil               5 oC; and
     surface, redox depletions with chroma of 2 or less and also       2. One or both of the following:
     aquic conditions for some time in normal years (or artificial
     drainage).                                                             a. Cracks within 125 cm of the soil surface that are 5
                                           Aquertic Haplustalfs             mm or more wide through a thickness of 30 cm or more
                                                                            for some time in normal years and slickensides or wedge-
JCHC. Other Haplustalfs that have both:                                     shaped peds in a layer 15 cm or more thick that has its
                                                                            upper boundary within 125 cm of the soil surface; or
     1.    One or both of the following:
                                                                            b. A linear extensibility of 6.0 cm or more between the
          a. Cracks within 125 cm of the mineral soil surface that          soil surface and either a depth of 100 cm or a densic,
          are 5 mm or more wide through a thickness of 30 cm or             lithic, or paralithic contact, whichever is shallower.
          more for some time in normal years and slickensides or                                                  Torrertic Haplustalfs
          wedge-shaped peds in a layer 15 cm or more thick that
          has its upper boundary within 125 cm of the mineral soil   JCHE. Other Haplustalfs that have both:
          surface; or
                                                                       1. When neither irrigated nor fallowed to store moisture,
          b. A linear extensibility of 6.0 cm or more between          either:
          the mineral soil surface and either a depth of 100 cm
          or a densic, lithic, or paralithic contact, whichever is          a. A mesic or thermic soil temperature regime and a
          shallower; and                                                    moisture control section that in normal years is dry in
                                                                            some part for four-tenths or less of the cumulative days
     2. Saturation with water in one or more layers within 100              per year when the soil temperature at a depth of 50 cm
     cm of the mineral soil surface in normal years for either or           below the soil surface is higher than 5 oC; or
     both:
                                                                            b. A hyperthermic, isomesic, or warmer iso soil
          a.   20 or more consecutive days; or                              temperature regime and a moisture control section that in
          b.   30 or more cumulative days.                                  normal years is dry in some or all parts for less than 120
                                      Oxyaquic Vertic Haplustalfs           cumulative days per year when the soil temperature at a
                                                                            depth of 50 cm below the soil surface is higher than 8 oC;
JCHD. Other Haplustalfs that have both of the following:                    and
     1. When neither irrigated nor fallowed to store moisture,         2.    One or both of the following:
     one of the following:                                                  a. Cracks within 125 cm of the mineral soil surface that
          a. A frigid soil temperature regime and a moisture                are 5 mm or more wide through a thickness of 30 cm or
Alfisols                                                                                                                               61



      more for some time in normal years and slickensides or              2.    30 or more cumulative days.
      wedge-shaped peds in a layer 15 cm or more thick that                                                         Oxyaquic Haplustalfs
      has its upper boundary within 125 cm of the mineral soil
      surface; or                                                      JCHK. Other Haplustalfs that have, throughout one or more
                                                                       horizons with a total thickness of 18 cm or more within 75 cm
      b. A linear extensibility of 6.0 cm or more between the
                                                                       of the mineral soil surface, one or both of the following:
      mineral soil surface and either a depth of 100 cm or a
      densic, lithic, or paralithic contact, whichever is shallower.      1. More than 35 percent (by volume) fragments coarser
                                              Udertic Haplustalfs         than 2.0 mm, of which more than 66 percent is cinders,
                                                                          pumice, and pumicelike fragments; or
JCHF. Other Haplustalfs that have one or both of the
                                                                          2. A fine-earth fraction containing 30 percent or more             A
following:
                                                                          particles 0.02 to 2.0 mm in diameter; and                          L
                                                                                                                                             F
   1. Cracks within 125 cm of the mineral soil surface that are
                                                                               a. In the 0.02 to 2.0 mm fraction, 5 percent or more
   5 mm or more wide through a thickness of 30 cm or more
                                                                               volcanic glass; and
   for some time in normal years and slickensides or wedge-
   shaped peds in a layer 15 cm or more thick that has its upper               b. [(Al plus 1/2 Fe, percent extracted by ammonium
   boundary within 125 cm of the mineral soil surface; or                      oxalate) times 60] plus the volcanic glass (percent) is
                                                                               equal to 30 or more.
   2. A linear extensibility of 6.0 cm or more between the
                                                                                                                   Vitrandic Haplustalfs
   mineral soil surface and either a depth of 100 cm or a densic,
   lithic, or paralithic contact, whichever is shallower.
                                                                       JCHL. Other Haplustalfs that have an argillic horizon that
                                                Vertic Haplustalfs
                                                                       meets one of the following:
JCHG.      Other Haplustalfs that:                                        1.    Consists entirely of lamellae; or
   1. In one or more horizons within 75 cm of the mineral                 2. Is a combination of two or more lamellae and one or
   soil surface, have redox depletions with chroma of 2 or less           more subhorizons with a thickness of 7.5 to 20 cm, each
   and also aquic conditions for some time in normal years (or            layer with an overlying eluvial horizon; or
   artificial drainage); and
                                                                          3. Consists of one or more subhorizons that are more than
   2. Meet sandy or sandy-skeletal particle-size class criteria           20 cm thick, each with an overlying eluvial horizon, and
   throughout a layer extending from the mineral soil surface to          above these horizons there are either:
   the top of an argillic horizon at a depth of 50 to 100 cm.
                                        Aquic Arenic Haplustalfs               a. Two or more lamellae with a combined thickness of
                                                                               5 cm or more (that may or may not be part of the argillic
JCHH. Other Haplustalfs that have both:                                        horizon); or

   1. In one or more horizons within 75 cm of the mineral soil                 b. A combination of lamellae (that may or may not be
   surface, redox depletions with chroma of 2 or less and also                 part of the argillic horizon) and one or more parts of the
   aquic conditions for some time in normal years (or artificial               argillic horizon 7.5 to 20 cm thick, each with an overlying
   drainage); and                                                              eluvial horizon.
                                                                                                                     Lamellic Haplustalfs
   2. An argillic horizon that has a base saturation (by sum of
   cations) of less than 75 percent throughout.                        JCHM. Other Haplustalfs that have a sandy particle-size class
                                           Aquultic Haplustalfs        throughout the upper 75 cm of the argillic horizon or throughout
                                                                       the entire argillic horizon if it is less than 75 cm thick.
JCHI. Other Haplustalfs that have, in one or more horizons                                                         Psammentic Haplustalfs
within 75 cm of the mineral soil surface, redox depletions with
chroma of 2 or less and also aquic conditions for some time in         JCHN. Other Haplustalfs that:
normal years (or artificial drainage).
                                              Aquic Haplustalfs           1. Meet sandy or sandy-skeletal particle-size class criteria
                                                                          throughout a layer extending from the mineral soil surface
JCHJ. Other Haplustalfs that are saturated with water in one or           to the top of an argillic horizon at a depth of 50 cm or more;
more layers within 100 cm of the mineral soil surface in normal           and
years for either or both:
                                                                          2. When neither irrigated nor fallowed to store moisture,
   1. 20 or more consecutive days; or                                     have one of the following:
62                                                                                                                Keys to Soil Taxonomy



       a. A frigid soil temperature regime and a moisture                         depth of 50 cm below the soil surface is higher than
       control section that in normal years is dry in all parts for               8 oC; and
       four-tenths or more of the cumulative days per year when
                                                                                  (2) Is dry in some part for six-tenths or more of the
       the soil temperature at a depth of 50 cm below the soil
                                                                                  cumulative days per year when the soil temperature at
       surface is higher than 5 oC; or
                                                                                  a depth of 50 cm below the soil surface is higher than
       b. A mesic or thermic soil temperature regime and a                        5 oC.
       moisture control section that in normal years is dry in                                                      Calcidic Haplustalfs
       some part for six-tenths or more of the cumulative days
       per year when the soil temperature at a depth of 50 cm          JCHQ. Other Haplustalfs that, when neither irrigated nor
       below the soil surface is higher than 5 oC; or                  fallowed to store moisture, have one of the following:
       c. A hyperthermic, isomesic, or warmer iso soil                    1. A frigid soil temperature regime and a moisture control
       temperature regime and a moisture control section that in          section that in normal years is dry in all parts for four-
       normal years:                                                      tenths or more of the cumulative days per year when the soil
                                                                          temperature at a depth of 50 cm below the soil surface is
          (1) Is moist in some or all parts for less than 90
                                                                          higher than 5 oC; or
          consecutive days per year when the soil temperature at
          a depth of 50 cm below the soil surface is higher than          2. A mesic or thermic soil temperature regime and a
          8 oC; and                                                       moisture control section that in normal years is dry in some
                                                                          part for six-tenths or more of the cumulative days per year
          (2) Is dry in some part for six-tenths or more of the
                                                                          when the soil temperature at a depth of 50 cm below the soil
          cumulative days per year when the soil temperature at a
                                                                          surface is higher than 5 oC; or
          depth of 50 cm below the soil surface is higher than
          5 oC.                                                           3. A hyperthermic, isomesic, or warmer iso soil
                                      Arenic Aridic Haplustalfs           temperature regime and a moisture control section that in
                                                                          normal years:
JCHO. Other Haplustalfs that meet sandy or sandy-skeletal
                                                                               a. Is moist in some or all parts for less than 90
particle-size class criteria throughout a layer extending from the
                                                                               consecutive days per year when the soil temperature at a
mineral soil surface to the top of an argillic horizon at a depth of
                                                                               depth of 50 cm below the soil surface is higher than 8 oC;
50 cm or more.
                                                                               and
                                                Arenic Haplustalfs
                                                                               b. Is dry in some part for six-tenths or more of the
JCHP. Other Haplustalfs that have both:                                        cumulative days per year when the soil temperature at a
                                                                               depth of 50 cm below the soil surface is higher than 5 oC.
     1. A calcic horizon within 100 cm of the mineral soil
                                                                                                                      Aridic Haplustalfs
     surface; and
     2. When neither irrigated nor fallowed to store moisture,         JCHR. Other Haplustalfs that have a CEC of less than 24
     one of the following:                                             cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more
                                                                       either of the argillic horizon if less than 100 cm thick or of its
       a. A frigid soil temperature regime and a moisture
                                                                       upper 100 cm.
       control section that in normal years is dry in all parts for
                                                                                                                   Kanhaplic Haplustalfs
       four-tenths or more of the cumulative days per year when
       the soil temperature at a depth of 50 cm below the soil
                                                                       JCHS.     Other Haplustalfs that:
       surface is higher than 5 oC; or
                                                                          1.    Have an argillic horizon that is 35 cm or less thick; and
       b. A mesic or thermic soil temperature regime and a
       moisture control section that in normal years is dry in            2. Do not have a densic, lithic, or paralithic contact within
       some part for six-tenths or more of the cumulative days            100 cm of the mineral soil surface.
       per year when the soil temperature at a depth of 50 cm                                                     Inceptic Haplustalfs
       below the soil surface is higher than 5 oC; or
                                                                       JCHT. Other Haplustalfs that have both:
       c. A hyperthermic, isomesic, or warmer iso soil
       temperature regime and a moisture control section that in          1. A calcic horizon within 100 cm of the mineral soil
       normal years:                                                      surface; and
          (1) Is moist in some or all parts for less than 90              2. When neither irrigated nor fallowed to store moisture,
          consecutive days per year when the temperature at a             one of the following:
Alfisols                                                                                                                            63



      a. A frigid soil temperature regime and a moisture            Kandiustalfs
      control section that in normal years is dry in some or all
      parts for less than 105 cumulative days per year when the     Key to Subgroups
      soil temperature at a depth of 50 cm below the soil surface   JCDA. Kandiustalfs that meet sandy or sandy-skeletal
      is higher than 5 oC; or                                       particle-size class criteria throughout a layer extending from the
                                                                    mineral soil surface to the top of a kandic horizon at a depth of
      b. A mesic or thermic soil temperature regime and a
                                                                    100 cm or more.
      moisture control section that in normal years is dry in
                                                                                                            Grossarenic Kandiustalfs
      some part for four-tenths or less of the cumulative days
      per year when the soil temperature at a depth of 50 cm
                                                                    JCDB. Other Kandiustalfs that:
      below the soil surface is higher than 5 oC; or
                                                                       1. In one or more horizons within 75 cm of the mineral            A
      c. A hyperthermic, isomesic, or warmer iso soil                                                                                    L
                                                                       soil surface, have redox depletions with chroma of 2 or less      F
      temperature regime and a moisture control section that           and also aquic conditions for some time in normal years (or
      in normal years is dry in some or all parts for less than        artificial drainage); and
      120 cumulative days per year when the soil temperature
      at a depth of 50 cm below the soil surface is higher than        2. Meet sandy or sandy-skeletal particle-size class criteria
      8 oC.                                                            throughout a layer extending from the mineral soil surface to
                                       Calcic Udic Haplustalfs         the top of a kandic horizon at a depth of 50 to 100 cm.
                                                                                                         Aquic Arenic Kandiustalfs
JCHU. Other Haplustalfs that have an argillic horizon with
a base saturation (by sum of cations) of less than 75 percent       JCDC. Other Kandiustalfs that have 5 percent or more (by
throughout.                                                         volume) plinthite in one or more horizons within 150 cm of the
                                                Ultic Haplustalfs   mineral soil surface.
                                                                                                             Plinthic Kandiustalfs
JCHV. Other Haplustalfs that have a calcic horizon within 100
                                                                    JCDD. Other Kandiustalfs that have, in one or more horizons
cm of the mineral soil surface.
                                                                    within 75 cm of the mineral soil surface, redox depletions with
                                           Calcic Haplustalfs
                                                                    chroma of 2 or less and also aquic conditions for some time in
                                                                    normal years (or artificial drainage).
JCHW. Other Haplustalfs that, when neither irrigated nor                                                         Aquic Kandiustalfs
fallowed to store moisture, have one of the following:
   1. A frigid soil temperature regime and a moisture control       JCDE.    Other Kandiustalfs that:
   section that in normal years is dry in some or all parts            1. Meet sandy or sandy-skeletal particle-size class criteria
   for less than 105 cumulative days per year when the soil            throughout a layer extending from the mineral soil surface to
   temperature at a depth of 50 cm below the soil surface is           the top of a kandic horizon at a depth of 50 to 100 cm; and
   higher than 5 oC; or
                                                                       2. When neither irrigated nor fallowed to store moisture,
   2. A mesic or thermic soil temperature regime and a                 have either:
   moisture control section that in normal years is dry in some
   part for four-tenths or less of the cumulative days per year           a. A mesic or thermic soil temperature regime and a
   when the soil temperature at a depth of 50 cm below the soil           moisture control section that in normal years is dry in
   surface is higher than 5 oC; or                                        some part for six-tenths or more of the cumulative days
                                                                          per year when the soil temperature at a depth of 50 cm
   3. A hyperthermic, isomesic, or warmer iso soil                        below the soil surface is higher than 5 oC; or
   temperature regime and a moisture control section that in
   normal years is dry in some or all parts for less than 120             b. A hyperthermic, isomesic, or warmer iso soil
   cumulative days per year when the soil temperature at a                temperature regime and a moisture control section that in
   depth of 50 cm below the soil surface is higher than 8 oC.             normal years:
                                                 Udic Haplustalfs            (1) Is moist in some or all parts for less than 90
                                                                             consecutive days per year when the soil temperature at
JCHX.      Other Haplustalfs.                                                a depth of 50 cm below the soil surface is higher than
                                              Typic Haplustalfs              8 oC; and
64                                                                                                                Keys to Soil Taxonomy



             (2) Is dry in some part for six-tenths or more of the       2. Value, moist, of 3 or less; and
             cumulative days per year when the soil temperature at
                                                                         3. Dry value no more than 1 unit higher than the moist
             a depth of 50 cm below the soil surface is higher than
                                                                         value.
             5 oC.
                                                                                                              Rhodic Kandiustalfs
                                       Arenic Aridic Kandiustalfs
                                                                       JCDJ.     Other Kandiustalfs.
JCDF. Other Kandiustalfs that meet sandy or sandy-skeletal
                                                                                                                     Typic Kandiustalfs
particle-size class criteria throughout a layer extending from the
mineral soil surface to the top of a kandic horizon at a depth of
50 to 100 cm.                                                          Kanhaplustalfs
                                              Arenic Kandiustalfs      Key to Subgroups

JCDG. Other Kandiustalfs that, when neither irrigated nor              JCEA. Kanhaplustalfs that have a lithic contact within 50 cm
fallowed to store moisture, have either:                               of the mineral soil surface.
                                                                                                              Lithic Kanhaplustalfs
     1. A mesic or thermic soil temperature regime and a
     moisture control section that in normal years is dry in some      JCEB. Other Kanhaplustalfs that have, in one or more
     part for six-tenths or more of the cumulative days per year       horizons within 75 cm of the mineral soil surface, redox
     when the soil temperature at a depth of 50 cm below the soil      depletions with chroma of 2 or less and also aquic conditions
     surface is higher than 5 oC; or                                   for some time in normal years (or artificial drainage).
                                                                                                                 Aquic Kanhaplustalfs
     2. A hyperthermic, isomesic, or warmer iso soil
     temperature regime and a moisture control section that in
                                                                       JCEC. Other Kanhaplustalfs that, when neither irrigated nor
     normal years:
                                                                       fallowed to store moisture, have either:
          a. Is moist in some or all parts for less than 90
                                                                         1. A mesic or thermic soil temperature regime and a
          consecutive days per year when the soil temperature at a
                                                                         moisture control section that in normal years is dry in some
          depth of 50 cm below the soil surface is higher than 8 oC;
                                                                         part for six-tenths or more of the cumulative days per year
          and
                                                                         when the soil temperature at a depth of 50 cm below the soil
          b. Is dry in some part for six-tenths or more of the           surface is higher than 5 oC; or
          cumulative days per year when the soil temperature at a
                                                                         2. A hyperthermic, isomesic, or warmer iso soil
          depth of 50 cm below the soil surface is higher than 5 oC.
                                                                         temperature regime and a moisture control section that in
                                                Aridic Kandiustalfs
                                                                         normal years:
JCDH. Other Kandiustalfs that, when neither irrigated nor                      a. Is moist in some or all parts for less than 90
fallowed to store moisture, have either:                                       consecutive days per year when the soil temperature at a
                                                                               depth of 50 cm below the soil surface is higher than 8 oC;
     1. A mesic or thermic soil temperature regime and a
                                                                               and
     moisture control section that in normal years is dry in some
     part for 135 cumulative days or less per year when the soil               b. Is dry in some part for six-tenths or more of the
     temperature at a depth of 50 cm below the soil surface is                 cumulative days per year when the soil temperature at a
     higher than 5 oC; or                                                      depth of 50 cm below the soil surface is higher than 5 oC.
                                                                                                                  Aridic Kanhaplustalfs
     2. A hyperthermic, isomesic, or warmer iso soil
     temperature regime and a moisture control section that in
                                                                       JCED. Other Kanhaplustalfs that, when neither irrigated nor
     normal years is dry in some or all parts for less than 120
                                                                       fallowed to store moisture, have either:
     cumulative days per year when the soil temperature at a
     depth of 50 cm below the soil surface is higher than 8 oC.          1. A mesic or thermic soil temperature regime and a
                                                 Udic Kandiustalfs       moisture control section that in normal years is dry in some
                                                                         part for 135 cumulative days or less per year when the soil
JCDI. Other Kandiustalfs that have, in all subhorizons in the            temperature at a depth of 50 cm below the soil surface is
upper 100 cm of the kandic horizon or throughout the entire              higher than 5 oC; or
kandic horizon if less than 100 cm thick, more than 50 percent
                                                                         2. A hyperthermic, isomesic, or warmer iso soil
colors that have all of the following:
                                                                         temperature regime and a moisture control section that in
     1.    Hue of 2.5YR or redder; and                                   normal years is dry in some or all parts for less than 120
Alfisols                                                                                                                              65



   cumulative days per year when the soil temperature at a                     a depth of 50 cm below the soil surface is higher than
   depth of 50 cm below the soil surface is higher than 8 oC.                  5 oC; and
                                           Udic Kanhaplustalfs
                                                                         3. One or both of the following:
JCEE. Other Kanhaplustalfs that have, in all subhorizons in                a. Cracks within 125 cm of the mineral soil surface that
the upper 100 cm of the kandic horizon or throughout the entire            are 5 mm or more wide through a thickness of 30 cm or
kandic horizon if less than 100 cm thick, more than 50 percent             more for some time in normal years and slickensides or
colors that have all of the following:                                     wedge-shaped peds in a layer 15 cm or more thick that
                                                                           has its upper boundary within 125 cm of the mineral soil
   1.    Hue of 2.5YR or redder; and
                                                                           surface; or
   2. Value, moist, of 3 or less; and                                                                                                      A
                                                                           b. A linear extensibility of 6.0 cm or more between             L
   3. Dry value no more than 1 unit higher than the moist                  the mineral soil surface and either a depth of 100 cm           F
   value.                                                                  or a densic, lithic, or paralithic contact, whichever is
                                      Rhodic Kanhaplustalfs                shallower.
                                                                                                           Leptic Torrertic Natrustalfs
JCEF.      Other Kanhaplustalfs.
                                             Typic Kanhaplustalfs      JCCC.   Other Natrustalfs that have both of the following:
                                                                         1. When neither irrigated nor fallowed to store moisture,
Natrustalfs                                                              one of the following:
Key to Subgroups                                                           a. A frigid soil temperature regime and a moisture
JCCA. Natrustalfs that have a salic horizon within 75 cm of                control section that in normal years is dry in all parts for
the mineral soil surface.                                                  four-tenths or more of the cumulative days per year when
                                           Salidic Natrustalfs             the soil temperature at a depth of 50 cm below the soil
                                                                           surface is higher than 5 oC; or
JCCB. Other Natrustalfs that have all of the following:                    b. A mesic or thermic soil temperature regime and a
   1. Visible crystals of gypsum or other salts more soluble               moisture control section that in normal years is dry in
   than gypsum, or both, within 40 cm of the soil surface; and             some part for six-tenths or more of the cumulative days
                                                                           per year when the soil temperature at a depth of 50 cm
   2. When neither irrigated nor fallowed to store moisture,               below the soil surface is higher than 5 oC; or
   one of the following:
                                                                           c. A hyperthermic, isomesic, or warmer iso soil
        a. A frigid soil temperature regime and a moisture
                                                                           temperature regime and a moisture control section that in
        control section that in normal years is dry in all parts for
                                                                           normal years:
        four-tenths or more of the cumulative days per year when
        the soil temperature at a depth of 50 cm below the soil                (1) Is moist in some or all parts for less than 90
        surface is higher than 5 oC; or                                        consecutive days per year when the temperature at a
                                                                               depth of 50 cm below the soil surface is higher than
        b. A mesic or thermic soil temperature regime and a
                                                                               8 oC; and
        moisture control section that in normal years is dry in
        some part for six-tenths or more of the cumulative days                (2) Is dry in some part for six-tenths or more of the
        per year when the soil temperature at a depth of 50 cm                 cumulative days per year when the soil temperature at
        below the soil surface is higher than 5 oC; or                         a depth of 50 cm below the soil surface is higher than
                                                                               5 oC; and
        c. A hyperthermic, isomesic, or warmer iso soil
        temperature regime and a moisture control section that in        2. One or both of the following:
        normal years:
                                                                           a. Cracks within 125 cm of the mineral soil surface that
           (1) Is moist in some or all parts for less than 90              are 5 mm or more wide through a thickness of 30 cm or
           consecutive days per year when the temperature at a             more for some time in normal years and slickensides or
           depth of 50 cm below the soil surface is higher than            wedge-shaped peds in a layer 15 cm or more thick that
           8 oC; and                                                       has its upper boundary within 125 cm of the mineral soil
                                                                           surface; or
           (2) Is dry in some part for six-tenths or more of the
           cumulative days per year when the soil temperature at           b. A linear extensibility of 6.0 cm or more between the
66                                                                                                                    Keys to Soil Taxonomy



          mineral soil surface and either a depth of 100 cm or a           JCCF. Other Natrustalfs that have one or both of the
          densic, lithic, or paralithic contact, whichever is shallower.   following:
                                                  Torrertic Natrustalfs
                                                                              1. Cracks within 125 cm of the mineral soil surface that are
                                                                              5 mm or more wide through a thickness of 30 cm or more
JCCD. Other Natrustalfs that have both:
                                                                              for some time in normal years and slickensides or wedge-
     1. In one or more horizons within 75 cm of the mineral soil              shaped peds in a layer 15 cm or more thick that has its upper
     surface, redox depletions with chroma of 2 or less and also              boundary within 125 cm of the mineral soil surface; or
     aquic conditions for some time in normal years (or artificial
                                                                              2. A linear extensibility of 6.0 cm or more between the
     drainage); and
                                                                              mineral soil surface and either a depth of 100 cm or a densic,
     2.    One or both of the following:                                      lithic, or paralithic contact, whichever is shallower.
                                                                                                                            Vertic Natrustalfs
          a. Cracks within 125 cm of the mineral soil surface that
          are 5 mm or more wide through a thickness of 30 cm or
          more for some time in normal years and slickensides or           JCCG. Other Natrustalfs that:
          wedge-shaped peds in a layer 15 cm or more thick that
                                                                              1. In one or more horizons within 75 cm of the mineral
          has its upper boundary within 125 cm of the mineral soil
                                                                              soil surface, have redox depletions with chroma of 2 or less
          surface; or
                                                                              and also aquic conditions for some time in normal years (or
          b. A linear extensibility of 6.0 cm or more between the             artificial drainage); and
          mineral soil surface and either a depth of 100 cm or a
                                                                              2. Meet sandy or sandy-skeletal particle-size class criteria
          densic, lithic, or paralithic contact, whichever is shallower.
                                                                              throughout a layer extending from the mineral soil surface to
                                                  Aquertic Natrustalfs
                                                                              the top of an argillic horizon at a depth of 50 cm or more.
                                                                                                                   Aquic Arenic Natrustalfs
JCCE. Other Natrustalfs that have both of the following:
     1. Visible crystals of gypsum or other salts more soluble
                                                                           JCCH. Other Natrustalfs that have, in one or more horizons
     than gypsum, or both, within 40 cm of the mineral soil
                                                                           within 75 cm of the mineral soil surface, redox depletions with
     surface; and
                                                                           chroma of 2 or less and also aquic conditions for some time in
     2. When neither irrigated nor fallowed to store moisture,             normal years (or artificial drainage).
     one of the following:                                                                                               Aquic Natrustalfs
          a. A frigid soil temperature regime and a moisture
          control section that in normal years is dry in all parts for     JCCI. Other Natrustalfs that meet sandy or sandy-skeletal
          four-tenths or more of the cumulative days per year when         particle-size class criteria throughout a layer extending from the
          the soil temperature at a depth of 50 cm below the soil          mineral soil surface to the top of an argillic horizon at a depth of
          surface is higher than 5 oC; or                                  50 cm or more.
                                                                                                                           Arenic Natrustalfs
          b. A mesic or thermic soil temperature regime and a
          moisture control section that in normal years is dry in
                                                                           JCCJ. Other Natrustalfs that have a petrocalcic horizon within
          some part for six-tenths or more of the cumulative days
                                                                           150 cm of the mineral soil surface.
          per year when the soil temperature at a depth of 50 cm
                                                                                                                 Petrocalcic Natrustalfs
          below the soil surface is higher than 5 oC; or
          c. A hyperthermic, isomesic, or warmer iso soil                  JCCK. Other Natrustalfs that have visible crystals of gypsum
          temperature regime and a moisture control section that in        or other salts more soluble than gypsum, or both, within 40 cm
          normal years:                                                    of the mineral soil surface.
                                                                                                                        Leptic Natrustalfs
             (1) Is moist in some or all parts for less than 90
             consecutive days per year when the temperature at a
                                                                           JCCL. Other Natrustalfs that have both of the following:
             depth of 50 cm below the soil surface is higher than
             8 oC; and                                                        1. An exchangeable sodium percentage of less than 15 (or
                                                                              a sodium adsorption ratio of less than 13) in 50 percent or
             (2) Is dry in some part for six-tenths or more of the
                                                                              more of the natric horizon; and
             cumulative days per year when the soil temperature at
             a depth of 50 cm below the soil surface is higher than           2. When neither irrigated nor fallowed to store moisture,
             5 oC.                                                            one of the following:
                                         Aridic Leptic Natrustalfs
Alfisols                                                                                                                            67



      a. A frigid soil temperature regime and a moisture               2. A glossic horizon or interfingering of albic materials into
      control section that in normal years is dry in all parts for     the natric horizon.
      four-tenths or more of the cumulative days per year when                                          Aridic Glossic Natrustalfs
      the soil temperature at a depth of 50 cm below the soil
      surface is higher than 5 oC; or                                JCCN. Other Natrustalfs that, when neither irrigated nor
                                                                     fallowed to store moisture, have one of the following:
      b. A mesic or thermic soil temperature regime and a
      moisture control section that in normal years is dry in          1. A frigid soil temperature regime and a moisture control
      some part for six-tenths or more of the cumulative days          section that in normal years is dry in all parts for four-
      per year when the soil temperature at a depth of 50 cm           tenths or more of the cumulative days per year when the soil
      below the soil surface is higher than 5 oC; or                   temperature at a depth of 50 cm below the soil surface is
                                                                       higher than 5 oC; or                                              A
      c. A hyperthermic, isomesic, or warmer iso soil                                                                                    L
                                                                                                                                         F
      temperature regime and a moisture control section that in        2. A mesic or thermic soil temperature regime and a
      normal years:                                                    moisture control section that in normal years is dry in some
                                                                       part for six-tenths or more of the cumulative days per year
           (1) Is moist in some or all parts for less than 90
                                                                       when the soil temperature at a depth of 50 cm below the soil
           consecutive days per year when the soil temperature at
                                                                       surface is higher than 5 oC; or
           a depth of 50 cm below the soil surface is higher than
           8 oC; and                                                   3. A hyperthermic, isomesic, or warmer iso soil
                                                                       temperature regime and a moisture control section that in
           (2) Is dry in some part for six-tenths or more of the
                                                                       normal years:
           cumulative days per year when the soil temperature at
           a depth of 50 cm below the soil surface is higher than           a. Is moist in some or all parts for less than 90
           5 oC.                                                            consecutive days per year when the soil temperature at a
                                         Haplargidic Natrustalfs            depth of 50 cm below the soil surface is higher than 8 oC;
                                                                            and
JCCM. Other Natrustalfs that have both:
                                                                            b. Is dry in some part for six-tenths or more of the
   1. When neither irrigated nor fallowed to store moisture, one            cumulative days per year when the soil temperature at a
   of the following:                                                        depth of 50 cm below the soil surface is higher than 5 oC.
                                                                                                                   Aridic Natrustalfs
      a. A frigid soil temperature regime and a moisture
      control section that in normal years is dry in all parts for
                                                                     JCCO. Other Natrustalfs that have a mollic epipedon, or the
      four-tenths or more of the cumulative days per year when
                                                                     upper 18 cm of the mineral soil meets the color requirements for
      the soil temperature at a depth of 50 cm below the soil
                                                                     a mollic epipedon after mixing.
      surface is higher than 5 °C; or
                                                                                                                  Mollic Natrustalfs
      b. A mesic or thermic soil temperature regime and a
      moisture control section that, in 6 normal years, is dry in    JCCP. Other Natrustalfs.
      some part for six-tenths or more of the cumulative days                                                       Typic Natrustalfs
      per year when the soil temperature at a depth of 50 cm
      below the soil surface is higher than 5 °C; or                 Paleustalfs
      c. A hyperthermic, isomesic, or warmer iso soil                Key to Subgroups
      temperature regime and a moisture control section that, in
                                                                     JCFA.    Paleustalfs that have both:
      normal years:
                                                                       1.    One or both of the following:
           (1) Is moist in some or all parts for less than 90
           consecutive days per year when the soil temperature at           a. Cracks within 125 cm of the mineral soil surface that
           a depth of 50 cm below the soil surface is higher than           are 5 mm or more wide through a thickness of 30 cm or
           8 °C; and                                                        more for some time in normal years and slickensides or
                                                                            wedge-shaped peds in a layer 15 cm or more thick that
           (2) Is dry in some part for six-tenths or more of the
                                                                            has its upper boundary within 125 cm of the mineral soil
           cumulative days per year when the soil temperature at
                                                                            surface; or
           a depth of 50 cm below the soil surface is higher than
           5 °C; and                                                        b. A linear extensibility of 6.0 cm or more between
68                                                                                                                 Keys to Soil Taxonomy



          the mineral soil surface and either a depth of 100 cm               has its upper boundary within 125 cm of the mineral soil
          or a densic, lithic, or paralithic contact, whichever is            surface; or
          shallower; and
                                                                              b. A linear extensibility of 6.0 cm or more between the
     2. In one or more horizons within 75 cm of the mineral soil              mineral soil surface and either a depth of 100 cm or a
     surface, redox depletions with chroma of 2 or less and also              densic, lithic, or paralithic contact, whichever is shallower.
     aquic conditions for some time in normal years (or artificial                                                     Udertic Paleustalfs
     drainage).
                                            Aquertic Paleustalfs       JCFD. Other Paleustalfs that have one or both of the
                                                                       following:
JCFB. Other Paleustalfs that have both:
                                                                         1. Cracks within 125 cm of the mineral soil surface that are
     1.    One or both of the following:                                 5 mm or more wide through a thickness of 30 cm or more
          a. Cracks within 125 cm of the mineral soil surface that       for some time in normal years and slickensides or wedge-
          are 5 mm or more wide through a thickness of 30 cm or          shaped peds in a layer 15 cm or more thick that has its upper
          more for some time in normal years and slickensides or         boundary within 125 cm of the mineral soil surface; or
          wedge-shaped peds in a layer 15 cm or more thick that          2. A linear extensibility of 6.0 cm or more between the
          has its upper boundary within 125 cm of the mineral soil       mineral soil surface and either a depth of 100 cm or a densic,
          surface; or                                                    lithic, or paralithic contact, whichever is shallower.
          b. A linear extensibility of 6.0 cm or more between                                                          Vertic Paleustalfs
          the mineral soil surface and either a depth of 100 cm
          or a densic, lithic, or paralithic contact, whichever is     JCFE.    Other Paleustalfs that:
          shallower; and                                                 1. In one or more horizons within 75 cm of the mineral
     2. Saturation with water in one or more layers within 100           soil surface, have redox depletions with chroma of 2 or less
     cm of the mineral soil surface in normal years for either or        and also aquic conditions for some time in normal years (or
     both:                                                               artificial drainage); and

          a.    20 or more consecutive days; or                          2. Meet sandy or sandy-skeletal particle-size class criteria
                                                                         throughout a layer extending from the mineral soil surface to
          b.    30 or more cumulative days.                              the top of an argillic horizon at a depth of 50 to 100 cm.
                                       Oxyaquic Vertic Paleustalfs                                             Aquic Arenic Paleustalfs
JCFC.          Other Paleustalfs that have both:                       JCFF. Other Paleustalfs that have, in one or more horizons
     1. When neither irrigated nor fallowed to store moisture,         within 75 cm of the mineral soil surface, redox depletions with
     either:                                                           chroma of 2 or less and also aquic conditions for some time in
                                                                       normal years (or artificial drainage).
          a. A mesic or thermic soil temperature regime and a                                                        Aquic Paleustalfs
          moisture control section that in normal years is dry in
          some part for four-tenths or less of the time (cumulative)   JCFG. Other Paleustalfs that are saturated with water in one or
          per year when the soil temperature at a depth of 50 cm       more layers within 100 cm of the mineral soil surface in normal
          below the soil surface is higher than 5 oC; or               years for either or both:
          b. A hyperthermic, isomesic, or warmer iso soil                1.    20 or more consecutive days; or
          temperature regime and a moisture control section that in
          normal years is dry in some or all parts for less than 120     2.    30 or more cumulative days.
          cumulative days per year when the soil temperature at a                                                   Oxyaquic Paleustalfs
          depth of 50 cm below the soil surface is higher than 8 oC;
          and                                                          JCFH. Other Paleustalfs that have an argillic horizon that
                                                                       meets one of the following:
     2.    One or both of the following:
                                                                         1.    Consists entirely of lamellae; or
          a. Cracks within 125 cm of the mineral soil surface that
          are 5 mm or more wide through a thickness of 30 cm or          2. Is a combination of two or more lamellae and one or
          more for some time in normal years and slickensides or         more subhorizons with a thickness of 7.5 to 20 cm, each
          wedge-shaped peds in a layer 15 cm or more thick that          layer with an overlying eluvial horizon; or
Alfisols                                                                                                                               69



   3. Consists of one or more subhorizons that are more than          mineral soil surface to the top of an argillic horizon at a depth of
   20 cm thick, each with an overlying eluvial horizon, and           100 cm or more.
   above these horizons there are either:                                                                      Grossarenic Paleustalfs
      a. Two or more lamellae with a combined thickness of
                                                                      JCFL. Other Paleustalfs that meet sandy or sandy-skeletal
      5 cm or more (that may or may not be part of the argillic
                                                                      particle-size class criteria throughout a layer extending from the
      horizon); or
                                                                      mineral soil surface to the top of an argillic horizon at a depth of
      b. A combination of lamellae (that may or may not be            50 to 100 cm.
      part of the argillic horizon) and one or more parts of the                                                      Arenic Paleustalfs
      argillic horizon 7.5 to 20 cm thick, each with an overlying
      eluvial horizon.                                                JCFM. Other Paleustalfs that have 5 percent or more (by                A
                                             Lamellic Paleustalfs     volume) plinthite in one or more horizons within 150 cm of the         L
                                                                                                                                             F
                                                                      mineral soil surface.
JCFI. Other Paleustalfs that have a sandy particle-size class                                                    Plinthic Paleustalfs
throughout the upper 75 cm of the argillic horizon or throughout
the entire argillic horizon if it is less than 75 cm thick.           JCFN. Other Paleustalfs that have a petrocalcic horizon within
                                             Psammentic Paleustalfs   150 cm of the mineral soil surface.
                                                                                                            Petrocalcic Paleustalfs
JCFJ. Other Paleustalfs that:
                                                                      JCFO. Other Paleustalfs that have both:
   1. Meet sandy or sandy-skeletal particle-size class criteria
   throughout a layer extending from the mineral soil surface to         1. When neither irrigated nor fallowed to store moisture,
   the top of an argillic horizon at a depth of 50 to 100 cm; and        either:
   2. When neither irrigated nor fallowed to store moisture,                a. A frigid soil temperature regime and a moisture
   have one of the following:                                               control section that in normal years is dry in all parts
                                                                            for four-tenths or more of the time (cumulative) per year
      a. A frigid soil temperature regime and a moisture
                                                                            when the soil temperature at a depth of 50 cm below the
      control section that in normal years is dry in all parts
                                                                            soil surface is higher than 5 oC; or
      for four-tenths or more of the time (cumulative) per year
      when the soil temperature at a depth of 50 cm below the               b. A mesic or thermic soil temperature regime and a
      soil surface is higher than 5 oC; or                                  moisture control section that in normal years is dry in
                                                                            some part for six-tenths or more of the time (cumulative)
      b. A mesic or thermic soil temperature regime and a
                                                                            per year when the soil temperature at a depth of 50 cm
      moisture control section that in normal years is dry in
                                                                            below the soil surface is higher than 5 oC; or
      some part for six-tenths or more of the time (cumulative)
      per year when the soil temperature at a depth of 50 cm                c. A hyperthermic, isomesic, or warmer iso soil
      below the soil surface is higher than 5 oC; or                        temperature regime and a moisture control section that in
                                                                            normal years:
      c. A hyperthermic, isomesic, or warmer iso soil
      temperature regime and a moisture control section that in                (1) Is moist in some or all parts for less than 90
      normal years:                                                            consecutive days per year when the soil temperature at
                                                                               a depth of 50 cm below the soil surface is higher than
           (1) Is moist in some or all parts for less than 90
                                                                               8 oC; and
           consecutive days per year when the soil temperature at
           a depth of 50 cm below the soil surface is higher than              (2) Is dry in some part for six-tenths or more of the
           8 oC; and                                                           cumulative days per year when the soil temperature at
                                                                               a depth of 50 cm below the soil surface is higher than
           (2) Is dry in some part for six-tenths or more of the
                                                                               5 oC; and
           cumulative days per year when the soil temperature at
           a depth of 50 cm below the soil surface is higher than        2. A calcic horizon either within 100 cm of the mineral
           5 oC.                                                         soil surface if the weighted average particle-size class of
                                       Arenic Aridic Paleustalfs         the upper 50 cm of the argillic horizon is sandy, or within
                                                                         60 cm if it is loamy, or within 50 cm if it is clayey, and free
JCFK. Other Paleustalfs that meet sandy or sandy-skeletal                carbonates in all horizons above the calcic horizon.
particle-size class criteria throughout a layer extending from the                                                  Calcidic Paleustalfs
70                                                                                                                Keys to Soil Taxonomy



JCFP. Other Paleustalfs that, when neither irrigated nor                   1. A mesic or thermic soil temperature regime and a
fallowed to store moisture, have:                                          moisture control section that in normal years is dry in some
                                                                           part for four-tenths or less of the time (cumulative) per year
     1. A frigid soil temperature regime and a moisture control
                                                                           when the soil temperature at a depth of 50 cm below the soil
     section that in normal years is dry in all parts for four-tenths
                                                                           surface is higher than 5 oC; or
     or more of the time (cumulative) per year when the soil
     temperature at a depth of 50 cm below the soil surface is             2. A hyperthermic, isomesic, or warmer iso soil
     higher than 5 oC; or                                                  temperature regime and a moisture control section that in
                                                                           normal years is dry in some or all parts for less than 120
     2. A mesic or thermic soil temperature regime and a
                                                                           cumulative days per year when the soil temperature at a
     moisture control section that in normal years is dry in some
                                                                           depth of 50 cm below the soil surface is higher than 8 oC.
     part for six-tenths or more of the time (cumulative) per year
                                                                                                                         Udic Paleustalfs
     when the soil temperature at a depth of 50 cm below the soil
     surface is higher than 5 oC; or
                                                                        JCFU.   Other Paleustalfs.
     3. A hyperthermic, isomesic, or warmer iso soil                                                                   Typic Paleustalfs
     temperature regime and a moisture control section that in
     normal years:                                                      Plinthustalfs
          a. Is moist in some or all parts for less than 90             Key to Subgroups
          consecutive days per year when the soil temperature at a
          depth of 50 cm below the soil surface is higher than 8 oC;    JCBA. All Plinthustalfs (provisionally).
          and                                                                                                        Typic Plinthustalfs
          b. Is dry in some part for six-tenths or more of the
          cumulative days per year when the soil temperature at         Rhodustalfs
          a depth of 50 cm below the soil surface is higher than        Key to Subgroups
          5 oC.
                                                  Aridic Paleustalfs    JCGA. Rhodustalfs that have a lithic contact within 50 cm of
                                                                        the mineral soil surface.
JCFQ. Other Paleustalfs that have a CEC of less than 24                                                           Lithic Rhodustalfs
cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more
either of the argillic horizon if less than 100 cm thick or of its      JCGB. Other Rhodustalfs that have a CEC of less than 24
upper 100 cm.                                                           cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more
                                                Kandic Paleustalfs      either of the argillic horizon if less than 100 cm thick or of its
                                                                        upper 100 cm.
JCFR. Other Paleustalfs that have, in all subhorizons in the                                                        Kanhaplic Rhodustalfs
upper 100 cm of the argillic horizon or throughout the entire
argillic horizon if less than 100 cm thick, more than 50 percent        JCGC. Other Rhodustalfs that, when neither irrigated nor
colors that have all of the following:                                  fallowed to store moisture, have either:

     1.    Hue of 2.5YR or redder; and                                     1. A mesic or thermic soil temperature regime and a
                                                                           moisture control section that in normal years is dry in some
     2. Value, moist, of 3 or less; and                                    part for four-tenths or less of the time (cumulative) per year
     3. Dry value no more than 1 unit higher than the moist                when the soil temperature at a depth of 50 cm below the soil
     value.                                                                surface is higher than 5 oC; or
                                            Rhodic Paleustalfs
                                                                           2. A hyperthermic, isomesic, or warmer iso soil
                                                                           temperature regime and a moisture control section that in
JCFS. Other Paleustalfs that have an argillic horizon with
                                                                           normal years is dry in some or all parts for less than 120
a base saturation (by sum of cations) of less than 75 percent
                                                                           cumulative days per year when the soil temperature at a
throughout.
                                                                           depth of 50 cm below the soil surface is higher than 8 oC.
                                                 Ultic Paleustalfs
                                                                                                                        Udic Rhodustalfs

JCFT. Other Paleustalfs that, when neither irrigated nor                JCGD.    Other Rhodustalfs.
fallowed to store moisture, have either:                                                                              Typic Rhodustalfs
Alfisols                                                                                                                               71




Xeralfs                                                                 3. No densic, lithic, or paralithic contact within 50 cm of
                                                                        the mineral soil surface and an argillic or kandic horizon that
Key to Great Groups                                                     has within 15 cm of its upper boundary both:

JDA. Xeralfs that have a duripan within 100 cm of the mineral                a.   35 percent or more noncarbonate clay; and
soil surface.                                                                b. A clay increase, in the fine-earth fraction, of either
                                           Durixeralfs, p. 71                20 percent or more (absolute) within a vertical distance
                                                                             of 7.5 cm or of 15 percent or more (absolute) within a
JDB.     Other Xeralfs that have a natric horizon.                           vertical distance of 2.5 cm.
                                                Natrixeralfs, p. 74                                                   Palexeralfs, p. 74
                                                                                                                                             A
JDC. Other Xeralfs that have a fragipan within 100 cm of the          JDG.    Other Xeralfs.                                                 L
                                                                                                                                             F
mineral soil surface.                                                                                                Haploxeralfs, p. 72
                                           Fragixeralfs, p. 72
                                                                      Durixeralfs
JDD. Other Xeralfs that have one or more horizons within 150
cm of the mineral soil surface in which plinthite either forms a      Key to Subgroups
continuous phase or constitutes one-half or more of the volume.       JDAA. Durixeralfs that have a natric horizon.
                                            Plinthoxeralfs, p. 76                                                Natric Durixeralfs

JDE. Other Xeralfs that have, in all subhorizons in the upper         JDAB. Other Durixeralfs that have, above the duripan, one or
100 cm of the argillic or kandic horizon or throughout the entire     both of the following:
argillic or kandic horizon if less than 100 cm thick, more than
50 percent colors that have all of the following:                       1. Cracks that are 5 mm or more wide through a thickness
                                                                        of 30 cm or more for some time in normal years and
   1.    Hue of 2.5YR or redder; and                                    slickensides or wedge-shaped peds in a layer 15 cm or more
   2. Value, moist, of 3 or less; and                                   thick; or

   3. Dry value no more than 1 unit higher than the moist               2. A linear extensibility of 6.0 cm or more.
   value.                                                                                                        Vertic Durixeralfs
                                         Rhodoxeralfs, p. 76
                                                                      JDAC. Other Durixeralfs that have, in one or more
JDF. Other Xeralfs that have one or more of the following:            subhorizons within the argillic horizon, redox depletions with
                                                                      chroma of 2 or less and also aquic conditions for some time in
   1. A petrocalcic horizon within 150 cm of the mineral soil         normal years (or artificial drainage).
   surface; or                                                                                                      Aquic Durixeralfs
   2. No densic, lithic, or paralithic contact within 150 cm of
   the mineral soil surface and an argillic or kandic horizon that    JDAD. Other Durixeralfs that have both:
   has both:
                                                                        1. An argillic horizon that has both:
        a. Within 150 cm of the mineral soil surface, either:
                                                                             a. A clayey particle-size class throughout some
           (1) With increasing depth, no clay decrease of 20                 subhorizon 7.5 cm or more thick; and
           percent or more (relative) from the maximum clay
           content [Clay is measured noncarbonate clay or is                 b. At its upper boundary or within some part, a clay
           based on the following formula: Clay % = 2.5(% water              increase either of 20 percent or more (absolute) within
           retained at 1500 kPa tension - % organic carbon),                 a vertical distance of 7.5 cm or of 15 percent or more
           whichever value is greater, but no more than 100]; or             (absolute) within a vertical distance of 2.5 cm, in the fine-
                                                                             earth fraction; and
           (2) 5 percent or more (by volume) skeletans on
                                                                        2. A duripan that is strongly cemented or less cemented in
           faces of peds in the layer that has a 20 percent lower
                                                                        all subhorizons.
           clay content and, below that layer, a clay increase of 3
                                                                                                       Abruptic Haplic Durixeralfs
           percent or more (absolute) in the fine-earth fraction;
           and
                                                                      JDAE. Other Durixeralfs that have an argillic horizon that has
        b. A base at a depth of 150 cm or more; or                    both:
72                                                                                                              Keys to Soil Taxonomy



     1. A clayey particle-size class throughout some subhorizon       within 40 cm of the mineral soil surface, redox depletions with
     7.5 cm or more thick; and                                        chroma of 2 or less and also aquic conditions for some time in
                                                                      normal years (or artificial drainage).
     2. At its upper boundary or within some part, a clay
                                                                                                                   Aquic Fragixeralfs
     increase either of 20 percent or more (absolute) within
     a vertical distance of 7.5 cm or of 15 percent or more
                                                                      JDCE. Other Fragixeralfs that, above the fragipan, do not have
     (absolute) within a vertical distance of 2.5 cm, in the fine-
                                                                      an argillic or kandic horizon with clay films on both vertical and
     earth fraction.
                                                                      horizontal faces of any peds.
                                              Abruptic Durixeralfs
                                                                                                                  Inceptic Fragixeralfs
JDAF. Other Durixeralfs that have a duripan that is strongly
                                                                      JDCF. Other Fragixeralfs.
cemented or less cemented in all subhorizons.
                                                                                                                   Typic Fragixeralfs
                                           Haplic Durixeralfs

JDAG.      Other Durixeralfs.                                         Haploxeralfs
                                               Typic Durixeralfs      Key to Subgroups
                                                                      JDGA. Haploxeralfs that have both:
Fragixeralfs
                                                                         1. A lithic contact within 50 cm of the mineral soil surface;
Key to Subgroups
                                                                         and
JDCA. Fragixeralfs that have, throughout one or more
                                                                         2. A color value, moist, of 3 or less and 0.7 percent or
horizons with a total thickness of 18 cm or more within 75 cm
                                                                         more organic carbon either throughout an Ap horizon or
of the mineral soil surface, a fine-earth fraction with both a bulk
                                                                         throughout the upper 10 cm of an A horizon.
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
                                                                                                          Lithic Mollic Haploxeralfs
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.
                                                                      JDGB. Other Haploxeralfs that have both:
                                                Andic Fragixeralfs
                                                                         1. A lithic contact within 50 cm of the mineral soil surface;
JDCB. Other Fragixeralfs that have, throughout one or more               and
horizons with a total thickness of 18 cm or more within 75 cm
                                                                         2. An argillic or kandic horizon that is discontinuous
of the mineral soil surface, one or both of the following:
                                                                         horizontally in each pedon.
     1. More than 35 percent (by volume) fragments coarser                                       Lithic Ruptic-Inceptic Haploxeralfs
     than 2.0 mm, of which more than 66 percent is cinders,
     pumice, and pumicelike fragments; or                             JDGC. Other Haploxeralfs that have a lithic contact within 50
                                                                      cm of the mineral soil surface.
     2. A fine-earth fraction containing 30 percent or more
                                                                                                               Lithic Haploxeralfs
     particles 0.02 to 2.0 mm in diameter; and
       a. In the 0.02 to 2.0 mm fraction, 5 percent or more           JDGD. Other Haploxeralfs that have one or both of the
       volcanic glass; and                                            following:
       b. [(Al plus 1/2 Fe, percent extracted by ammonium                1. Cracks within 125 cm of the mineral soil surface that are
       oxalate) times 60] plus the volcanic glass (percent) is           5 mm or more wide through a thickness of 30 cm or more
       equal to 30 or more.                                              for some time in normal years and slickensides or wedge-
                                          Vitrandic Fragixeralfs         shaped peds in a layer 15 cm or more thick that has its upper
                                                                         boundary within 125 cm of the mineral soil surface; or
JDCC. Other Fragixeralfs that have a color value, moist,
                                                                         2. A linear extensibility of 6.0 cm or more between the
of 3 or less and a color value, dry, of 5 or less (crushed and
                                                                         mineral soil surface and either a depth of 100 cm or a densic,
smoothed sample) either throughout the upper 18 cm of the
                                                                         lithic, or paralithic contact, whichever is shallower.
mineral soil (unmixed) or between the mineral soil surface and a
                                                                                                                     Vertic Haploxeralfs
depth of 18 cm after mixing.
                                                Mollic Fragixeralfs
                                                                      JDGE. Other Haploxeralfs that have both:
JDCD. Other Fragixeralfs that have, in one or more horizons              1.   In one or more horizons within 75 cm of the mineral soil
Alfisols                                                                                                                              73



   surface, redox depletions with chroma of 2 or less and also                or more thick that has its upper boundary within 100 cm
   aquic conditions for some time in normal years (or artificial              of the mineral soil surface; or
   drainage); and
                                                                              b. In 60 percent or more of the volume of a layer 15 cm
   2. Throughout one or more horizons with a total thickness                  or more thick; and
   of 18 cm or more within 75 cm of the mineral soil surface,
                                                                         2. Redox depletions with chroma of 2 or less in layers
   one or more of the following:
                                                                         that also have aquic conditions in normal years (or artificial
        a. A fine-earth fraction with both a bulk density of 1.0         drainage) either:
        g/cm3 or less, measured at 33 kPa water retention, and Al
                                                                              a. Within the upper 25 cm of the argillic or kandic
        plus 1/2 Fe percentages (by ammonium oxalate) totaling
                                                                              horizon if its upper boundary is within 50 cm of the
        more than 1.0; or                                                                                                                  A
                                                                              mineral soil surface; or                                     L
        b. More than 35 percent (by volume) fragments coarser                                                                              F
        than 2.0 mm, of which more than 66 percent is cinders,                b. Within 75 cm of the mineral soil surface if the upper
        pumice, and pumicelike fragments; or                                  boundary of the argillic or kandic horizon is 50 cm or
                                                                              more below the mineral soil surface.
        c. A fine-earth fraction containing 30 percent or more                                                 Fragiaquic Haploxeralfs
        particles 0.02 to 2.0 mm in diameter; and
             (1) In the 0.02 to 2.0 mm fraction, 5 percent or more     JDGI. Other Haploxeralfs that have both:
             volcanic glass; and                                         1. In one or more horizons within 75 cm of the mineral soil
             (2) [(Al plus 1/2 Fe, percent extracted by ammonium         surface, redox depletions with chroma of 2 or less and also
             oxalate) times 60] plus the volcanic glass (percent) is     aquic conditions for some time in normal years (or artificial
             equal to 30 or more.                                        drainage); and
                                            Aquandic Haploxeralfs        2. An argillic or kandic horizon that has a base saturation
                                                                         (by sum of cations) of less than 75 percent in one or more
JDGF. Other Haploxeralfs that have, throughout one or more               subhorizons within its upper 75 cm or above a densic, lithic,
horizons with a total thickness of 18 cm or more within 75 cm            or paralithic contact, whichever is shallower.
of the mineral soil surface, a fine-earth fraction with both a bulk                                             Aquultic Haploxeralfs
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling          JDGJ. Other Haploxeralfs that have, in one or more horizons
more than 1.0.                                                         within 75 cm of the mineral soil surface, redox depletions with
                                               Andic Haploxeralfs      chroma of 2 or less and also aquic conditions for some time in
                                                                       normal years (or artificial drainage).
JDGG. Other Haploxeralfs that have, throughout one or more                                                         Aquic Haploxeralfs
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:             JDGK. Other Haploxeralfs that have an exchangeable sodium
   1. More than 35 percent (by volume) fragments coarser               percentage of 15 or more (or a sodium adsorption ratio of 13
   than 2.0 mm, of which more than 66 percent is cinders,              or more) in one or more subhorizons of the argillic or kandic
   pumice, and pumicelike fragments; or                                horizon.
                                                                                                                 Natric Haploxeralfs
   2. A fine-earth fraction containing 30 percent or more
   particles 0.02 to 2.0 mm in diameter; and                           JDGL. Other Haploxeralfs that have fragic soil properties:
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more             1. In 30 percent or more of the volume of a layer 15 cm or
        volcanic glass; and                                              more thick that has its upper boundary within 100 cm of the
        b. [(Al plus 1/2 Fe, percent extracted by ammonium               mineral soil surface; or
        oxalate) times 60] plus the volcanic glass (percent) is
                                                                         2. In 60 percent or more of the volume of a layer 15 cm or
        equal to 30 or more.
                                                                         more thick.
                                           Vitrandic Haploxeralfs
                                                                                                               Fragic Haploxeralfs
JDGH.        Other Haploxeralfs that have both:
                                                                       JDGM. Other Haploxeralfs that have an argillic horizon that
   1.    Fragic soil properties:                                       meets one of the following:
        a.    In 30 percent or more of the volume of a layer 15 cm       1.    Consists entirely of lamellae; or
74                                                                                                               Keys to Soil Taxonomy



     2. Is a combination of two or more lamellae and one or           Natrixeralfs
     more subhorizons with a thickness of 7.5 to 20 cm, each
     layer with an overlying eluvial horizon; or                      Key to Subgroups

     3. Consists of one or more subhorizons that are more than        JDBA. Natrixeralfs that have one or both of the following:
     20 cm thick, each with an overlying eluvial horizon, and           1. Cracks within 125 cm of the mineral soil surface that are
     above these horizons there are either:                             5 mm or more wide through a thickness of 30 cm or more
        a. Two or more lamellae with a combined thickness of            for some time in normal years and slickensides or wedge-
        5 cm or more (that may or may not be part of the argillic       shaped peds in a layer 15 cm or more thick that has its upper
        horizon); or                                                    boundary within 125 cm of the mineral soil surface; or

        b. A combination of lamellae (that may or may not be            2. A linear extensibility of 6.0 cm or more between the
        part of the argillic horizon) and one or more parts of the      mineral soil surface and either a depth of 100 cm or a densic,
        argillic horizon 7.5 to 20 cm thick, each with an overlying     lithic, or paralithic contact, whichever is shallower.
        eluvial horizon.                                                                                             Vertic Natrixeralfs
                                            Lamellic Haploxeralfs
                                                                      JDBB. Other Natrixeralfs that have, in one or more horizons
JDGN. Other Haploxeralfs that have a sandy particle-size              within 75 cm of the mineral soil surface, redox depletions with
class throughout the upper 75 cm of the argillic horizon or           chroma of 2 or less and also aquic conditions for some time in
throughout the entire argillic horizon if it is less than 75 cm       normal years (or artificial drainage).
thick.                                                                                                             Aquic Natrixeralfs
                                      Psammentic Haploxeralfs
                                                                      JDBC. Other Natrixeralfs.
JDGO. Other Haploxeralfs that have 5 percent or more (by                                                            Typic Natrixeralfs
volume) plinthite in one or more horizons within 150 cm of the
mineral soil surface.                                                 Palexeralfs
                                         Plinthic Haploxeralfs        Key to Subgroups

JDGP. Other Haploxeralfs that have a calcic horizon within            JDFA.     Palexeralfs that have one or both of the following:
100 cm of the mineral soil surface.                                     1. Cracks within 125 cm of the mineral soil surface that are
                                         Calcic Haploxeralfs            5 mm or more wide through a thickness of 30 cm or more
                                                                        for some time in normal years and slickensides or wedge-
JDGQ.      Other Haploxeralfs that:                                     shaped peds in a layer 15 cm or more thick that has its upper
     1. Have an argillic or kandic horizon that is 35 cm or less        boundary within 125 cm of the mineral soil surface; or
     thick; and                                                         2. A linear extensibility of 6.0 cm or more between the
     2. Do not have a densic, lithic, or paralithic contact within      mineral soil surface and either a depth of 100 cm or a densic,
     100 cm of the mineral soil surface.                                lithic, or paralithic contact, whichever is shallower.
                                            Inceptic Haploxeralfs                                                     Vertic Palexeralfs

JDGR. Other Haploxeralfs that have an argillic or kandic              JDFB.     Other Palexeralfs that have both:
horizon that has a base saturation (by sum of cations) of less
                                                                        1. In one or more horizons within 75 cm of the mineral soil
than 75 percent in one or more subhorizons within its upper 75
                                                                        surface, redox depletions with chroma of 2 or less and also
cm or above a densic, lithic, or paralithic contact, whichever is
                                                                        aquic conditions for some time in normal years (or artificial
shallower.
                                                                        drainage); and
                                               Ultic Haploxeralfs
                                                                        2. Throughout one or more horizons with a total thickness
JDGS. Other Haploxeralfs that have a color value, moist, of 3           of 18 cm or more within 75 cm of the mineral soil surface,
or less and 0.7 percent or more organic carbon either throughout        one or more of the following:
the upper 10 cm of the mineral soil (unmixed) or throughout the
                                                                           a. A fine-earth fraction with both a bulk density of 1.0
upper 18 cm of the mineral soil after mixing.
                                                                           g/cm3 or less, measured at 33 kPa water retention, and Al
                                            Mollic Haploxeralfs
                                                                           plus 1/2 Fe percentages (by ammonium oxalate) totaling
                                                                           more than 1.0; or
JDGT.      Other Haploxeralfs.
                                              Typic Haploxeralfs           b.    More than 35 percent (by volume) fragments coarser
Alfisols                                                                                                                              75



        than 2.0 mm, of which more than 66 percent is cinders,                b. Within 75 cm of the mineral soil surface if the upper
        pumice, and pumicelike fragments; or                                  boundary of the argillic or kandic horizon is 50 cm or
                                                                              more below the mineral soil surface.
        c. A fine-earth fraction containing 30 percent or more
                                                                                                                 Fragiaquic Palexeralfs
        particles 0.02 to 2.0 mm in diameter; and
           (1) In the 0.02 to 2.0 mm fraction, 5 percent or more      JDFF. Other Palexeralfs that have, in one or more horizons
           volcanic glass; and                                        within 75 cm of the mineral soil surface, redox depletions with
                                                                      chroma of 2 or less and also aquic conditions for some time in
           (2) [(Al plus 1/2 Fe, percent extracted by ammonium
                                                                      normal years (or artificial drainage).
           oxalate) times 60] plus the volcanic glass (percent) is
                                                                                                                    Aquic Palexeralfs
           equal to 30 or more.
                                            Aquandic Palexeralfs                                                                            A
                                                                      JDFG. Other Palexeralfs that have a petrocalcic horizon               L
                                                                                                                                            F
                                                                      within 150 cm of the mineral soil surface.
JDFC. Other Palexeralfs that have, throughout one or more
                                                                                                              Petrocalcic Palexeralfs
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, a fine-earth fraction with both a bulk
                                                                      JDFH. Other Palexeralfs that have an argillic horizon that
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
                                                                      meets one of the following:
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
more than 1.0.                                                           1.    Consists entirely of lamellae; or
                                                 Andic Palexeralfs
                                                                         2. Is a combination of two or more lamellae and one or
                                                                         more subhorizons with a thickness of 7.5 to 20 cm, each
JDFD. Other Palexeralfs that have, throughout one or more
                                                                         layer with an overlying eluvial horizon; or
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:               3. Consists of one or more subhorizons that are more than
                                                                         20 cm thick, each with an overlying eluvial horizon, and
   1. More than 35 percent (by volume) fragments coarser
                                                                         above these horizons there are either:
   than 2.0 mm, of which more than 66 percent is cinders,
   pumice, and pumicelike fragments; or                                       a. Two or more lamellae with a combined thickness of
                                                                              5 cm or more (that may or may not be part of the argillic
   2. A fine-earth fraction containing 30 percent or more
                                                                              horizon); or
   particles 0.02 to 2.0 mm in diameter; and
                                                                              b. A combination of lamellae (that may or may not be
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                                                              part of the argillic horizon) and one or more parts of the
        volcanic glass; and
                                                                              argillic horizon 7.5 to 20 cm thick, each with an overlying
        b. [(Al plus 1/2 Fe, percent extracted by ammonium                    eluvial horizon.
        oxalate) times 60] plus the volcanic glass (percent) is                                                     Lamellic Palexeralfs
        equal to 30 or more.
                                             Vitrandic Palexeralfs    JDFI. Other Palexeralfs that have a sandy particle-size class
                                                                      throughout the upper 75 cm of the argillic horizon or throughout
JDFE.      Other Palexeralfs that have both:                          the entire argillic horizon if it is less than 75 cm thick.
                                                                                                                  Psammentic Palexeralfs
   1.    Fragic soil properties:
        a. In 30 percent or more of the volume of a layer 15 cm       JDFJ. Other Palexeralfs that meet sandy or sandy-skeletal
        or more thick that has its upper boundary within 100 cm       particle-size class criteria throughout a layer extending from the
        of the mineral soil surface; or                               mineral soil surface to the top of an argillic or kandic horizon at
                                                                      a depth of 50 cm or more.
        b. In 60 percent or more of the volume of a layer 15 cm
                                                                                                                      Arenic Palexeralfs
        or more thick; and
   2. Redox depletions with chroma of 2 or less in layers
                                                                      JDFK. Other Palexeralfs that have an exchangeable sodium
   that also have aquic conditions in normal years (or artificial
                                                                      percentage of 15 or more (or a sodium adsorption ratio of 13 or
   drainage) either:
                                                                      more) in one or more horizons within 100 cm of the mineral soil
        a. Within the upper 25 cm of the argillic or kandic           surface.
        horizon if its upper boundary is within 50 cm of the                                                      Natric Palexeralfs
        mineral soil surface; or
76



JDFL.     Other Palexeralfs that have fragic soil properties:         Plinthoxeralfs
     1. In 30 percent or more of the volume of a layer 15 cm or       Key to Subgroups
     more thick that has its upper boundary within 100 cm of the
     mineral soil surface; or                                         JDDA. All Plinthoxeralfs (provisionally).
                                                                                                               Typic Plinthoxeralfs
     2. In 60 percent or more of the volume of a layer 15 cm or
     more thick.                                                      Rhodoxeralfs
                                             Fragic Palexeralfs
                                                                      Key to Subgroups
JDFM. Other Palexeralfs that have a calcic horizon within 150         JDEA. Rhodoxeralfs that have a lithic contact within 50 cm of
cm of the mineral soil surface.                                       the mineral soil surface.
                                           Calcic Palexeralfs                                                 Lithic Rhodoxeralfs

JDFN. Other Palexeralfs that have 5 percent or more (by               JDEB. Other Rhodoxeralfs that have one or both of the
volume) plinthite in one or more horizons within 150 cm of the        following:
mineral soil surface.
                                           Plinthic Palexeralfs         1. Cracks within 125 cm of the mineral soil surface that are
                                                                        5 mm or more wide through a thickness of 30 cm or more
JDFO. Other Palexeralfs that have an argillic or kandic                 for some time in normal years and slickensides or wedge-
horizon that has a base saturation (by sum of cations) of less          shaped peds in a layer 15 cm or more thick that has its upper
than 75 percent throughout.                                             boundary within 125 cm of the mineral soil surface; or
                                                Ultic Palexeralfs       2. A linear extensibility of 6.0 cm or more between the
                                                                        mineral soil surface and either a depth of 100 cm or a densic,
JDFP. Other Palexeralfs with an argillic or kandic horizon that         lithic, or paralithic contact, whichever is shallower.
has, in the fine-earth fraction, either or both:                                                                   Vertic Rhodoxeralfs
     1. Less than 35 percent clay throughout all subhorizons
     within 15 cm of its upper boundary; or                           JDEC. Other Rhodoxeralfs that have a petrocalcic horizon
                                                                      within 150 cm of the mineral soil surface.
     2. At its upper boundary, a clay increase of less than 20                                              Petrocalcic Rhodoxeralfs
     percent (absolute) within a vertical distance of 7.5 cm and of
     less than 15 percent (absolute) within a vertical distance of    JDED. Other Rhodoxeralfs that have a calcic horizon within
     2.5 cm.                                                          150 cm of the mineral soil surface.
                                                Haplic Palexeralfs                                           Calcic Rhodoxeralfs

JDFQ. Other Palexeralfs that have a color value, moist, of 3 or       JDEE. Other Rhodoxeralfs that have an argillic or kandic
less and 0.7 percent or more organic carbon either throughout         horizon that is either less than 35 cm thick or is discontinuous
the upper 10 cm of the mineral soil (unmixed) or throughout the       horizontally in each pedon.
upper 18 cm of the mineral soil after mixing.                                                                    Inceptic Rhodoxeralfs
                                              Mollic Palexeralfs
                                                                      JDEF. Other Rhodoxeralfs.
JDFR.      Other Palexeralfs.                                                                                    Typic Rhodoxeralfs
                                                Typic Palexeralfs
                                                                                                                                          77




CHAPTER 6

                                                                                                                         Andisols

Key to Suborders                                                        layer with andic soil properties, whichever is shallower, and a
                                                                        densic, lithic, or paralithic contact, a duripan, or a petrocalcic
DA. Andisols that have either:                                          horizon.
  1. A histic epipedon; or                                                                                                Vitrands, p. 93
                                                                                                                                               A
  2. In a layer above a densic, lithic, or paralithic contact                                                                                  N
                                                                     DG. Other Andisols that have an ustic soil moisture regime.               D
  or in a layer at a depth between 40 and 50 cm either from                                                         Ustands, p. 92
  the mineral soil surface or from the top of an organic layer
  with andic soil properties, whichever is shallowest, aquic         DH. Other Andisols.
  conditions for some time in normal years (or artificial                                                                 Udands, p. 85
  drainage) and one or more of the following:
       a.   2 percent or more redox concentrations; or               Aquands
       b. A color value, moist, of 4 or more and 50 percent or
                                                                     Key to Great Groups
       more chroma of 2 or less either in redox depletions on
       faces of peds or in the matrix if peds are absent; or         DAA. Aquands that have a gelic soil temperature regime.
                                                                                                               Gelaquands, p. 79
       c. Enough active ferrous iron to give a positive reaction
       to alpha,alpha-dipyridyl at a time when the soil is not       DAB. Other Aquands that have a cryic soil temperature
       being irrigated.                                              regime.
                                                  Aquands, p. 77                                               Cryaquands, p. 78

DB. Other Andisols that have a gelic soil temperature regime.        DAC. Other Aquands that have, in half or more of each pedon,
                                               Gelands, p. 84        a placic horizon within 100 cm of the mineral soil surface or of
                                                                     the top of an organic layer with andic soil properties, whichever
DC. Other Andisols that have a cryic soil temperature regime.        is shallower.
                                              Cryands, p. 80                                                       Placaquands, p. 80

DD.    Other Andisols that have an aridic soil moisture regime.      DAD. Other Aquands that have, in 75 percent or more of
                                                 Torrands, p. 84     each pedon, a cemented horizon within 100 cm of the mineral
                                                                     soil surface or of the top of an organic layer with andic soil
DE.    Other Andisols that have a xeric soil moisture regime.        properties, whichever is shallower.
                                                  Xerands, p. 94                                                    Duraquands, p. 78

DF. Other Andisols that have a 1500 kPa water retention              DAE. Other Aquands that have a 1500 kPa water retention
of less than 15 percent on air-dried samples and less than 30        of less than 15 percent on air-dried samples and less than 30
percent on undried samples throughout 60 percent or more of          percent on undried samples throughout 60 percent or more of
the thickness either:                                                the thickness either:
  1. Within 60 cm of the mineral soil surface or of the top             1. Within 60 cm of the mineral soil surface or of the top
  of an organic layer with andic soil properties, whichever is          of an organic layer with andic soil properties, whichever is
  shallower, if there is no densic, lithic, or paralithic contact,      shallower, if there is no densic, lithic, or paralithic contact
  duripan, or petrocalcic horizon within that depth; or                 within that depth; or
  2.    Between the mineral soil surface or the top of an organic       2.   Between the mineral soil surface or the top of an organic
78                                                                                                               Keys to Soil Taxonomy



     layer with andic soil properties, whichever is shallower, and a   DADC. Other Duraquands that have, at a depth between 25
     densic, lithic, or paralithic contact.                            and 100 cm either from the mineral soil surface or from the
                                               Vitraquands, p. 80      top of an organic layer with andic soil properties, whichever
                                                                       is shallower, a layer 10 cm or more thick with more than 3.0
DAF.     Other Aquands that have a melanic epipedon.                   percent organic carbon and the colors of a mollic epipedon
                                          Melanaquands, p. 79          throughout, underlying one or more horizons with a total
                                                                       thickness of 10 cm or more that have a color value, moist, 1 unit
DAG. Other Aquands that have episaturation.                            or more higher and an organic-carbon content 1 percent or more
                                         Epiaquands, p. 79             (absolute) lower.
                                                                                                                  Thaptic Duraquands
DAH.      Other Aquands.
                                              Endoaquands, p. 78       DADD. Other Duraquands.
                                                                                                                    Typic Duraquands
Cryaquands
                                                                       Endoaquands
Key to Subgroups
                                                                       Key to Subgroups
DABA. Cryaquands that have a lithic contact within 50 cm
of the mineral soil surface or of the top of an organic layer with     DAHA. Endoaquands that have a lithic contact within 50 cm
andic soil properties, whichever is shallower.                         of the mineral soil surface or of the top of an organic layer with
                                               Lithic Cryaquands       andic soil properties, whichever is shallower.
                                                                                                                    Lithic Endoaquands
DABB.       Other Cryaquands that have a histic epipedon.
                                              Histic Cryaquands        DAHB. Other Endoaquands that have a horizon 15 cm or
                                                                       more thick that has 20 percent or more (by volume) cemented
DABC. Other Cryaquands that have, at a depth between 25                soil material within 100 cm of the mineral soil surface or of the
and 100 cm either from the mineral soil surface or from the            top of an organic layer with andic soil properties, whichever is
top of an organic layer with andic soil properties, whichever          shallower.
is shallower, a layer 10 cm or more thick with more than 3.0                                                       Duric Endoaquands
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total               DAHC. Other Endoaquands that have a histic epipedon.
thickness of 10 cm or more that have a color value, moist, 1 unit                                           Histic Endoaquands
or more higher and an organic-carbon content 1 percent or more
(absolute) lower.                                                      DAHD. Other Endoaquands that have more than 2.0
                                           Thaptic Cryaquands          cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one
                                                                       or more horizons with a total thickness of 10 cm or more at a
DABD. Other Cryaquands.                                                depth between 25 and 50 cm either from the mineral soil surface
                                               Typic Cryaquands        or from the top of an organic layer with andic soil properties,
                                                                       whichever is shallower.
Duraquands                                                                                                          Alic Endoaquands

Key to Subgroups                                                       DAHE. Other Endoaquands that have, on undried samples,
DADA.       Duraquands that have a histic epipedon.                    a 1500 kPa water retention of 70 percent or more throughout
                                              Histic Duraquands        a layer 35 cm or more thick within 100 cm of the mineral
                                                                       soil surface or of the top of an organic layer with andic soil
DADB. Other Duraquands that have a sum of extractable                  properties, whichever is shallower.
bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less                                                       Hydric Endoaquands
than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
horizons with a total thickness of 30 cm or more at a depth            DAHF. Other Endoaquands that have, at a depth between 25
between 25 and 100 cm either from the mineral soil surface             and 100 cm either from the mineral soil surface or from the
or from the top of an organic layer with andic soil properties,        top of an organic layer with andic soil properties, whichever
whichever is shallower.                                                is shallower, a layer 10 cm or more thick with more than 3.0
                                       Acraquoxic Duraquands           percent organic carbon and the colors of a mollic epipedon
Andisols                                                                                                                            79



throughout, underlying one or more horizons with a total            DAAB. Other Gelaquands that have gelic materials within 200
thickness of 10 cm or more that have a color value, moist, 1 unit   cm of the mineral soil surface.
or more higher and an organic-carbon content 1 percent or more                                             Turbic Gelaquands
(absolute) lower.
                                        Thaptic Endoaquands         DAAC. Other Gelaquands that have, at a depth between 25
                                                                    and 100 cm either from the mineral soil surface or from the
DAHG.      Other Endoaquands.                                       top of an organic layer with andic soil properties, whichever
                                           Typic Endoaquands        is shallower, a layer 10 cm or more thick with more than 3.0
                                                                    percent organic carbon and the colors of a mollic epipedon
Epiaquands                                                          throughout, underlying one or more horizons with a total
                                                                    thickness of 10 cm or more that have a color value, moist, 1 unit
Key to Subgroups
                                                                    or more higher and an organic-carbon content 1 percent or more
DAGA. Epiaquands that have a horizon 15 cm or more thick            (absolute) lower.
that has 20 percent or more (by volume) cemented soil material                                                  Thaptic Gelaquands
                                                                                                                                         A
within 100 cm of the mineral soil surface or of the top of an                                                                            N
organic layer with andic soil properties, whichever is shallower.   DAAD. Other Gelaquands.                                              D
                                              Duric Epiaquands                                                    Typic Gelaquands

DAGB. Other Epiaquands that have a histic epipedon.                 Melanaquands
                                         Histic Epiaquands
                                                                    Key to Subgroups
DAGC. Other Epiaquands that have more than 2.0                      DAFA. Melanaquands that have a lithic contact within 50 cm
cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one       of the mineral soil surface or of the top of an organic layer with
or more horizons with a total thickness of 10 cm or more at a       andic soil properties, whichever is shallower.
depth between 25 and 50 cm either from the mineral soil surface                                                 Lithic Melanaquands
or from the top of an organic layer with andic soil properties,
whichever is shallower.                                             DAFB. Other Melanaquands that have a sum of extractable
                                                Alic Epiaquands     bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less
                                                                    than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
DAGD. Other Epiaquands that have, on undried samples,               horizons with a total thickness of 30 cm or more at a depth
a 1500 kPa water retention of 70 percent or more throughout         between 25 and 100 cm either from the mineral soil surface
a layer 35 cm or more thick within 100 cm of the mineral            or from the top of an organic layer with andic soil properties,
soil surface or of the top of an organic layer with andic soil      whichever is shallower.
properties, whichever is shallower.                                                                      Acraquoxic Melanaquands
                                              Hydric Epiaquands
                                                                    DAFC. Other Melanaquands that have both:
DAGE. Other Epiaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the            1. On undried samples, a 1500 kPa water retention of 70
top of an organic layer with andic soil properties, whichever          percent or more throughout a layer 35 cm or more thick
is shallower, a layer 10 cm or more thick with more than 3.0           within 100 cm of the mineral soil surface or of the top of
percent organic carbon and the colors of a mollic epipedon             an organic layer with andic soil properties, whichever is
throughout, underlying one or more horizons with a total               shallower; and
thickness of 10 cm or more that have a color value, moist, 1 unit      2. More than 6.0 percent organic carbon and the colors of
or more higher and an organic-carbon content 1 percent or more         a mollic epipedon throughout a layer 50 cm or more thick
(absolute) lower.                                                      within 60 cm of the mineral soil surface or of the top of
                                            Thaptic Epiaquands         an organic layer with andic soil properties, whichever is
                                                                       shallower.
DAGF.      Other Epiaquands.                                                                         Hydric Pachic Melanaquands
                                             Typic Epiaquands
                                                                    DAFD. Other Melanaquands that have, on undried samples,
Gelaquands                                                          a 1500 kPa water retention of 70 percent or more throughout
                                                                    a layer 35 cm or more thick within 100 cm of the mineral
Key to Subgroups
                                                                    soil surface or of the top of an organic layer with andic soil
DAAA.      Gelaquands that have a histic epipedon.                  properties, whichever is shallower.
                                             Histic Gelaquands                                                 Hydric Melanaquands
80                                                                                                               Keys to Soil Taxonomy



DAFE. Other Melanaquands that have more than 6.0 percent               or more higher and an organic-carbon content 1 percent or more
organic carbon and the colors of a mollic epipedon throughout          (absolute) lower.
a layer 50 cm or more thick within 60 cm of the mineral                                                        Thaptic Placaquands
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.                                    DACF. Other Placaquands.
                                           Pachic Melanaquands                                                      Typic Placaquands

DAFF. Other Melanaquands that have, at a depth between                 Vitraquands
40 and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever          Key to Subgroups
is shallower, a layer 10 cm or more thick with more than 3.0           DAEA. Vitraquands that have a lithic contact within 50 cm
percent organic carbon and the colors of a mollic epipedon             of the mineral soil surface or of the top of an organic layer with
throughout, underlying one or more horizons with a total               andic soil properties, whichever is shallower.
thickness of 10 cm or more that have a color value, moist, 1 unit                                                     Lithic Vitraquands
or more higher and an organic-carbon content 1 percent or more
(absolute) lower.                                                      DAEB. Other Vitraquands that have a horizon 15 cm or more
                                         Thaptic Melanaquands          thick that has 20 percent or more (by volume) cemented soil
                                                                       material within 100 cm of the mineral soil surface or of the
DAFG. Other Melanaquands.                                              top of an organic layer with andic soil properties, whichever is
                                            Typic Melanaquands         shallower.
Placaquands                                                                                                         Duric Vitraquands

Key to Subgroups                                                       DAEC. Other Vitraquands that have a histic epipedon.
DACA. Placaquands that have a lithic contact within 50 cm                                                       Histic Vitraquands
of the mineral soil surface or of the top of an organic layer with
andic soil properties, whichever is shallower.                         DAED. Other Vitraquands that have, at a depth between 25
                                              Lithic Placaquands       and 100 cm either from the mineral soil surface or from the
                                                                       top of an organic layer with andic soil properties, whichever
DACB.      Other Placaquands that have both:                           is shallower, a layer 10 cm or more thick with more than 3.0
                                                                       percent organic carbon and the colors of a mollic epipedon
     1. A histic epipedon; and                                         throughout, underlying one or more horizons with a total
     2. A horizon 15 cm or more thick that has 20 percent or           thickness of 10 cm or more that have a color value, moist, 1 unit
     more (by volume) cemented soil material within 100 cm of          or more higher and an organic-carbon content 1 percent or more
     the mineral soil surface or of the top of an organic layer with   (absolute) lower.
     andic soil properties, whichever is shallower.                                                               Thaptic Vitraquands
                                         Duric Histic Placaquands
                                                                       DAEE. Other Vitraquands.
DACC. Other Placaquands that have a horizon 15 cm or more                                                           Typic Vitraquands
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface or of the           Cryands
top of an organic layer with andic soil properties, whichever is
shallower.                                                             Key to Great Groups
                                             Duric Placaquands         DCA. Cryands that have, in 75 percent or more of each pedon,
                                                                       a cemented horizon within 100 cm of the mineral soil surface
DACD. Other Placaquands that have a histic epipedon.                   or of the top of an organic layer with andic soil properties,
                                        Histic Placaquands             whichever is shallower.
                                                                                                                     Duricryands, p. 81
DACE. Other Placaquands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the            DCB. Other Cryands that have, on undried samples, a 1500
top of an organic layer with andic soil properties, whichever          kPa water retention of 100 percent or more, by weighted
is shallower, a layer 10 cm or more thick with more than 3.0           average, throughout either:
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total                  1. One or more layers with a total thickness of 35 cm
thickness of 10 cm or more that have a color value, moist, 1 unit         between the mineral soil surface or the top of an organic
Andisols                                                                                                                              81



  layer with andic soil properties, whichever is shallower,               to alpha,alpha-dipyridyl at a time when the soil is not being
  and 100 cm from the mineral soil surface or from the top                irrigated.
  of an organic layer with andic soil properties, whichever is                                                     Aquic Duricryands
  shallower, if there is no densic, lithic, or paralithic contact,
  duripan, or petrocalcic horizon within that depth; or                DCAB. Other Duricryands that have both:
  2. 60 percent or more of the horizon thickness between the              1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N
  mineral soil surface or the top of an organic layer with andic          KCl) in the fine-earth fraction and with a total thickness of
  soil properties, whichever is shallower, and a densic, lithic, or       10 cm or more at a depth between 25 and 50 cm either from
  paralithic contact, a duripan, or a petrocalcic horizon.                the mineral soil surface or from the top of an organic layer
                                            Hydrocryands, p. 83           with andic properties, whichever is shallower; and

DCC.    Other Cryands that have a melanic epipedon.                       2. Saturation with water in one or more layers above the
                                        Melanocryands, p. 83              cemented horizon in normal years for either or both:
                                                                               a.   20 or more consecutive days; or                         A
                                                                                                                                            N
DCD. Other Cryands that have a layer that meets the depth,                                                                                  D
thickness, and organic-carbon requirements for a melanic                       b.   30 or more cumulative days.
epipedon.                                                                                                Eutric Oxyaquic Duricryands
                                           Fulvicryands, p. 81
                                                                       DCAC. Other Duricryands that are saturated with water in one
DCE. Other Cryands that have a 1500 kPa water retention                or more layers above the cemented horizon in normal years for
of less than 15 percent on air-dried samples and less than 30          either or both:
percent on undried samples throughout 60 percent or more of               1.    20 or more consecutive days; or
the thickness either:
                                                                          2.    30 or more cumulative days.
  1. Within 60 cm of the mineral soil surface or of the top
                                                                                                                  Oxyaquic Duricryands
  of an organic layer with andic soil properties, whichever is
  shallower, if there is no densic, lithic, or paralithic contact,
                                                                       DCAD. Other Duricryands that have no horizons with more
  duripan, or petrocalcic horizon within that depth; or
                                                                       than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction
  2. Between the mineral soil surface or the top of an organic         and with a total thickness of 10 cm or more at a depth between
  layer with andic soil properties, whichever is shallower, and a      25 and 50 cm either from the mineral soil surface or from the
  densic, lithic, or paralithic contact, a duripan, or a petrocalcic   top of an organic layer with andic properties, whichever is
  horizon.                                                             shallower.
                                                Vitricryands, p. 83                                                Eutric Duricryands

DCF.   Other Cryands.                                                  DCAE. Other Duricryands.
                                              Haplocryands, p. 82                                                     Typic Duricryands

Duricryands                                                            Fulvicryands
Key to Subgroups                                                       Key to Subgroups
DCAA. Duricryands that have, in some subhorizon at a depth             DCDA. Fulvicryands that have a lithic contact within 50 cm
between 50 and 100 cm either from the mineral soil surface             of the mineral soil surface or of the top of an organic layer with
or from the top of an organic layer with andic soil properties,        andic soil properties, whichever is shallower.
whichever is shallower, aquic conditions for some time in                                                            Lithic Fulvicryands
normal years (or artificial drainage) and one or more of the
following:                                                             DCDB. Fulvicryands that have a folistic epipedon.
                                                                                                              Folistic Fulvicryands
  1.   2 percent or more redox concentrations; or
  2. A color value, moist, of 4 or more and 50 percent or              DCDC. Other Fulvicryands that have both:
  more chroma of 2 or less either in redox depletions on faces
                                                                          1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N
  of peds or in the matrix if peds are absent; or
                                                                          KCl) in the fine-earth fraction and with a total thickness of
  3.   Enough active ferrous iron to give a positive reaction             10 cm or more at a depth between 25 and 50 cm either from
82                                                                                                               Keys to Soil Taxonomy



     the mineral soil surface or from the top of an organic layer      soil surface or from the top of an organic layer with andic soil
     with andic properties, whichever is shallower; and                properties, whichever is shallower, aquic conditions for some
                                                                       time in normal years (or artificial drainage) and one or more of
     2. Throughout a layer 50 cm or more thick within 60 cm of
                                                                       the following:
     the mineral soil surface or of the top of an organic layer with
     andic properties, whichever is shallower:                            1.   2 percent or more redox concentrations; or
          a. More than 6.0 percent organic carbon, by weighted            2. A color value, moist, of 4 or more and 50 percent or
          average; and                                                    more chroma of 2 or less either in redox depletions on faces
                                                                          of peds or in the matrix if peds are absent; or
          b.   More than 4.0 percent organic carbon in all parts.
                                       Eutric Pachic Fulvicryands         3. Enough active ferrous iron to give a positive reaction
                                                                          to alpha,alpha-dipyridyl at a time when the soil is not being
DCDD. Other Fulvicryands that have no horizons with more                  irrigated.
than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction                                                  Aquic Haplocryands
and with a total thickness of 10 cm or more at a depth between
25 and 50 cm either from the mineral soil surface or from the          DCFD. Other Haplocryands that are saturated with water
top of an organic layer with andic properties, whichever is            within 100 cm of the mineral soil surface in normal years for
shallower.                                                             either or both:
                                            Eutric Fulvicryands
                                                                          1.   20 or more consecutive days; or
DCDE. Other Fulvicryands that have, throughout a layer 50                 2.   30 or more cumulative days.
cm or more thick within 60 cm of the mineral soil surface or of                                               Oxyaquic Haplocryands
the top of an organic layer with andic soil properties, whichever
is shallower:                                                          DCFE. Other Haplocryands that have more than 2.0
     1. More than 6.0 percent organic carbon, by weighted              cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one
     average; and                                                      or more horizons with a total thickness of 10 cm or more at a
                                                                       depth between 25 and 50 cm either from the mineral soil surface
     2.    More than 4.0 percent organic carbon in all parts.          or from the top of an organic layer with andic soil properties,
                                             Pachic Fulvicryands       whichever is shallower.
                                                                                                                    Alic Haplocryands
DCDF. Other Fulvicryands that have a 1500 kPa water
retention of less than 15 percent on air-dried samples and less        DCFF. Other Haplocryands that have an albic horizon
than 30 percent on undried samples throughout one or more              overlying a cambic horizon in 50 percent or more of each pedon
layers that have andic soil properties and have a total thickness      or have a spodic horizon in 50 percent or more of each pedon.
of 25 cm or more within 100 cm of the mineral soil surface                                                       Spodic Haplocryands
or of the top of an organic layer with andic soil properties,
whichever is shallower.                                                DCFG. Other Haplocryands that have a sum of extractable
                                              Vitric Fulvicryands      bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less
                                                                       than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
DCDG.          Other Fulvicryands.                                     horizons with a total thickness of 30 cm or more at a depth
                                               Typic Fulvicryands      between 25 and 100 cm either from the mineral soil surface
                                                                       or from the top of an organic layer with andic soil properties,
Haplocryands                                                           whichever is shallower.
                                                                                                              Acrudoxic Haplocryands
Key to Subgroups
DCFA. Haplocryands that have a lithic contact within 50 cm             DCFH. Other Haplocryands that have a 1500 kPa water
of the mineral soil surface or of the top of an organic layer with     retention of less than 15 percent on air-dried samples and less
andic soil properties, whichever is shallower.                         than 30 percent on undried samples throughout one or more
                                             Lithic Haplocryands       layers that have andic soil properties and have a total thickness
                                                                       of 25 cm or more within 100 cm of the mineral soil surface
DCFB. Other Haplocryands that have a folistic epipedon.                or of the top of an organic layer with andic soil properties,
                                    Folistic Haplocryands              whichever is shallower.
                                                                                                                    Vitric Haplocryands
DCFC. Other Haplocryands that have, in some subhorizon
at a depth between 50 and 100 cm either from the mineral               DCFI.    Other Haplocryands that have, at a depth between 25
Andisols                                                                                                                             83



and 100 cm either from the mineral soil surface or from the          or more higher and an organic-carbon content 1 percent or more
top of an organic layer with andic soil properties, whichever        (absolute) lower.
is shallower, a layer 10 cm or more thick with more than 3.0                                                Thaptic Hydrocryands
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total             DCBE. Other Hydrocryands.
thickness of 10 cm or more that have a color value, moist, 1 unit                                                Typic Hydrocryands
or more higher and an organic-carbon content 1 percent or more
(absolute) lower.                                                    Melanocryands
                                          Thaptic Haplocryands
                                                                     Key to Subgroups
DCFJ. Other Haplocryands that have a xeric soil moisture             DCCA. Melanocryands that have a lithic contact within 50 cm
regime.                                                              of the mineral soil surface or of the top of an organic layer that
                                       Xeric Haplocryands            has andic soil properties, whichever is shallower.
                                                                                                                Lithic Melanocryands       A
DCFK. Other Haplocryands.                                                                                                                  N
                                                                                                                                           D
                                            Typic Haplocryands       DCCB. Other Melanocryands that have a 1500 kPa water
                                                                     retention of less than 15 percent on air-dried samples and less
Hydrocryands                                                         than 30 percent on undried samples throughout one or more
                                                                     layers that have andic soil properties and have a total thickness
Key to Subgroups
                                                                     of 25 cm or more within 100 cm of the mineral soil surface
DCBA. Hydrocryands that have a lithic contact within 50 cm           or of the top of an organic layer with andic soil properties,
of the mineral soil surface or of the top of an organic layer with   whichever is shallower.
andic soil properties, whichever is shallower.                                                                  Vitric Melanocryands
                                             Lithic Hydrocryands
                                                                     DCCC. Other Melanocryands.
DCBB. Other Hydrocryands that have a placic horizon                                                            Typic Melanocryands
within 100 cm of the mineral soil surface or of the top of an
organic layer with andic soil properties, whichever is shallower.    Vitricryands
                                           Placic Hydrocryands
                                                                     Key to Subgroups
DCBC. Other Hydrocryands that have, in one or more                   DCEA. Vitricryands that have a lithic contact within 50 cm of
horizons at a depth between 50 and 100 cm either from the            the mineral soil surface or of the top of an organic layer that has
mineral soil surface or from the top of an organic layer with        andic soil properties, whichever is shallower.
andic soil properties, whichever is shallower, aquic conditions                                                    Lithic Vitricryands
for some time in normal years (or artificial drainage) and one or
more of the following:                                               DCEB. Other Vitricryands that have a folistic epipedon.
                                                                                                             Folistic Vitricryands
   1.   2 percent or more redox concentrations; or
   2. A color value, moist, of 4 or more and 50 percent              DCEC. Other Vitricryands that have, in one or more horizons
   or more chroma of 2 or less either in redox depletions            at a depth between 50 and 100 cm either from the mineral
   on faces of peds or in the matrix if peds are absent; or          soil surface or from the top of an organic layer with andic soil
                                                                     properties, whichever is shallower, aquic conditions for some
   3. Enough active ferrous iron to give a positive reaction
                                                                     time in normal years (or artificial drainage) and one or more of
   to alpha,alpha-dipyridyl at a time when the soil is not being
                                                                     the following:
   irrigated.
                                          Aquic Hydrocryands            1.   2 percent or more redox concentrations; or
                                                                        2. A color value, moist, of 4 or more and 50 percent or
DCBD. Other Hydrocryands that have, at a depth between
                                                                        more chroma of 2 or less either in redox depletions on faces
25 and 100 cm either from the mineral soil surface or from the
                                                                        of peds or in the matrix if peds are absent; or
top of an organic layer with andic soil properties, whichever
is shallower, a layer 10 cm or more thick with more than 3.0            3. Enough active ferrous iron to give a positive reaction
percent organic carbon and the colors of a mollic epipedon              to alpha,alpha-dipyridyl at a time when the soil is not being
throughout, underlying one or more horizons with a total                irrigated.
thickness of 10 cm or more that have a color value, moist, 1 unit                                                Aquic Vitricryands
84                                                                                                                   Keys to Soil Taxonomy



DCED. Other Vitricryands that are saturated with water in                Gelands
one or more layers within 100 cm of the mineral soil surface in
normal years for either or both:                                         Key to Great Groups
     1.   20 or more consecutive days; or                                DBA. All Gelands are considered Vitrigelands.
     2.   30 or more cumulative days.                                                                             Vitrigelands, p. 84
                                            Oxyaquic Vitricryands        Key to Subgroups
DCEE. Other Vitricryands that have an albic horizon                      DBAA. Vitrigelands that have a mollic or umbric epipedon.
overlying a cambic horizon in 50 percent or more of each pedon                                                    Humic Vitrigelands
or have a spodic horizon in 50 percent or more of each pedon.
                                           Spodic Vitricryands           DBAB. Other Vitrigelands that have gelic materials within
                                                                         200 cm of the mineral soil surface.
DCEF. Other Vitricryands that have, at a depth between 25                                                         Turbic Vitrigelands
and 100 cm either from the mineral soil surface or from the
top of an organic layer with andic soil properties, whichever            DBAC. Other Vitrigelands.
is shallower, a layer 10 cm or more thick with more than 3.0                                                             Typic Vitrigelands
percent organic carbon and the colors of a mollic epipedon
throughout, underlying one or more horizons with a total
thickness of 10 cm or more that have a color value, moist, 1 unit
                                                                         Torrands
or more higher and an organic-carbon content 1 percent or more           Key to Great Groups
(absolute) lower.
                                           Thaptic Vitricryands          DDA. Torrands that have, in 75 percent or more of each
                                                                         pedon, a cemented horizon within 100 cm of the mineral
DCEG. Other Vitricryands that have a xeric soil moisture                 soil surface or of the top of an organic layer with andic soil
regime and a mollic or umbric epipedon.                                  properties, whichever is shallower.
                                   Humic Xeric Vitricryands                                                            Duritorrands, p. 84

DCEH. Other Vitricryands that have a xeric soil moisture                 DDB. Other Torrands that have, on air-dried samples, a 1500
regime.                                                                  kPa water retention of less than 15 percent throughout 60
                                         Xeric Vitricryands              percent or more of the thickness either:

DCEI. Other Vitricryands that have both:                                    1. Within 60 cm of the mineral soil surface or of the top
                                                                            of an organic layer with andic soil properties, whichever is
     1. An argillic or kandic horizon within 125 cm of the                  shallower, if there is no densic, lithic, or paralithic contact,
     mineral soil surface or of the top of an organic layer with            duripan, or petrocalcic horizon within that depth; or
     andic soil properties, whichever is shallower; and
                                                                            2. Between the mineral soil surface or the top of an organic
     2. A base saturation (by sum of cations) of less than 35
                                                                            layer with andic soil properties, whichever is shallower, and a
     percent throughout the upper 50 cm or throughout the entire
                                                                            densic, lithic, or paralithic contact, a duripan, or a petrocalcic
     argillic or kandic horizon if it is less than 50 cm thick.
                                                                            horizon.
                                                    Ultic Vitricryands
                                                                                                                         Vitritorrands, p. 85
DCEJ. Other Vitricryands that have an argillic or kandic
horizon within 125 cm of the mineral soil surface or of the              DDC. Other Torrands.
top of an organic layer with andic soil properties, whichever is                                                       Haplotorrands, p. 85
shallower.
                                               Alfic Vitricryands        Duritorrands
                                                                         Key to Subgroups
DCEK. Other Vitricryands that have a mollic or umbric
epipedon.                                                                DDAA. Duritorrands that have a petrocalcic horizon within
                                       Humic Vitricryands                100 cm of the mineral soil surface.
                                                                                                             Petrocalcic Duritorrands
DCEL.       Other Vitricryands.
                                                Typic Vitricryands       DDAB. Other Duritorrands that have, on air-dried samples, a
Andisols                                                                                                                                  85



1500 kPa water retention of less than 15 percent throughout 60         more chroma of 2 or less either in redox depletions on faces
percent or more of the thickness either:                               of peds or in the matrix if peds are absent; or
  1. Between the mineral soil surface or the top of an organic         3. Enough active ferrous iron to give a positive reaction
  layer with andic soil properties, whichever is shallower, if         to alpha,alpha-dipyridyl at a time when the soil is not being
  there is no paralithic contact or duripan within that depth,         irrigated.
  and a point 60 cm below that depth; or                                                                        Aquic Vitritorrands

  2. Between the mineral soil surface or the top of an organic      DDBD. Other Vitritorrands that have a calcic horizon within
  layer with andic soil properties, whichever is shallower, and a   125 cm of the mineral soil surface.
  paralithic contact or a duripan.                                                                          Calcic Vitritorrands
                                           Vitric Duritorrands
                                                                    DDBE. Other Vitritorrands.
DDAC.      Other Duritorrands.                                                                                     Typic Vitritorrands
                                           Typic Duritorrands                                                                                  A
                                                                                                                                               N
Haplotorrands                                                       Udands                                                                     D


Key to Subgroups                                                    Key to Great Groups
DDCA. Haplotorrands that have a lithic contact within 50 cm         DHA. Udands that have, in half or more of each pedon, a
of the mineral soil surface.                                        placic horizon within 100 cm of the mineral soil surface or of
                                      Lithic Haplotorrands          the top of an organic layer with andic soil properties, whichever
                                                                    is shallower.
                                                                                                                   Placudands, p. 91
DDCB. Other Haplotorrands that have a horizon 15 cm or
more thick that has 20 percent or more (by volume) cemented
                                                                    DHB. Other Udands that have, in 75 percent or more of
soil material within 100 cm of the mineral soil surface.
                                                                    each pedon, a cemented horizon within 100 cm of the mineral
                                          Duric Haplotorrands
                                                                    soil surface or of the top of an organic layer with andic soil
                                                                    properties, whichever is shallower.
DDCC. Other Haplotorrands that have a calcic horizon within
                                                                                                                    Durudands, p. 86
125 cm of the mineral soil surface.
                                    Calcic Haplotorrands
                                                                    DHC. Other Udands that have a melanic epipedon.
                                                                                                           Melanudands, p. 90
DDCD.      Other Haplotorrands.
                                         Typic Haplotorrands
                                                                    DHD. Other Udands that have, on undried samples, a 1500
                                                                    kPa water retention of 100 percent or more, by weighted
Vitritorrands                                                       average, throughout either:
Key to Subgroups                                                       1. One or more layers with a total thickness of 35 cm
DDBA. Vitritorrands that have a lithic contact within 50 cm of         between the mineral soil surface or the top of an organic
the mineral soil surface.                                              layer with andic soil properties, whichever is shallower,
                                         Lithic Vitritorrands          and 100 cm from the mineral soil surface or from the top
                                                                       of an organic layer with andic soil properties, whichever is
                                                                       shallower, if there is no densic, lithic, or paralithic contact,
DDBB. Other Vitritorrands that have a horizon 15 cm or more
                                                                       duripan, or petrocalcic horizon within that depth; or
thick that has 20 percent or more (by volume) cemented soil
material within 100 cm of the mineral soil surface.                    2. 60 percent or more of the horizon thickness between the
                                            Duric Vitritorrands        mineral soil surface or the top of an organic layer with andic
                                                                       soil properties, whichever is shallower, and a densic, lithic, or
DDBC. Other Vitritorrands that have, in one or more horizons           paralithic contact, a duripan, or a petrocalcic horizon.
at a depth between 50 and 100 cm from the mineral soil surface,                                                    Hydrudands, p. 89
aquic conditions for some time in normal years (or artificial
drainage) and one or more of the following:                         DHE. Other Udands that have a layer that meets the depth,
                                                                    thickness, and organic-carbon requirements for a melanic
  1.   2 percent or more redox concentrations; or
                                                                    epipedon.
  2. A color value, moist, of 4 or more and 50 percent or                                                       Fulvudands, p. 86
86                                                                                                             Keys to Soil Taxonomy



DHF.      Other Udands.                                              Fulvudands
                                               Hapludands, p. 87
                                                                     Key to Subgroups
Durudands                                                            DHEA. Fulvudands that have both:

Key to Subgroups                                                        1. A lithic contact within 50 cm of the mineral soil surface
                                                                        or of the top of an organic layer with andic soil properties,
DHBA. Durudands that have, in one or more horizons above                whichever is shallower; and
the cemented horizon, aquic conditions for some time in normal
                                                                        2. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N
years (or artificial drainage) and one or more of the following:
                                                                        KCl) in the fine-earth fraction and with a total thickness of
     1.   2 percent or more redox concentrations; or                    10 cm or more at a depth between 25 cm from the mineral
                                                                        soil surface or from the top of an organic layer with andic
     2. A color value, moist, of 4 or more and 50 percent or            soil properties, whichever is shallower, and the lithic contact.
     more chroma of 2 or less either in redox depletions on faces                                           Eutric Lithic Fulvudands
     of peds or in the matrix if peds are absent; or
     3. Enough active ferrous iron to give a positive reaction       DHEB. Other Fulvudands that have a lithic contact within 50
     to alpha,alpha-dipyridyl at a time when the soil is not being   cm of the mineral soil surface or of the top of an organic layer
     irrigated.                                                      with andic soil properties, whichever is shallower.
                                                Aquic Durudands                                                    Lithic Fulvudands

                                                                     DHEC. Other Fulvudands that have, in one or more horizons
DHBB. Other Durudands that have no horizons with more
                                                                     at a depth between 50 and 100 cm either from the mineral
than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction
                                                                     soil surface or from the top of an organic layer with andic soil
and with a total thickness of 10 cm or more at a depth between
                                                                     properties, whichever is shallower, aquic conditions for some
25 and 50 cm either from the mineral soil surface or from the
                                                                     time in normal years (or artificial drainage) and one or more of
top of an organic layer with andic properties, whichever is
                                                                     the following:
shallower.
                                              Eutric Durudands          1.   2 percent or more redox concentrations; or
                                                                        2. A color value, moist, of 4 or more and 50 percent or
DHBC. Other Durudands that have a sum of extractable bases              more chroma of 2 or less either in redox depletions on faces
(by NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0         of peds or in the matrix if peds are absent; or
cmol(+)/kg in the fine-earth fraction of one or more horizons
with a total thickness of 30 cm or more at a depth between 25           3. Enough active ferrous iron to give a positive reaction
cm either from the mineral soil surface or from the top of an           to alpha,alpha-dipyridyl at a time when the soil is not being
organic layer with andic soil properties, whichever is shallower,       irrigated.
and the cemented horizon.                                                                                         Aquic Fulvudands
                                          Acrudoxic Durudands
                                                                     DHED. Other Fulvudands that are saturated with water within
                                                                     100 cm of the mineral soil surface in normal years for either or
DHBD. Other Durudands that have, on undried samples, a
                                                                     both:
1500 kPa water retention of 70 percent or more throughout a
layer 35 cm or more thick above the cemented horizon.                   1.   20 or more consecutive days; or
                                           Hydric Durudands             2.   30 or more cumulative days.
                                                                                                               Oxyaquic Fulvudands
DHBE. Other Durudands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout        DHEE. Other Fulvudands that have, on undried samples, a
a layer 50 cm or more thick within 60 cm of the mineral              1500 kPa water retention of 70 percent or more throughout
soil surface or of the top of an organic layer with andic soil       a layer 35 cm or more thick within 100 cm of the mineral
properties, whichever is shallower.                                  soil surface or of the top of an organic layer with andic soil
                                               Pachic Durudands      properties, whichever is shallower.
                                                                                                                   Hydric Fulvudands
DHBF.       Other Durudands.
                                               Typic Durudands       DHEF. Other Fulvudands that have a sum of extractable bases
Andisols                                                                                                                             87



(by NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0      top of an organic layer with andic soil properties, whichever
cmol(+)/kg in the fine-earth fraction of one or more horizons        is shallower, a layer 10 cm or more thick with more than 3.0
with a total thickness of 30 cm or more at a depth between 25        percent organic carbon and the colors of a mollic epipedon
and 100 cm either from the mineral soil surface or from the          throughout, underlying one or more horizons with a total
top of an organic layer with andic soil properties, whichever is     thickness of 10 cm or more that have a color value, moist, 1 unit
shallower.                                                           or more higher and an organic-carbon content 1 percent or more
                                          Acrudoxic Fulvudands       (absolute) lower.
                                                                                                                 Thaptic Fulvudands
DHEG.        Other Fulvudands that have both:
                                                                     DHEL. Other Fulvudands.
   1. An argillic or kandic horizon within 125 cm of the
                                                                                                                   Typic Fulvudands
   mineral soil surface or of the top of an organic layer with
   andic soil properties, whichever is shallower; and
                                                                     Hapludands
   2. A base saturation (by sum of cations) of less than 35
                                                                                                                                          A
   percent throughout the upper 50 cm of the argillic or kandic      Key to Subgroups                                                     N
                                                                                                                                          D
   horizon.                                                          DHFA. Hapludands that have a lithic contact within 50 cm of
                                             Ultic Fulvudands        the mineral soil surface or of the top of an organic layer with
                                                                     andic soil properties, whichever is shallower.
DHEH. Other Fulvudands that have both:                                                                              Lithic Hapludands
   1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N
   KCl) in the fine-earth fraction and with a total thickness of     DHFB. Other Hapludands that have anthraquic conditions.
   10 cm or more at a depth between 25 and 50 cm either from                                          Anthraquic Hapludands
   the mineral soil surface or from the top of an organic layer
   with andic soil properties, whichever is shallower; and           DHFC. Other Hapludands that have both:
   2. Throughout a layer 50 cm or more thick within 60 cm of            1. A horizon 15 cm or more thick that has 20 percent or
   the mineral soil surface or of the top of an organic layer with      more (by volume) cemented soil material within 100 cm of
   andic soil properties, whichever is shallower:                       the mineral soil surface or of the top of an organic layer with
                                                                        andic soil properties, whichever is shallower; and
        a. More than 6.0 percent organic carbon, by weighted
        average; and                                                    2. In one or more horizons at a depth between 50 and 100
                                                                        cm either from the mineral soil surface or from the top of
        b.   More than 4.0 percent organic carbon in all parts.
                                                                        an organic layer with andic soil properties, whichever is
                                      Eutric Pachic Fulvudands
                                                                        shallower, aquic conditions for some time in normal years (or
                                                                        artificial drainage) and one or more of the following:
DHEI. Other Fulvudands that have no horizons with more
than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction            a.   2 percent or more redox concentrations; or
and with a total thickness of 10 cm or more at a depth between
                                                                           b. A color value, moist, of 4 or more and 50 percent or
25 and 50 cm either from the mineral soil surface or from the
                                                                           more chroma of 2 or less either in redox depletions on
top of an organic layer with andic soil properties, whichever is
                                                                           faces of peds or in the matrix if peds are absent; or
shallower.
                                             Eutric Fulvudands             c. Enough active ferrous iron to give a positive reaction
                                                                           to alpha,alpha-dipyridyl at a time when the soil is not
DHEJ. Other Fulvudands that have, throughout a layer 50 cm                 being irrigated.
or more thick within 60 cm of the mineral soil surface or of the                                            Aquic Duric Hapludands
top of an organic layer with andic soil properties, whichever is
shallower:                                                           DHFD. Other Hapludands that have a horizon 15 cm or more
                                                                     thick that has 20 percent or more (by volume) cemented soil
   1. More than 6.0 percent organic carbon, by weighted
                                                                     material within 100 cm of the mineral soil surface or of the
   average; and
                                                                     top of an organic layer with andic soil properties, whichever is
   2.    More than 4.0 percent organic carbon in all parts.          shallower.
                                            Pachic Fulvudands                                                      Duric Hapludands

DHEK. Other Fulvudands that have, at a depth between 40              DHFE. Other Hapludands that have, in one or more horizons
and 100 cm either from the mineral soil surface or from the          at a depth between 50 and 100 cm either from the mineral
88                                                                                                                Keys to Soil Taxonomy



soil surface or from the top of an organic layer with andic soil          2. A layer 10 cm or more thick with more than 3.0
properties, whichever is shallower, aquic conditions for some             percent organic carbon and the colors of a mollic epipedon
time in normal years (or artificial drainage) and one or more of          throughout, underlying one or more horizons with a total
the following:                                                            thickness of 10 cm or more that have a color value, moist, 1
                                                                          unit or more higher and an organic-carbon content 1 percent
     1.   2 percent or more redox concentrations; or
                                                                          or more (absolute) lower.
     2. A color value, moist, of 4 or more and 50 percent or                                         Acrudoxic Thaptic Hapludands
     more chroma of 2 or less either in redox depletions on faces
     of peds or in the matrix if peds are absent; or                   DHFJ. Other Hapludands that have both:
     3. Enough active ferrous iron to give a positive reaction            1. A sum of extractable bases (by NH4OAc) plus 1N KCl-
     to alpha,alpha-dipyridyl at a time when the soil is not being        extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-
     irrigated.                                                           earth fraction of one or more horizons with a total thickness
                                               Aquic Hapludands           of 30 cm or more at a depth between 25 and 100 cm either
                                                                          from the mineral soil surface or from the top of an organic
DHFF. Other Hapludands that are saturated with water within               layer with andic soil properties, whichever is shallower; and
100 cm of the mineral soil surface in normal years for either or
                                                                          2. An argillic or kandic horizon that has both:
both:
                                                                             a. An upper boundary within 125 cm of the mineral soil
     1.   20 or more consecutive days; or
                                                                             surface or of the top of an organic layer with andic soil
     2.   30 or more cumulative days.                                        properties, whichever is shallower; and
                                            Oxyaquic Hapludands
                                                                             b. A base saturation (by sum of cations) of less than 35
                                                                             percent throughout its upper 50 cm.
DHFG. Other Hapludands that have more than 2.0
                                                                                                         Acrudoxic Ultic Hapludands
cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one
or more horizons with a total thickness of 10 cm or more at a
                                                                       DHFK. Other Hapludands that have a sum of extractable bases
depth between 25 and 50 cm either from the mineral soil surface
                                                                       (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0
or from the top of an organic layer with andic soil properties,
                                                                       cmol(+)/kg in the fine-earth fraction of one or more horizons
whichever is shallower.
                                                                       with a total thickness of 30 cm or more at a depth between 25
                                               Alic Hapludands
                                                                       and 100 cm either from the mineral soil surface or from the
                                                                       top of an organic layer with andic soil properties, whichever is
DHFH.       Other Hapludands that have both:
                                                                       shallower.
     1. A sum of extractable bases (by NH4OAc) plus 1N KCl-                                                     Acrudoxic Hapludands
     extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-
     earth fraction of one or more horizons with a total thickness     DHFL. Other Hapludands that have a 1500 kPa water
     of 30 cm or more at a depth between 25 and 100 cm either          retention of less than 15 percent on air-dried samples and less
     from the mineral soil surface or from the top of an organic       than 30 percent on undried samples throughout one or more
     layer with andic soil properties, whichever is shallower; and     layers that have andic soil properties and have a total thickness
                                                                       of 25 cm or more within 100 cm of the mineral soil surface
     2. On undried samples, a 1500 kPa water retention of 70
                                                                       or of the top of an organic layer with andic soil properties,
     percent or more throughout a layer 35 cm or more thick
                                                                       whichever is shallower.
     within 100 cm of the mineral soil surface or of the top of
                                                                                                                      Vitric Hapludands
     an organic layer with andic soil properties, whichever is
     shallower.
                                                                       DHFM. Other Hapludands that have both:
                                  Acrudoxic Hydric Hapludands
                                                                          1. On undried samples, a 1500 kPa water retention of 70
DHFI. Other Hapludands that have, at a depth between 25                   percent or more throughout a layer 35 cm or more thick
and 100 cm either from the mineral soil surface or from the               within 100 cm of the mineral soil surface or of the top of
top of an organic layer with andic soil properties, whichever is          an organic layer with andic soil properties, whichever is
shallower, both:                                                          shallower; and
     1. A sum of extractable bases (by NH4OAc) plus 1N KCl-               2. At a depth between 25 and 100 cm either from the
     extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-      mineral soil surface or from the top of an organic layer with
     earth fraction of one or more horizons with a total thickness        andic soil properties, whichever is shallower, a layer 10 cm
     of 30 cm or more; and                                                or more thick with more than 3.0 percent organic carbon and
Andisols                                                                                                                             89



   the colors of a mollic epipedon throughout, underlying one       DHFS. Other Hapludands that have both:
   or more horizons with a total thickness of 10 cm or more
                                                                       1. An argillic or kandic horizon within 125 cm of the
   that have a color value, moist, 1 unit or more higher and an
                                                                       mineral soil surface or of the top of an organic layer with
   organic-carbon content 1 percent or more (absolute) lower.
                                                                       andic soil properties, whichever is shallower; and
                                    Hydric Thaptic Hapludands
                                                                       2. A base saturation (by sum of cations) of less than 35
DHFN. Other Hapludands that have, on undried samples,                  percent throughout the upper 50 cm of the argillic or kandic
a 1500 kPa water retention of 70 percent or more throughout            horizon.
a layer 35 cm or more thick within 100 cm of the mineral                                                         Ultic Hapludands
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.                                 DHFT. Other Hapludands that have an argillic or kandic
                                              Hydric Hapludands     horizon within 125 cm of the mineral soil surface or of the
                                                                    top of an organic layer with andic soil properties, whichever is
DHFO.      Other Hapludands that have both:                         shallower.
                                                                                                                                          A
                                                                                                                   Alfic Hapludands       N
   1. A sum of extractable bases (by NH4OAc) of more than                                                                                 D
   25.0 cmol(+)/kg in the fine-earth fraction throughout one
                                                                    DHFU. Other Hapludands.
   or more horizons with a total thickness of 15 cm or more at
                                                                                                                  Typic Hapludands
   a depth between 25 and 75 cm either from the mineral soil
   surface or from the top of an organic layer with andic soil
   properties, whichever is shallower; and                          Hydrudands
   2. At a depth between 25 and 100 cm either from the              Key to Subgroups
   mineral soil surface or from the top of an organic layer with    DHDA. Hydrudands that have a lithic contact within 50 cm
   andic soil properties, whichever is shallower, a layer 10 cm     of the mineral soil surface or of the top of an organic layer with
   or more thick with more than 3.0 percent organic carbon and      andic soil properties, whichever is shallower.
   the colors of a mollic epipedon throughout, underlying one                                                     Lithic Hydrudands
   or more horizons with a total thickness of 10 cm or more
   that have a color value, moist, 1 unit or more higher and an     DHDB. Other Hydrudands that have, in one or more horizons
   organic-carbon content 1 percent or more (absolute) lower.       at a depth between 50 and 100 cm either from the mineral
                                     Eutric Thaptic Hapludands      soil surface or from the top of an organic layer with andic soil
                                                                    properties, whichever is shallower, aquic conditions for some
DHFP. Other Hapludands that have, at a depth between 25             time in normal years (or artificial drainage) and one or more of
and 100 cm either from the mineral soil surface or from the         the following:
top of an organic layer with andic soil properties, whichever
is shallower, a layer 10 cm or more thick with more than 3.0           1.   2 percent or more redox concentrations; or
percent organic carbon and the colors of a mollic epipedon             2. A color value, moist, of 4 or more and 50 percent or
throughout, underlying one or more horizons with a total               more chroma of 2 or less either in redox depletions on faces
thickness of 10 cm or more that have a color value, moist, 1 unit      of peds or in the matrix if peds are absent; or
or more higher and an organic-carbon content 1 percent or more
(absolute) lower.                                                      3. Enough active ferrous iron to give a positive reaction
                                            Thaptic Hapludands         to alpha,alpha-dipyridyl at a time when the soil is not being
                                                                       irrigated.
DHFQ. Other Hapludands that have a sum of extractable bases                                                     Aquic Hydrudands
(by NH4OAc) of more than 25.0 cmol(+)/kg in the fine-earth
fraction throughout one or more horizons with a total thickness     DHDC. Other Hydrudands that have, at a depth between 25
of 15 cm or more at a depth between 25 and 75 cm either from        and 100 cm either from the mineral soil surface or from the
the mineral soil surface or from the top of an organic layer with   top of an organic layer with andic soil properties, whichever is
andic soil properties, whichever is shallower.                      shallower, both:
                                             Eutric Hapludands         1. A sum of extractable bases (by NH4OAc) plus 1N KCl-
                                                                       extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-
DHFR. Other Hapludands that have an oxic horizon within                earth fraction of one or more horizons with a total thickness
125 cm of the mineral soil surface or of the top of an organic         of 30 cm or more; and
layer with andic soil properties, whichever is shallower.
                                                Oxic Hapludands        2. A layer 10 cm or more thick with more than 3.0
90                                                                                                              Keys to Soil Taxonomy



     percent organic carbon and the colors of a mollic epipedon      DHCB. Other Melanudands that have anthraquic conditions.
     throughout, underlying one or more horizons with a total                                       Anthraquic Melanudands
     thickness of 10 cm or more that have a color value, moist, 1
     unit or more higher and an organic-carbon content 1 percent     DHCC. Other Melanudands that have, in one or more
     or more (absolute) lower.                                       horizons at a depth between 50 and 100 cm either from the
                                Acrudoxic Thaptic Hydrudands         mineral soil surface or from the top of an organic layer with
                                                                     andic soil properties, whichever is shallower, aquic conditions
DHDD. Other Hydrudands that have a sum of extractable                for some time in normal years (or artificial drainage) and one or
bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less         more of the following:
than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
                                                                        1.   2 percent or more redox concentrations; or
horizons with a total thickness of 30 cm or more at a depth
between 25 and 100 cm either from the mineral soil surface              2. A color value, moist, of 4 or more and 50 percent or
or from the top of an organic layer with andic soil properties,         more chroma of 2 or less either in redox depletions on faces
whichever is shallower.                                                 of peds or in the matrix if peds are absent; or
                                        Acrudoxic Hydrudands
                                                                        3. Enough active ferrous iron to give a positive reaction
DHDE. Other Hydrudands that have, at a depth between 25                 to alpha,alpha-dipyridyl at a time when the soil is not being
and 100 cm either from the mineral soil surface or from the             irrigated.
top of an organic layer with andic soil properties, whichever                                                   Aquic Melanudands
is shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon           DHCD. Other Melanudands that have both:
throughout, underlying one or more horizons with a total                1. A sum of extractable bases (by NH4OAc) plus 1N KCl-
thickness of 10 cm or more that have a color value, moist, 1 unit       extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-
or more higher and an organic-carbon content 1 percent or more          earth fraction of one or more horizons with a total thickness
(absolute) lower.                                                       of 30 cm or more at a depth between 25 and 100 cm either
                                           Thaptic Hydrudands           from the mineral soil surface or from the top of an organic
                                                                        layer with andic soil properties, whichever is shallower; and
DHDF. Other Hydrudands that have a sum of extractable bases
(by NH4OAc) of more than 25.0 cmol(+)/kg in the fine-earth              2. A 1500 kPa water retention of less than 15 percent
fraction throughout one or more horizons with a total thickness         on air-dried samples and less than 30 percent on undried
of 15 cm or more at a depth between 25 and 75 cm either from            samples throughout one or more layers that have andic soil
the mineral soil surface or from the top of an organic layer with       properties and have a total thickness of 25 cm or more within
andic soil properties, whichever is shallower.                          100 cm of the mineral soil surface or of the top of an organic
                                             Eutric Hydrudands          layer with andic soil properties, whichever is shallower.
                                                                                                      Acrudoxic Vitric Melanudands
DHDG.       Other Hydrudands that have both:
                                                                     DHCE. Other Melanudands that have both:
     1. An argillic or kandic horizon within 125 cm of the
     mineral soil surface or of the top of an organic layer with        1. A sum of extractable bases (by NH4OAc) plus 1N KCl-
     andic soil properties, whichever is shallower; and                 extractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-
                                                                        earth fraction of one or more horizons with a total thickness
     2. A base saturation (by sum of cations) of less than 35
                                                                        of 30 cm or more at a depth between 25 and 100 cm either
     percent throughout the upper 50 cm of the argillic or kandic
                                                                        from the mineral soil surface or from the top of an organic
     horizon.
                                                                        layer with andic soil properties, whichever is shallower; and
                                              Ultic Hydrudands
                                                                        2. On undried samples, a 1500 kPa water retention of 70
DHDH.       Other Hydrudands.                                           percent or more throughout a layer 35 cm or more thick
                                               Typic Hydrudands         within 100 cm of the mineral soil surface or of the top of
                                                                        an organic layer with andic soil properties, whichever is
Melanudands                                                             shallower.
                                                                                                   Acrudoxic Hydric Melanudands
Key to Subgroups
DHCA. Melanudands that have a lithic contact within 50 cm            DHCF. Other Melanudands that have a sum of extractable
of the mineral soil surface or of the top of an organic layer that   bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less
has andic soil properties, whichever is shallower.                   than 2.0 cmol(+)/kg in the fine-earth fraction of one or more
                                             Lithic Melanudands      horizons with a total thickness of 30 cm or more at a depth
Andisols                                                                                                                             91



between 25 and 100 cm either from the mineral soil surface          soil surface or of the top of an organic layer with andic soil
or from the top of an organic layer with andic soil properties,     properties, whichever is shallower.
whichever is shallower.                                                                                         Hydric Melanudands
                                       Acrudoxic Melanudands
                                                                    DHCL. Other Melanudands that have, at a depth between 40
DHCG. Other Melanudands that have both:                             and 100 cm either from the mineral soil surface or from the
                                                                    top of an organic layer with andic soil properties, whichever
   1. More than 6.0 percent organic carbon and the colors of
                                                                    is shallower, a layer 10 cm or more thick with more than 3.0
   a mollic epipedon throughout a layer 50 cm or more thick
                                                                    percent organic carbon and the colors of a mollic epipedon
   within 60 cm of the mineral soil surface or of the top of
                                                                    throughout, underlying one or more horizons with a total
   an organic layer with andic soil properties, whichever is
                                                                    thickness of 10 cm or more that have a color value, moist, 1 unit
   shallower; and
                                                                    or more higher and an organic-carbon content 1 percent or more
   2. A 1500 kPa water retention of less than 15 percent            (absolute) lower.
   on air-dried samples and less than 30 percent on undried                                                   Thaptic Melanudands
                                                                                                                                          A
   samples throughout one or more layers that have andic soil                                                                             N
                                                                                                                                          D
   properties and have a total thickness of 25 cm or more within    DHCM. Other Melanudands that have both:
   100 cm of the mineral soil surface or of the top of an organic
                                                                       1. An argillic or kandic horizon within 125 cm of the
   layer with andic soil properties, whichever is shallower.
                                                                       mineral soil surface or of the top of an organic layer with
                                     Pachic Vitric Melanudands
                                                                       andic soil properties, whichever is shallower; and
DHCH. Other Melanudands that have a 1500 kPa water                     2. A base saturation (by sum of cations) of less than 35
retention of less than 15 percent on air-dried samples and less        percent throughout the upper 50 cm of the argillic or kandic
than 30 percent on undried samples throughout one or more              horizon.
layers that have andic soil properties and have a total thickness                                              Ultic Melanudands
of 25 cm or more within 100 cm of the mineral soil surface
or of the top of an organic layer with andic soil properties,       DHCN. Other Melanudands that have a sum of extractable
whichever is shallower.                                             bases (by NH4OAc) of more than 25.0 cmol(+)/kg in the
                                             Vitric Melanudands     fine-earth fraction throughout one or more horizons with a
                                                                    total thickness of 15 cm or more at a depth between 25 and 75
DHCI.      Other Melanudands that have both:                        cm either from the mineral soil surface or from the top of an
                                                                    organic layer with andic soil properties, whichever is shallower.
   1. On undried samples, a 1500 kPa water retention of 70                                                     Eutric Melanudands
   percent or more throughout a layer 35 cm or more thick
   within 100 cm of the mineral soil surface or of the top of       DHCO. Other Melanudands.
   an organic layer with andic soil properties, whichever is                                                    Typic Melanudands
   shallower; and
   2. More than 6.0 percent organic carbon and the colors of        Placudands
   a mollic epipedon throughout a layer 50 cm or more thick
                                                                    Key to Subgroups
   within 60 cm of the mineral soil surface or of the top of
   an organic layer with andic soil properties, whichever is        DHAA. Placudands that have a lithic contact within 50 cm of
   shallower.                                                       the mineral soil surface or of the top of an organic layer that has
                                   Hydric Pachic Melanudands        andic soil properties, whichever is shallower.
                                                                                                                   Lithic Placudands
DHCJ. Other Melanudands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout       DHAB. Other Placudands that have, in one or more horizons
a layer 50 cm or more thick within 60 cm of the mineral             at a depth between 50 cm either from the mineral soil surface
soil surface or of the top of an organic layer with andic soil      or from the top of an organic layer with andic soil properties,
properties, whichever is shallower.                                 whichever is shallower, and the placic horizon, aquic conditions
                                            Pachic Melanudands      for some time in normal years (or artificial drainage) and one or
                                                                    more of the following:
DHCK. Other Melanudands that have, on undried samples,
                                                                       1.   2 percent or more redox concentrations; or
a 1500 kPa water retention of 70 percent or more throughout
a layer 35 cm or more thick within 100 cm of the mineral               2. A color value, moist, of 4 or more and 50 percent or
92                                                                                                             Keys to Soil Taxonomy



     more chroma of 2 or less either in redox depletions on faces       to alpha,alpha-dipyridyl at a time when the soil is not being
     of peds or in the matrix if peds are absent; or                    irrigated.
                                                                                                                  Aquic Durustands
     3. Enough active ferrous iron to give a positive reaction
     to alpha,alpha-dipyridyl at a time when the soil is not being
                                                                     DGAB. Other Durustands that have, at a depth between 25
     irrigated.
                                                                     and 100 cm either from the mineral soil surface or from the
                                               Aquic Placudands
                                                                     top of an organic layer with andic soil properties, whichever
                                                                     is shallower, a layer 10 cm or more thick with more than 3.0
DHAC. Other Placudands that have a sum of extractable bases
                                                                     percent organic carbon and the colors of a mollic epipedon
(by NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0
                                                                     throughout, underlying one or more horizons with a total
cmol(+)/kg in the fine-earth fraction of one or more horizons
                                                                     thickness of 10 cm or more that have a color value, moist, 1 unit
with a total thickness of 30 cm or more at a depth between 25
                                                                     or more higher and an organic-carbon content 1 percent or more
cm either from the mineral soil surface or from the top of an
                                                                     (absolute) lower.
organic layer with andic soil properties, whichever is shallower,
                                                                                                                 Thaptic Durustands
and the placic horizon.
                                          Acrudoxic Placudands
                                                                     DGAC. Other Durustands that have a melanic, mollic, or
                                                                     umbric epipedon.
DHAD. Other Placudands that have, on undried samples, a
                                                                                                            Humic Durustands
1500 kPa water retention of 70 percent or more throughout
a layer 35 cm or more thick within 100 cm of the mineral
                                                                     DGAD. Other Durustands.
soil surface or of the top of an organic layer with andic soil
                                                                                                                   Typic Durustands
properties, whichever is shallower.
                                               Hydric Placudands
                                                                     Haplustands
DHAE. Other Placudands.                                              Key to Subgroups
                                                Typic Placudands
                                                                     DGBA. Haplustands that have a lithic contact within 50 cm
                                                                     of the mineral soil surface or of the top of an organic layer with
Ustands                                                              andic soil properties, whichever is shallower.
Key to Great Groups                                                                                                Lithic Haplustands

DGA. Ustands that have, in 75 percent or more of each                DGBB. Other Haplustands that have, in one or more horizons
pedon, a cemented horizon within 100 cm of the mineral               at a depth between 50 and 100 cm either from the mineral
soil surface or of the top of an organic layer with andic soil       soil surface or from the top of an organic layer with andic soil
properties, whichever is shallower.                                  properties, whichever is shallower, aquic conditions for some
                                               Durustands, p. 92     time in normal years (or artificial drainage) and one or more of
                                                                     the following:
DGB.      Other Ustands.
                                                Haplustands, p. 92      1.   2 percent or more redox concentrations; or
                                                                        2. A color value, moist, of 4 or more and 50 percent or
Durustands                                                              more chroma of 2 or less either in redox depletions on faces
Key to Subgroups                                                        of peds or in the matrix if peds are absent; or

DGAA. Durustands that have, in one or more horizons at                  3. Enough active ferrous iron to give a positive reaction
a depth between 50 and 100 cm either from the mineral soil              to alpha,alpha-dipyridyl at a time when the soil is not being
surface or from the top of an organic layer with andic soil             irrigated.
properties, whichever is shallower, aquic conditions for some                                                    Aquic Haplustands
time in normal years (or artificial drainage) and one or more of
the following:                                                       DGBC. Other Haplustands that have both:
     1.   2 percent or more redox concentrations; or                    1. A sum of extractable bases (by NH4OAc) plus 1N KCl-
                                                                        extractable Al3+ totaling less than 15.0 cmol(+)/kg in the
     2. A color value, moist, of 4 or more and 50 percent or
                                                                        fine-earth fraction throughout one or more horizons with a
     more chroma of 2 or less either in redox depletions on faces
                                                                        total thickness of 60 cm or more within 75 cm of the mineral
     of peds or in the matrix if peds are absent; or
                                                                        soil surface or of the top of an organic layer with andic soil
     3.   Enough active ferrous iron to give a positive reaction        properties, whichever is shallower; and
Andisols                                                                                                                             93



   2. A 1500 kPa water retention of less than 15 percent               1. An argillic or kandic horizon within 125 cm of the
   on air-dried samples and less than 30 percent on undried            mineral soil surface or of the top of an organic layer with
   samples throughout one or more layers that have andic soil          andic soil properties, whichever is shallower; and
   properties and have a total thickness of 25 cm or more within
                                                                       2. A base saturation (by sum of cations) of less than 35
   100 cm of the mineral soil surface or of the top of an organic
                                                                       percent throughout the upper 50 cm or throughout the entire
   layer with andic soil properties, whichever is shallower.
                                                                       argillic or kandic horizon if it is less than 50 cm thick.
                                     Dystric Vitric Haplustands
                                                                                                                     Ultic Haplustands
DGBD. Other Haplustands that have a 1500 kPa water                  DGBK. Other Haplustands that have an argillic or kandic
retention of less than 15 percent on air-dried samples and less     horizon within 125 cm of the mineral soil surface or of the
than 30 percent on undried samples throughout one or more           top of an organic layer with andic soil properties, whichever is
layers that have andic soil properties and have a total thickness   shallower.
of 25 cm or more within 100 cm of the mineral soil surface                                                         Alfic Haplustands
or of the top of an organic layer with andic soil properties,                                                                             A
whichever is shallower.                                                                                                                   N
                                                                    DGBL. Other Haplustands that have a melanic, mollic, or               D
                                              Vitric Haplustands    umbric epipedon.
                                                                                                          Humic Haplustands
DGBE. Other Haplustands that have more than 6.0 percent
organic carbon and the colors of a mollic epipedon throughout       DGBM. Other Haplustands.
a layer 50 cm or more thick within 60 cm of the mineral                                                          Typic Haplustands
soil surface or of the top of an organic layer with andic soil
properties, whichever is shallower.
                                              Pachic Haplustands    Vitrands
                                                                    Key to Great Groups
DGBF. Other Haplustands that have, at a depth between 25
and 100 cm either from the mineral soil surface or from the         DFA. Vitrands that have an ustic soil moisture regime.
top of an organic layer with andic soil properties, whichever                                                  Ustivitrands, p. 94
is shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon          DFB. Other Vitrands.
throughout, underlying one or more horizons with a total                                                           Udivitrands, p. 93
thickness of 10 cm or more that have a color value, moist, 1 unit
or more higher and an organic-carbon content 1 percent or more      Udivitrands
(absolute) lower.                                                   Key to Subgroups
                                           Thaptic Haplustands
                                                                    DFBA. Udivitrands that have a lithic contact within 50 cm of
DGBG. Other Haplustands that have a calcic horizon within           the mineral soil surface or of the top of an organic layer with
125 cm of the mineral soil surface or of the top of an organic      andic soil properties, whichever is shallower.
layer with andic soil properties, whichever is shallower.                                                          Lithic Udivitrands
                                             Calcic Haplustands
                                                                    DFBB. Other Udivitrands that have, in one or more horizons
DGBH. Other Haplustands that have a sum of extractable              at a depth between 50 and 100 cm either from the mineral
bases (by NH4OAc) plus 1N KCl-extractable Al3+ totaling less        soil surface or from the top of an organic layer with andic soil
than 15.0 cmol(+)/kg in the fine-earth fraction throughout one      properties, whichever is shallower, aquic conditions for some
or more horizons with a total thickness of 60 cm or more within     time in normal years (or artificial drainage) and one or more of
75 cm either of the mineral soil surface or of the top of an        the following:
organic layer with andic soil properties, whichever is shallower.      1.   2 percent or more redox concentrations; or
                                            Dystric Haplustands
                                                                       2. A color value, moist, of 4 or more and 50 percent or
                                                                       more chroma of 2 or less either in redox depletions on faces
DGBI. Other Haplustands that have an oxic horizon within
                                                                       of peds or in the matrix if peds are absent; or
125 cm of the mineral soil surface or of the top of an organic
layer with andic soil properties, whichever is shallower.              3. Enough active ferrous iron to give a positive reaction
                                               Oxic Haplustands        to alpha,alpha-dipyridyl at a time when the soil is not being
                                                                       irrigated.
DGBJ.      Other Haplustands that have both:                                                                     Aquic Udivitrands
94                                                                                                               Keys to Soil Taxonomy



DFBC. Other Udivitrands that are saturated with water within         time in normal years (or artificial drainage) and one or more of
100 cm of the mineral soil surface in normal years for either or     the following:
both:
                                                                        1.   2 percent or more redox concentrations; or
     1.   20 or more consecutive days; or
                                                                        2. A color value, moist, of 4 or more and 50 percent or
     2.   30 or more cumulative days.                                   more chroma of 2 or less either in redox depletions on faces
                                            Oxyaquic Udivitrands        of peds or in the matrix if peds are absent; or
                                                                        3. Enough active ferrous iron to give a positive reaction
DFBD. Other Udivitrands that have, at a depth between 25
                                                                        to alpha,alpha-dipyridyl at a time when the soil is not being
and 100 cm either from the mineral soil surface or from the
                                                                        irrigated.
top of an organic layer with andic soil properties, whichever
                                                                                                                  Aquic Ustivitrands
is shallower, a layer 10 cm or more thick with more than 3.0
percent organic carbon and the colors of a mollic epipedon
                                                                     DFAC. Other Ustivitrands that have, at a depth between 25
throughout, underlying one or more horizons with a total
                                                                     and 100 cm either from the mineral soil surface or from the
thickness of 10 cm or more that have a color value, moist, 1 unit
                                                                     top of an organic layer with andic soil properties, whichever
or more higher and an organic-carbon content 1 percent or more
                                                                     is shallower, a layer 10 cm or more thick with more than 3.0
(absolute) lower.
                                                                     percent organic carbon and the colors of a mollic epipedon
                                            Thaptic Udivitrands
                                                                     throughout, underlying one or more horizons with a total
                                                                     thickness of 10 cm or more that have a color value, moist, 1 unit
DFBE.       Other Udivitrands that have both:
                                                                     or more higher and an organic-carbon content 1 percent or more
     1. An argillic or kandic horizon within 125 cm of the           (absolute) lower.
     mineral soil surface or of the top of an organic layer with                                                 Thaptic Ustivitrands
     andic soil properties, whichever is shallower; and
                                                                     DFAD. Other Ustivitrands that have a calcic horizon within
     2. A base saturation (by sum of cations) of less than 35
                                                                     125 cm of the soil surface or of the top of an organic layer with
     percent throughout the upper 50 cm of the argillic or kandic
                                                                     andic soil properties, whichever is shallower.
     horizon.
                                                                                                                   Calcic Ustivitrands
                                               Ultic Udivitrands
                                                                     DFAE. Other Ustivitrands that have a melanic, mollic, or
DFBF. Other Udivitrands that have an argillic or kandic
                                                                     umbric epipedon.
horizon within 125 cm of the mineral soil surface or of the
                                                                                                             Humic Ustivitrands
top of an organic layer with andic soil properties, whichever is
shallower.
                                                                     DFAF. Other Ustivitrands.
                                                Alfic Udivitrands
                                                                                                                     Typic Ustivitrands
DFBG. Other Udivitrands that have a melanic, mollic, or
umbric epipedon.                                                     Xerands
                                       Humic Udivitrands
                                                                     Key to Great Groups
DFBH. Other Udivitrands.                                             DEA. Xerands that have a 1500 kPa water retention of less
                                                Typic Udivitrands    than 15 percent on air-dried samples and less than 30 percent on
                                                                     undried samples throughout 60 percent or more of the thickness
Ustivitrands                                                         either:
Key to Subgroups                                                        1. Within 60 cm of the mineral soil surface or of the top
                                                                        of an organic layer with andic soil properties, whichever is
DFAA. Ustivitrands that have a lithic contact within 50 cm of
                                                                        shallower, if there is no densic, lithic, or paralithic contact,
the mineral soil surface or of the top of an organic layer with
                                                                        duripan, or petrocalcic horizon within that depth; or
andic soil properties, whichever is shallower.
                                               Lithic Ustivitrands      2. Between the mineral soil surface or the top of an organic
                                                                        layer with andic soil properties, whichever is shallower, and a
DFAB. Other Ustivitrands that have, in one or more horizons             densic, lithic, or paralithic contact, a duripan, or a petrocalcic
at a depth between 50 and 100 cm either from the mineral                horizon.
soil surface or from the top of an organic layer with andic soil                                                      Vitrixerands, p. 95
properties, whichever is shallower, aquic conditions for some
Andisols                                                                                                                            95



DEB.    Other Xerands that have a melanic epipedon.                  DECF. Other Haploxerands that have both:
                                        Melanoxerands, p. 95
                                                                        1. A mollic or umbric epipedon; and
DEC.    Other Xerands.                                                  2. An argillic or kandic horizon within 125 cm of the
                                            Haploxerands, p. 95         mineral soil surface or of the top of an organic layer with
                                                                        andic soil properties, whichever is shallower.
Haploxerands                                                                                               Alfic Humic Haploxerands
Key to Subgroups
                                                                     DECG. Other Haploxerands that have an argillic or kandic
DECA. Haploxerands that have a lithic contact within 50 cm           horizon within 125 cm of the mineral soil surface or of the
of the mineral soil surface or of the top of an organic layer with   top of an organic layer with andic soil properties, whichever is
andic soil properties, whichever is shallower.                       shallower.
                                             Lithic Haploxerands                                                  Alfic Haploxerands
                                                                                                                                          A
DECB. Other Haploxerands that have, in one or more horizons          DECH. Other Haploxerands that have a mollic or umbric                N
                                                                                                                                          D
at a depth between 50 and 100 cm either from the mineral             epipedon.
soil surface or from the top of an organic layer with andic soil                                         Humic Haploxerands
properties, whichever is shallower, aquic conditions for some
time in normal years (or artificial drainage) and one or more of     DECI. Other Haploxerands.
the following:                                                                                                  Typic Haploxerands
   1.   2 percent or more redox concentrations; or
                                                                     Melanoxerands
   2. A color value, moist, of 4 or more and 50 percent or
   more chroma of 2 or less either in redox depletions on faces      Key to Subgroups
   of peds or in the matrix if peds are absent; or                   DEBA. Melanoxerands that have more than 6.0 percent
   3. Enough active ferrous iron to give a positive reaction         organic carbon and the colors of a mollic epipedon throughout
   to alpha,alpha-dipyridyl at a time when the soil is not being     a layer 50 cm or more thick within 60 cm of the mineral
   irrigated.                                                        soil surface or of the top of an organic layer with andic soil
                                          Aquic Haploxerands         properties, whichever is shallower.
                                                                                                                Pachic Melanoxerands
DECC. Other Haploxerands that have, at a depth between 25
and 100 cm from the mineral soil surface or from the top of an       DEBB. Other Melanoxerands.
organic layer with andic soil properties, whichever is shallower,                                              Typic Melanoxerands
a layer 10 cm or more thick with more than 3.0 percent
organic carbon and the colors of a mollic epipedon throughout,       Vitrixerands
underlying one or more horizons with a total thickness of 10 cm      Key to Subgroups
or more that have a color value, moist, 1 unit or more higher and
an organic-carbon content 1 percent or more (absolute) lower.        DEAA. Vitrixerands that have a lithic contact within 50 cm
                                          Thaptic Haploxerands       of the mineral soil surface or of the top of an organic layer with
                                                                     andic soil properties, whichever is shallower.
DECD. Other Haploxerands that have a calcic horizon within                                                         Lithic Vitrixerands
125 cm of the mineral soil surface.
                                     Calcic Haploxerands             DEAB. Other Vitrixerands that have, in one or more horizons
                                                                     at a depth between 50 and 100 cm either from the mineral
DECE.      Other Haploxerands that have both:                        soil surface or from the top of an organic layer with andic soil
                                                                     properties, whichever is shallower, aquic conditions for some
   1. An argillic or kandic horizon within 125 cm of the             time in normal years (or artificial drainage) and one or more of
   mineral soil surface or of the top of an organic layer with       the following:
   andic soil properties, whichever is shallower; and
                                                                        1.   2 percent or more redox concentrations; or
   2. A base saturation (by sum of cations) of less than 35
   percent throughout the upper 50 cm of the argillic or kandic         2. A color value, moist, of 4 or more and 50 percent or
   horizon.                                                             more chroma of 2 or less either in redox depletions on faces
                                           Ultic Haploxerands           of peds or in the matrix if peds are absent; or
96



     3. Enough active ferrous iron to give a positive reaction       DEAE. Other Vitrixerands that have both:
     to alpha,alpha-dipyridyl at a time when the soil is not being
                                                                        1. An argillic or kandic horizon within 125 cm of the
     irrigated.
                                                                        mineral soil surface or of the top of an organic layer with
                                              Aquic Vitrixerands
                                                                        andic soil properties, whichever is shallower; and
DEAC. Other Vitrixerands that have, at a depth between 25               2. A base saturation (by sum of cations) of less than 35
and 100 cm from the mineral soil surface or from the top of an          percent throughout the upper 50 cm or throughout the entire
organic layer with andic soil properties, whichever is shallower,       argillic or kandic horizon if it is less than 50 cm thick.
a layer 10 cm or more thick with more than 3.0 percent                                                                 Ultic Vitrixerands
organic carbon and the colors of a mollic epipedon throughout,
underlying one or more horizons with a total thickness of 10 cm      DEAF. Other Vitrixerands that have an argillic or kandic
or more that have a color value, moist, 1 unit or more higher and    horizon within 125 cm of the mineral soil surface or of the
an organic-carbon content 1 percent or more (absolute) lower.        top of an organic layer with andic soil properties, whichever is
                                           Thaptic Vitrixerands      shallower.
                                                                                                                    Alfic Vitrixerands
DEAD. Other Vitrixerands that have both:
                                                                     DEAG. Other Vitrixerands that have a melanic, mollic, or
     1. A melanic, mollic, or umbric epipedon; and
                                                                     umbric epipedon.
     2. An argillic or kandic horizon within 125 cm of the                                                  Humic Vitrixerands
     mineral soil surface or of the top of an organic layer with
     andic soil properties, whichever is shallower.                  DEAH. Other Vitrixerands.
                                         Alfic Humic Vitrixerands                                                  Typic Vitrixerands
                                                                                                                                  97




CHAPTER 7

                                                                                                                    Aridisols

Key to Suborders                                                     1. A clay increase of 15 percent or more (absolute) within
                                                                     a vertical distance of 2.5 cm either within the argillic horizon
GA. Aridisols that have a cryic soil temperature regime.             or at its upper boundary; or
                                                Cryids, p. 112
                                                                     2. An argillic horizon that extends to 150 cm or more from
GB. Other Aridisols that have a salic horizon within 100 cm of       the soil surface, that does not have a clay decrease with
the soil surface.                                                    increasing depth of 20 percent or more (relative) from the
                                                 Salids, p. 122      maximum clay content, and that has, in 50 percent or more of
                                                                     the matrix in some part between 100 and 150 cm, either:            A
                                                                                                                                        R
                                                                                                                                        I
GC. Other Aridisols that have a duripan within 100 cm of the              a.   Hue of 7.5YR or redder and chroma of 5 or more; or
soil surface.
                                               Durids, p. 115             b. Hue of 7.5YR or redder and value, moist, of 3 or less
                                                                          and value, dry, of 4 or less.
GD. Other Aridisols that have a gypsic or petrogypsic                                                          Paleargids, p. 104
horizon within 100 cm of the soil surface and do not have a
petrocalcic horizon overlying these horizons.                      GED. Other Argids that have a gypsic horizon within 150 cm
                                                Gypsids, p. 118    of the soil surface.
                                                                                                             Gypsiargids, p. 99
GE. Other Aridisols that have an argillic or natric horizon
and do not have a petrocalcic horizon within 100 cm of the soil    GEE. Other Argids that have a calcic horizon within 150 cm
surface.                                                           of the soil surface.
                                                   Argids, p. 97                                              Calciargids, p. 97

GF. Other Aridisols that have a calcic or petrocalcic horizon      GEF.    Other Argids.
within 100 cm of the soil surface.                                                                               Haplargids, p. 100
                                                Calcids, p. 105    Calciargids
                                                                   Key to Subgroups
GG.   Other Aridisols.
                                                Cambids, p. 108    GEEA. Calciargids that have a lithic contact within 50 cm of
                                                                   the soil surface.
                                                                                                              Lithic Calciargids
Argids
                                                                   GEEB. Other Calciargids that have both:
Key to Great Groups
                                                                     1.    One or both of the following:
GEA. Argids that have a duripan or a petrocalcic or
petrogypsic horizon within 150 cm of the soil surface.                    a. Cracks within 125 cm of the soil surface that are 5
                                            Petroargids, p. 105           mm or more wide through a thickness of 30 cm or more
                                                                          for some time in normal years and slickensides or wedge-
GEB. Other Argids that have a natric horizon.                             shaped peds in a layer 15 cm or more thick that has its
                                           Natrargids, p. 102             upper boundary within 125 cm of the soil surface; or
                                                                          b. A linear extensibility of 6.0 cm or more between the
                                                                          soil surface and either a depth of 100 cm or a densic,
GEC. Other Argids that do not have a densic, lithic, or
                                                                          lithic, or paralithic contact if shallower; and
paralithic contact within 50 cm of the soil surface and have
either:                                                              2. A moisture control section that, in normal years, is dry in
98                                                                                                               Keys to Soil Taxonomy



     all parts for less than three-fourths of the time (cumulative)       is dry in all parts for less than three-fourths of the time
     when the soil temperature at a depth of 50 cm below the              (cumulative) when the soil temperature at a depth of 50 cm
     soil surface is 5 oC or higher and a soil moisture regime that       below the soil surface is 5 oC or higher and a soil moisture
     borders on xeric.                                                    regime that borders on ustic.
                                                Xerertic Calciargids                                             Arenic Ustic Calciargids

GEEC. Other Calciargids that have both:                                GEEG. Other Calciargids that meet sandy or sandy-skeletal
                                                                       particle-size class criteria throughout a layer extending from the
     1.    One or both of the following:
                                                                       soil surface to the top of an argillic horizon at a depth of 50 cm
          a. Cracks within 125 cm of the soil surface that are 5       or more.
          mm or more wide through a thickness of 30 cm or more                                                         Arenic Calciargids
          for some time in normal years and slickensides or wedge-
          shaped peds in a layer 15 cm or more thick that has its      GEEH. Other Calciargids that have both:
          upper boundary within 125 cm of the soil surface; or
                                                                          1. One or more horizons, within 100 cm of the soil surface
          b. A linear extensibility of 6.0 cm or more between the         and with a combined thickness of 15 cm or more, that
          soil surface and either a depth of 100 cm or a densic,          contain 20 percent or more (by volume) durinodes or are
          lithic, or paralithic contact if shallower; and                 brittle and have at least a firm rupture-resistance class when
                                                                          moist; and
     2. A moisture control section that, in normal years, is dry in
     all parts for less than three-fourths of the time (cumulative)       2. A moisture control section that, in normal years, is dry in
     when the soil temperature at a depth of 50 cm below the              all parts for less than three-fourths of the time (cumulative)
     soil surface is 5 oC or higher and a soil moisture regime that       when the soil temperature at a depth of 50 cm below the
     borders on ustic.                                                    soil surface is 5 oC or higher and a soil moisture regime that
                                                Ustertic Calciargids      borders on xeric.
                                                                                                            Durinodic Xeric Calciargids
GEED. Other Calciargids that have one or both of the
following:                                                             GEEI. Other Calciargids that have one or more horizons,
                                                                       within 100 cm of the soil surface and with a combined thickness
     1. Cracks within 125 cm of the soil surface that are 5 mm
                                                                       of 15 cm or more, that contain 20 percent or more (by volume)
     or more wide through a thickness of 30 cm or more for some
                                                                       durinodes or are brittle and have at least a firm rupture-
     time in normal years and slickensides or wedge-shaped peds
                                                                       resistance class when moist.
     in a layer 15 cm or more thick that has its upper boundary
                                                                                                                  Durinodic Calciargids
     within 125 cm of the soil surface; or
     2. A linear extensibility of 6.0 cm or more between the soil      GEEJ. Other Calciargids that have both:
     surface and either a depth of 100 cm or a densic, lithic, or
                                                                          1. One or more horizons, within 100 cm of the soil
     paralithic contact if shallower.
                                                                          surface and with a combined thickness of 15 cm or more,
                                                Vertic Calciargids
                                                                          that contain 20 percent or more (by volume) nodules or
                                                                          concretions; and
GEEE. Other Calciargids that are either:
                                                                          2. A moisture control section that, in normal years, is dry in
     1. Irrigated and have aquic conditions for some time in
                                                                          all parts for less than three-fourths of the time (cumulative)
     normal years in one or more layers within 100 cm of the soil
                                                                          when the soil temperature at a depth of 50 cm below the
     surface; or
                                                                          soil surface is 5 oC or higher and a soil moisture regime that
     2. Saturated with water in one or more layers within 100             borders on xeric.
     cm of the soil surface for 1 month or more in normal years.                                           Petronodic Xeric Calciargids
                                               Aquic Calciargids
                                                                       GEEK. Other Calciargids that have both:
GEEF.       Other Calciargids that:
                                                                          1. One or more horizons, within 100 cm of the soil
     1. Meet sandy or sandy-skeletal particle-size class criteria         surface and with a combined thickness of 15 cm or more,
     throughout a layer extending from the soil surface to the top        that contain 20 percent or more (by volume) nodules or
     of an argillic horizon at a depth of 50 cm or more; and              concretions; and
     2.    Have a moisture control section that, in normal years,         2. A moisture control section that, in normal years, is dry in
Aridisols                                                                                                                           99



   all parts for less than three-fourths of the time (cumulative)    parts of the moisture control section for less than three-fourths
   when the soil temperature at a depth of 50 cm below the           of the time (cumulative) when the soil temperature at a depth
   soil surface is 5 oC or higher and a soil moisture regime that    of 50 cm below the soil surface is 5 oC or higher and have a soil
   borders on ustic                                                  moisture regime that borders on ustic.
                                    Petronodic Ustic Calciargids                                                      Ustic Calciargids

GEEL. Other Calciargids that have one or more horizons,              GEEQ. Other Calciargids.
within 100 cm of the soil surface and with a combined thickness                                                    Typic Calciargids
of 15 cm or more, that contain 20 percent or more (by volume)
nodules or concretions.                                              Gypsiargids
                                        Petronodic Calciargids
                                                                     Key to Subgroups
GEEM.       Other Calciargids that have both:                        GEDA. Gypsiargids that are either:
   1. A moisture control section that, in normal years, is dry in       1. Irrigated and have aquic conditions for some time in
   all parts for less than three-fourths of the time (cumulative)       normal years in one or more layers within 100 cm of the soil
   when the soil temperature at a depth of 50 cm below the              surface; or
   soil surface is 5 oC or higher and a soil moisture regime that                                                                         A
   borders on xeric; and                                                2. Are saturated with water in one or more layers within          R
                                                                                                                                          I
                                                                        100 cm of the soil surface for 1 month or more in normal
   2. Throughout one or more horizons with a total thickness            years.
   of 18 cm or more within 75 cm of the soil surface, one or                                                      Aquic Gypsiargids
   both of the following:
      a. More than 35 percent (by volume) fragments coarser          GEDB. Other Gypsiargids that have one or more horizons,
      than 2.0 mm, of which more than 66 percent is cinders,         within 100 cm of the soil surface and with a combined thickness
      pumice, and pumicelike fragments; or                           of 15 cm or more, that either contain 20 percent or more (by
                                                                     volume) durinodes or are brittle and have at least a firm rupture-
      b. A fine-earth fraction containing 30 percent or more         resistance class when moist.
      particles 0.02 to 2.0 mm in diameter, of which 5 percent                                                Durinodic Gypsiargids
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent
      extracted by ammonium oxalate) times 60] plus the              GEDC. Other Gypsiargids that have both:
      volcanic glass (percent) is 30 or more.
                                      Vitrixerandic Calciargids         1. A moisture control section that, in normal years, is dry in
                                                                        all parts for less than three-fourths of the time (cumulative)
GEEN. Other Calciargids that have, throughout one or more               when the soil temperature at a depth of 50 cm below the
horizons with a total thickness of 18 cm or more within 75 cm           soil surface is 5 oC or higher and a soil moisture regime that
of the soil surface, one or both of the following:                      borders on xeric; and
   1. More than 35 percent (by volume) fragments coarser                2. Throughout one or more horizons with a total thickness
   than 2.0 mm, of which more than 66 percent is cinders,               of 18 cm or more within 75 cm of the soil surface, one or
   pumice, and pumicelike fragments; or                                 both of the following:
   2. A fine-earth fraction containing 30 percent or more                  a. More than 35 percent (by volume) fragments coarser
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or             than 2.0 mm, of which more than 66 percent is cinders,
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted         pumice, and pumicelike fragments; or
   by ammonium oxalate) times 60] plus the volcanic glass
   (percent) is 30 or more.                                                b. A fine-earth fraction containing 30 percent or more
                                           Vitrandic Calciargids           particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                                                           or more is volcanic glass, and [(Al plus 1/2 Fe, percent
GEEO. Other Calciargids that, in normal years, are dry in all              extracted by ammonium oxalate) times 60] plus the
parts of the moisture control section for less than three-fourths          volcanic glass (percent) is 30 or more.
of the time (cumulative) when the soil temperature at a depth                                              Vitrixerandic Gypsiargids
of 50 cm below the soil surface is 5 oC or higher and have a soil
moisture regime that borders on xeric.                               GEDD. Other Gypsiargids that have, throughout one or more
                                                Xeric Calciargids    horizons with a total thickness of 18 cm or more within 75 cm
                                                                     of the soil surface, one or both of the following:
GEEP.    Other Calciargids that, in normal years, are dry in all
100                                                                                                           Keys to Soil Taxonomy



   1. More than 35 percent (by volume) fragments coarser               soil surface is 5 oC or higher and a soil moisture regime that
   than 2.0 mm, of which more than 66 percent is cinders,              borders on ustic.
   pumice, and pumicelike fragments; or                                                                      Lithic Ustic Haplargids
   2. A fine-earth fraction containing 30 percent or more
                                                                     GEFD. Other Haplargids that have a lithic contact within 50
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                                                     cm of the soil surface.
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
                                                                                                                Lithic Haplargids
   by ammonium oxalate) times 60] plus the volcanic glass
   (percent) is 30 or more.
                                                                     GEFE. Other Haplargids that have both:
                                          Vitrandic Gypsiargids
                                                                       1.    One or both of the following:
GEDE. Other Gypsiargids that, in normal years, are dry in all
                                                                            a. Cracks within 125 cm of the soil surface that are 5
parts of the moisture control section for less than three-fourths
                                                                            mm or more wide through a thickness of 30 cm or more
of the time (cumulative) when the soil temperature at a depth
                                                                            for some time in normal years and slickensides or wedge-
of 50 cm below the soil surface is 5 oC or higher and have a soil
                                                                            shaped peds in a layer 15 cm or more thick that has its
moisture regime that borders on xeric.
                                                                            upper boundary within 125 cm of the soil surface; or
                                                Xeric Gypsiargids
                                                                            b. A linear extensibility of 6.0 cm or more between the
GEDF. Other Gypsiargids that, in normal years, are dry in all               soil surface and either a depth of 100 cm or a densic,
parts of the moisture control section for less than three-fourths           lithic, or paralithic contact if shallower; and
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the soil surface is 5 oC or higher and have a soil      2. A moisture control section that, in normal years, is dry in
moisture regime that borders on ustic.                                 all parts for less than three-fourths of the time (cumulative)
                                                Ustic Gypsiargids      when the soil temperature at a depth of 50 cm below the
                                                                       soil surface is 5 oC or higher and a soil moisture regime that
GEDG. Other Gypsiargids.                                               borders on xeric.
                                             Typic Gypsiargids                                                    Xerertic Haplargids

                                                                     GEFF. Other Haplargids that have both:
Haplargids
                                                                       1.    One or both of the following:
Key to Subgroups
GEFA. Haplargids that have both:                                            a. Cracks within 125 cm of the soil surface that are 5
                                                                            mm or more wide through a thickness of 30 cm or more
   1. A lithic contact within 50 cm of the soil surface; and                for some time in normal years and slickensides or wedge-
   2. An argillic horizon that is discontinuous throughout each             shaped peds in a layer 15 cm or more thick that has its
   pedon.                                                                   upper boundary within 125 cm of the soil surface; or
                               Lithic Ruptic-Entic Haplargids               b. A linear extensibility of 6.0 cm or more between the
                                                                            soil surface and either a depth of 100 cm or a densic,
GEFB.    Other Haplargids that have both:                                   lithic, or paralithic contact if shallower; and
   1. A lithic contact within 50 cm of the soil surface; and           2. A moisture control section that, in normal years, is dry in
                                                                       all parts for less than three-fourths of the time (cumulative)
   2. A moisture control section that, in normal years, is dry in
                                                                       when the soil temperature at a depth of 50 cm below the
   all parts for less than three-fourths of the time (cumulative)
                                                                       soil surface is 5 oC or higher and a soil moisture regime that
   when the soil temperature at a depth of 50 cm below the
                                                                       borders on ustic.
   soil surface is 5 oC or higher and a soil moisture regime that
                                                                                                                   Ustertic Haplargids
   borders on xeric.
                                          Lithic Xeric Haplargids
                                                                     GEFG. Other Haplargids that have one or both of the
                                                                     following:
GEFC. Other Haplargids that have both:
                                                                       1. Cracks within 125 cm of the soil surface that are 5 mm
   1. A lithic contact within 50 cm of the soil surface; and
                                                                       or more wide through a thickness of 30 cm or more for some
   2. A moisture control section that, in normal years, is dry in      time in normal years and slickensides or wedge-shaped peds
   all parts for less than three-fourths of the time (cumulative)      in a layer 15 cm or more thick that has its upper boundary
   when the soil temperature at a depth of 50 cm below the             within 125 cm of the soil surface; or
Aridisols                                                                                                                           101



   2. A linear extensibility of 6.0 cm or more between the soil         1. One or more horizons, within 100 cm of the soil
   surface and either a depth of 100 cm or a densic, lithic, or         surface and with a combined thickness of 15 cm or more,
   paralithic contact if shallower.                                     that contain 20 percent or more (by volume) nodules or
                                              Vertic Haplargids         concretions; and
                                                                        2. A moisture control section that, in normal years, is dry in
GEFH.       Other Haplargids that are either:
                                                                        all parts for less than three-fourths of the time (cumulative)
   1. Irrigated and have aquic conditions for some time in              when the soil temperature at a depth of 50 cm below the
   normal years in one or more layers within 100 cm of the soil         soil surface is 5 oC or higher and a soil moisture regime that
   surface; or                                                          borders on ustic.
                                                                                                          Petronodic Ustic Haplargids
   2. Saturated with water in one or more layers within 100
   cm of the soil surface for 1 month or more in normal years.       GEFN. Other Haplargids that have one or more horizons,
                                             Aquic Haplargids        within 100 cm of the soil surface and with a combined thickness
                                                                     of 15 cm or more, that contain 20 percent or more (by volume)
GEFI.   Other Haplargids that:                                       nodules or concretions.
   1. Meet sandy or sandy-skeletal particle-size class criteria                                              Petronodic Haplargids
   throughout a layer extending from the soil surface to the top                                                                          A
                                                                     GEFO. Other Haplargids that have both:                               R
   of an argillic horizon at a depth of 50 cm or more; and                                                                                I

   2. Have a moisture control section that, in normal years,            1. A moisture control section that, in normal years, is dry in
   is dry in all parts for less than three-fourths of the time          all parts for less than three-fourths of the time (cumulative)
   (cumulative) when the soil temperature at a depth of 50 cm           when the soil temperature at a depth of 50 cm below the
   below the soil surface is 5 oC or higher and a soil moisture         soil surface is 5 oC or higher and a soil moisture regime that
   regime that borders on ustic.                                        borders on xeric; and
                                          Arenic Ustic Haplargids       2. Throughout one or more horizons with a total thickness
                                                                        of 18 cm or more within 75 cm of the soil surface, one or
GEFJ. Other Haplargids that meet sandy or sandy-skeletal                both of the following:
particle-size class criteria throughout a layer extending from the
soil surface to the top of an argillic horizon at a depth of 50 cm         a. More than 35 percent (by volume) fragments coarser
or more.                                                                   than 2.0 mm, of which more than 66 percent is cinders,
                                                Arenic Haplargids          pumice, and pumicelike fragments; or
                                                                           b. A fine-earth fraction containing 30 percent or more
GEFK.       Other Haplargids that have both:                               particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                                                           or more is volcanic glass, and [(Al plus 1/2 Fe, percent
   1. One or more horizons, within 100 cm of the soil surface
                                                                           extracted by ammonium oxalate) times 60] plus the
   and with a combined thickness of 15 cm or more, that
                                                                           volcanic glass (percent) is 30 or more.
   contain 20 percent or more (by volume) durinodes or are
                                                                                                            Vitrixerandic Haplargids
   brittle and have at least a firm rupture-resistance class when
   moist; and
                                                                     GEFP. Other Haplargids that have, throughout one or more
   2. A moisture control section that, in normal years, is dry in    horizons with a total thickness of 18 cm or more within 75 cm
   all parts for less than three-fourths of the time (cumulative)    of the soil surface, one or both of the following:
   when the soil temperature at a depth of 50 cm below the
                                                                        1. More than 35 percent (by volume) fragments coarser
   soil surface is 5 oC or higher and a soil moisture regime that
                                                                        than 2.0 mm, of which more than 66 percent is cinders,
   borders on xeric.
                                                                        pumice, and pumicelike fragments; or
                                     Durinodic Xeric Haplargids
                                                                        2. A fine-earth fraction containing 30 percent or more
GEFL. Other Haplargids that have one or more horizons,                  particles 0.02 to 2.0 mm in diameter, of which 5 percent or
within 100 cm of the soil surface and with a combined thickness         more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
of 15 cm or more, that contain 20 percent or more (by volume)           by ammonium oxalate) times 60] plus the volcanic glass
durinodes or are brittle and have at least a firm rupture-              (percent) is 30 or more.
resistance class when moist.                                                                                    Vitrandic Haplargids
                                            Durinodic Haplargids
                                                                     GEFQ. Other Haplargids that, in normal years, are dry in all
GEFM.       Other Haplargids that have both:                         parts of the moisture control section for less than three-fourths
102	                                                                                                           Keys	to	Soil	Taxonomy



of	the	time	(cumulative)	when	the	soil	temperature	at	a	depth	             shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	
of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	         upper	boundary	within	125	cm	of	the	soil	surface;	or
moisture	regime	that	borders	on	xeric.
                                                                           b.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	
                                               Xeric Haplargids
                                                                           soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	
                                                                           lithic,	or	paralithic	contact,	whichever	is	shallower.
GEFR.	 Other	Haplargids	that,	in	normal	years,	are	dry	in	all	
                                                                                                                  Xerertic Natrargids
parts	of	the	moisture	control	section	for	less	than	three-fourths	
of	the	time	(cumulative)	when	the	soil	temperature	at	a	depth	
of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	    GEBE.	 Other	Natrargids	that:
moisture	regime	that	borders	on	ustic.                                  1.	 In	normal	years,	are	dry	in	all	parts	of	the	moisture	
                                                 Ustic Haplargids       control	section	for	less	than	three-fourths	of	the	time	
                                                                        (cumulative)	when	the	soil	temperature	at	a	depth	of	50	
GEFS.	 Other	Haplargids.                                                cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
                                               Typic Haplargids         moisture	regime	that	borders	on	ustic;	and

Natrargids                                                              2.	 Have	one or both	of	the	following:

Key to Subgroups                                                           a.	 Cracks	within	125	cm	of	the	soil	surface	that	are	5	
                                                                           mm	or	more	wide	through	a	thickness	of	30	cm	or	more	
GEBA.	 Natrargids	that	have	both:                                          for	some	time	in	most	years	and	slickensides	or	wedge-
   1.	 A	lithic	contact	within	50	cm	of	the	soil	surface;	and              shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	
                                                                           upper	boundary	within	125	cm	of	the	soil	surface;	or
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	         b.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	                soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	         lithic,	or	paralithic	contact,	whichever	is	shallower.
   borders	on	xeric.                                                                                               Ustertic Natrargids
                                          Lithic Xeric Natrargids
                                                                      GEBF.	 Other	Natrargids	that	have	one or both	of	the	
GEBB.	 Other	Natrargids	that	have	both:                               following:

   1.	 A	lithic	contact	within	50	cm	of	the	soil	surface;	and           1.	 Cracks	within	125	cm	of	the	soil	surface	that	are	5	mm	
                                                                        or	more	wide	through	a	thickness	of	30	cm	or	more	for	some	
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	     time	in	normal	years	and	slickensides	or	wedge-shaped	peds	
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	      in	a	layer	15	cm	or	more	thick	that	has	its	upper	boundary	
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	             within	125	cm	of	the	soil	surface;	or
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	
   borders	on	ustic.                                                    2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	soil	
                                           Lithic Ustic Natrargids      surface	and	either	a	depth	of	100	cm	or	a	densic,	lithic,	or	
                                                                        paralithic	contact,	whichever	is	shallower.
GEBC.	 Other	Natrargids	that	have	a	lithic	contact	within	50	                                                       Vertic Natrargids
cm	of	the	soil	surface.
                                            Lithic Natrargids         GEBG.	 Other	Natrargids	that	are	either:
                                                                        1.	 Irrigated	and	have	aquic	conditions	for	some	time	in	
GEBD.	 Other	Natrargids	that:
                                                                        normal	years	in	one	or	more	layers	within	100	cm	of	the	soil	
   1.	 In	normal	years,	are	dry	in	all	parts	of	the	moisture	           surface;	or
   control	section	for	less	than	three-fourths	of	the	time	
                                                                        2.	 Saturated	with	water	in	one	or	more	layers	within	100	
   (cumulative)	when	the	soil	temperature	at	a	depth	of	50	
                                                                        cm	of	the	soil	surface	for	1	month	or	more	in	normal	years.
   cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
                                                                                                                   Aquic Natrargids
   moisture	regime	that	borders	on	xeric;	and
   2.	 Have	one or both	of	the	following:                             GEBH.	 Other	Natrargids	that	have	both:
       a.	 Cracks	within	125	cm	of	the	soil	surface	that	are	5	         1.	 One	or	more	horizons,	within	100	cm	of	the	soil	surface	
       mm	or	more	wide	through	a	thickness	of	30	cm	or	more	            and	with	a	combined	thickness	of	15	cm	or	more,	that	
       for	some	time	in	most	years	and	slickensides	or	wedge-           contain	20	percent	or	more	(by	volume)	durinodes	or	are	
Aridisols                                                                                                                         103



  brittle and have at least a firm rupture-resistance class when      soil surface is 5 oC or higher and a soil moisture regime that
  moist; and                                                          borders on xeric.
                                                                                                           Haploxeralfic Natrargids
  2. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)
                                                                   GEBN. Other Natrargids that have an exchangeable sodium
  when the soil temperature at a depth of 50 cm below the
                                                                   percentage of less than 15 (or an SAR of less than 13) in 50
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                   percent or more of the natric horizon.
  borders on xeric.
                                                                                                                Haplic Natrargids
                                     Durinodic Xeric Natrargids
                                                                   GEBO. Other Natrargids that have both:
GEBI. Other Natrargids that have one or more horizons,
within 100 cm of the soil surface and with a combined thickness       1. A moisture control section that, in normal years, is dry in
of 15 cm or more, that contain 20 percent or more (by volume)         all parts for less than three-fourths of the time (cumulative)
durinodes or are brittle and have at least a firm rupture-            when the soil temperature at a depth of 50 cm below the
resistance class when moist.                                          soil surface is 5 oC or higher and a soil moisture regime that
                                            Durinodic Natrargids      borders on xeric; and
                                                                      2. Throughout one or more horizons with a total thickness
GEBJ. Other Natrargids that have one or more horizons,                                                                                  A
                                                                      of 18 cm or more within 75 cm of the soil surface, one or         R
within 100 cm of the soil surface and with a combined thickness
                                                                      both of the following:                                            I
of 15 cm or more, that contain 20 percent or more (by volume)
nodules or concretions.                                                  a. More than 35 percent (by volume) fragments coarser
                                         Petronodic Natrargids           than 2.0 mm, of which more than 66 percent is cinders,
                                                                         pumice, and pumicelike fragments; or
GEBK. Other Natrargids that have both:
                                                                         b. A fine-earth fraction containing 30 percent or more
  1. Skeletans covering 10 percent or more of the surfaces of            particles 0.02 to 2.0 mm in diameter, of which 5 percent
  peds at a depth of 2.5 cm or more below the upper boundary             or more is volcanic glass, and [(Al plus 1/2 Fe, percent
  of the natric horizon; and                                             extracted by ammonium oxalate) times 60] plus the
                                                                         volcanic glass (percent) is 30 or more.
  2. A moisture control section that, in normal years, is dry in
                                                                                                          Vitrixerandic Natrargids
  all parts for less than three-fourths of the time (cumulative)
  when the soil temperature at a depth of 50 cm below the
                                                                   GEBP. Other Natrargids that have, throughout one or more
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                   horizons with a total thickness of 18 cm or more within 75 cm
  borders on ustic.
                                                                   of the soil surface, one or both of the following:
                                        Glossic Ustic Natrargids
                                                                      1. More than 35 percent (by volume) fragments coarser
GEBL.       Other Natrargids that have both:                          than 2.0 mm, of which more than 66 percent is cinders,
  1. An exchangeable sodium percentage of less than 15 (or            pumice, and pumicelike fragments; or
  an SAR of less than 13) in 50 percent or more of the natric         2. A fine-earth fraction containing 30 percent or more
  horizon; and                                                        particles 0.02 to 2.0 mm in diameter, of which 5 percent or
  2. A moisture control section that, in normal years, is dry in      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
  all parts for less than three-fourths of the time (cumulative)      by ammonium oxalate) times 60] plus the volcanic glass
  when the soil temperature at a depth of 50 cm below the             (percent) is 30 or more.
  soil surface is 5 oC or higher and a soil moisture regime that                                               Vitrandic Natrargids
  borders on ustic.
                                         Haplic Ustic Natrargids   GEBQ. Other Natrargids that, in normal years, are dry in all
                                                                   parts of the moisture control section for less than three-fourths
GEBM.       Other Natrargids that have both:                       of the time (cumulative) when the soil temperature at a depth
                                                                   of 50 cm below the soil surface is 5 oC or higher and have a soil
  1. An exchangeable sodium percentage of less than 15 (or         moisture regime that borders on xeric.
  an SAR of less than 13) in 50 percent or more of the natric                                                       Xeric Natrargids
  horizon; and
  2. A moisture control section that, in normal years, is dry in   GEBR. Other Natrargids that, in normal years, are dry in all
  all parts for less than three-fourths of the time (cumulative)   parts of the moisture control section for less than three-fourths
  when the soil temperature at a depth of 50 cm below the          of the time (cumulative) when the soil temperature at a depth
104                                                                                                               Keys to Soil Taxonomy



of 50 cm below the soil surface is 5 oC or higher and have a soil      GECE. Other Paleargids that have a calcic horizon within 150
moisture regime that borders on ustic.                                 cm of the soil surface.
                                               Ustic Natrargids                                                   Calcic Paleargids

GEBS. Other Natrargids that have skeletans covering 10                 GECF. Other Paleargids that have both:
percent or more of the surfaces of peds at a depth of 2.5 cm or
                                                                         1. One or more horizons, within 100 cm of the soil surface
more below the upper boundary of the natric horizon.
                                                                         and with a combined thickness of 15 cm or more, that
                                              Glossic Natrargids
                                                                         contain 20 percent or more (by volume) durinodes or are
                                                                         brittle and have at least a firm rupture-resistance class when
GEBT. Other Natrargids.                                                  moist; and
                                                Typic Natrargids
                                                                         2. A moisture control section that, in normal years, is dry in
Paleargids                                                               all parts for less than three-fourths of the time (cumulative)
                                                                         when the soil temperature at a depth of 50 cm below the
Key to Subgroups                                                         soil surface is 5 oC or higher and a soil moisture regime that
GECA.     Paleargids that have one or both of the following:             borders on xeric.
                                                                                                            Durinodic Xeric Paleargids
   1. Cracks within 125 cm of the soil surface that are 5 mm
   or more wide through a thickness of 30 cm or more for some          GECG. Other Paleargids that have one or more horizons,
   time in normal years and slickensides or wedge-shaped peds          within 100 cm of the soil surface and with a combined thickness
   in a layer 15 cm or more thick that has its upper boundary          of 15 cm or more, that contain 20 percent or more (by volume)
   within 125 cm of the soil surface; or                               durinodes or are brittle and have at least a firm rupture-
   2. A linear extensibility of 6.0 cm or more between the soil        resistance class when moist.
   surface and either a depth of 100 cm or a densic, lithic, or                                                    Durinodic Paleargids
   paralithic contact, whichever is shallower.
                                               Vertic Paleargids       GECH. Other Paleargids that have both:
                                                                         1. One or more horizons, within 100 cm of the soil
GECB.     Other Paleargids that are either:                              surface and with a combined thickness of 15 cm or more,
   1. Irrigated and have aquic conditions for some time in               that contain 20 percent or more (by volume) nodules or
   normal years in one or more layers within 100 cm of the soil          concretions; and
   surface; or                                                           2. A moisture control section that, in normal years, is dry in
   2. Saturated with water in one or more layers within 100              all parts for less than three-fourths of the time (cumulative)
   cm of the soil surface for 1 month or more in normal years.           when the soil temperature at a depth of 50 cm below the
                                              Aquic Paleargids           soil surface is 5 oC or higher and a soil moisture regime that
                                                                         borders on ustic.
GECC.     Other Paleargids that:                                                                            Petronodic Ustic Paleargids

   1. Meet sandy or sandy-skeletal particle-size class criteria        GECI. Other Paleargids that have one or more horizons,
   throughout a layer extending from the mineral soil surface          within 100 cm of the soil surface and with a combined thickness
   to the top of an argillic horizon at a depth of 50 cm or more;      of 15 cm or more, that contain 20 percent or more (by volume)
   and                                                                 nodules or concretions.
   2. Have a moisture control section that, in normal years,                                                    Petronodic Paleargids
   is dry in all parts for less than three-fourths of the time
   (cumulative) when the soil temperature at a depth of 50 cm          GECJ.   Other Paleargids that have both:
   below the soil surface is 5 oC or higher and a soil moisture          1. A moisture control section that, in normal years, is dry in
   regime that borders on ustic.                                         all parts for less than three-fourths of the time (cumulative)
                                           Arenic Ustic Paleargids       when the soil temperature at a depth of 50 cm below the
                                                                         soil surface is 5 oC or higher and a soil moisture regime that
GECD. Other Paleargids that meet sandy or sandy-skeletal                 borders on xeric; and
particle-size class criteria throughout a layer extending from the
mineral soil surface to the top of an argillic horizon at a depth of     2. Throughout one or more horizons with a total thickness
50 cm or more.                                                           of 18 cm or more within 75 cm of the soil surface, one or
                                                 Arenic Paleargids       both of the following:
Aridisols                                                                                                                           105



      a. More than 35 percent (by volume) fragments coarser          GEAB. Other Petroargids that have a petrogypsic horizon
      than 2.0 mm, of which more than 66 percent is cinders,         within 150 cm of the soil surface.
      pumice, and pumicelike fragments; or                                                               Petrogypsic Petroargids
      b. A fine-earth fraction containing 30 percent or more         GEAC. Other Petroargids that have both:
      particles 0.02 to 2.0 mm in diameter, of which 5 percent
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent          1. A duripan within 150 cm of the soil surface; and
      extracted by ammonium oxalate) times 60] plus the                 2. A moisture control section that, in normal years, is dry in
      volcanic glass (percent) is 30 or more.                           all parts for less than three-fourths of the time (cumulative)
                                        Vitrixerandic Paleargids        when the soil temperature at a depth of 50 cm below the
                                                                        soil surface is 5 oC or higher and a soil moisture regime that
GECK. Other Paleargids that have, throughout one or more                borders on xeric.
horizons with a total thickness of 18 cm or more within 75 cm                                                  Duric Xeric Petroargids
of the soil surface, one or both of the following:
   1. More than 35 percent (by volume) fragments coarser             GEAD. Other Petroargids that have a duripan within 150 cm
   than 2.0 mm, of which more than 66 percent is cinders,            of the soil surface.
   pumice, and pumicelike fragments; or                                                                        Duric Petroargids
                                                                                                                                          A
                                                                                                                                          R
   2. A fine-earth fraction containing 30 percent or more            GEAE. Other Petroargids that have a natric horizon.                  I
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or                                                 Natric Petroargids
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
   by ammonium oxalate) times 60] plus the volcanic glass            GEAF. Other Petroargids that, in normal years, are dry in all
   (percent) is 30 or more.                                          parts of the moisture control section for less than three-fourths
                                            Vitrandic Paleargids     of the time (cumulative) when the soil temperature at a depth
                                                                     of 50 cm below the soil surface is 5 oC or higher and have a soil
GECL. Other Paleargids that, in normal years, are dry in all         moisture regime that borders on xeric.
parts of the moisture control section for less than three-fourths                                                    Xeric Petroargids
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the surface is 5 oC or higher and have a soil
                                                                     GEAG. Other Petroargids that, in normal years, are dry in all
moisture regime that borders on xeric.
                                                                     parts of the moisture control section for less than three-fourths
                                                 Xeric Paleargids
                                                                     of the time (cumulative) when the soil temperature at a depth
                                                                     of 50 cm below the soil surface is 5 oC or higher and have a soil
GECM. Other Paleargids that, in normal years, are dry in all
                                                                     moisture regime that borders on ustic.
parts of the moisture control section for less than three-fourths
                                                                                                                      Ustic Petroargids
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the surface is 5 oC or higher and have a soil
                                                                     GEAH. Other Petroargids.
moisture regime that borders on ustic.
                                                                                                                   Typic Petroargids
                                                  Ustic Paleargids

GECN.       Other Paleargids.                                        Calcids
                                               Typic Paleargids
                                                                     Key to Great Groups
Petroargids                                                          GFA. Calcids that have a petrocalcic horizon within 100 cm of
Key to Subgroups                                                     the soil surface.
                                                                                                               Petrocalcids, p. 107
GEAA.       Petroargids that have both:
   1. A petrogypsic horizon within 150 cm of the soil surface;       GFB. Other Calcids.
   and                                                                                                           Haplocalcids, p. 105

   2. A moisture control section that, in normal years, is dry in    Haplocalcids
   all parts for less than three-fourths of the time (cumulative)
   when the soil temperature at a depth of 50 cm below the           Key to Subgroups
   surface is 5 oC or higher and a soil moisture regime that
                                                                     GFBA. Haplocalcids that have both:
   borders on ustic.
                                    Petrogypsic Ustic Petroargids       1. A lithic contact within 50 cm of the soil surface; and
106                                                                                                         Keys to Soil Taxonomy



  2. A moisture control section that, in normal years, is dry in     normal years in one or more layers within 100 cm of the soil
  all parts for less than three-fourths of the time (cumulative)     surface; or
  when the soil temperature at a depth of 50 cm below the
                                                                     2. Saturated with water in one or more layers within 100
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                     cm of the soil surface for 1 month or more in normal years.
  borders on xeric.
                                                                                                             Aquic Haplocalcids
                                       Lithic Xeric Haplocalcids
                                                                   GFBG. Other Haplocalcids that have both:
GFBB. Other Haplocalcids that have both:
                                                                     1. A duripan within 150 cm of the soil surface; and
  1. A lithic contact within 50 cm of the soil surface; and
                                                                     2. A moisture control section that, in normal years, is dry in
  2. A moisture control section that, in normal years, is dry in
                                                                     all parts for less than three-fourths of the time (cumulative)
  all parts for less than three-fourths of the time (cumulative)
                                                                     when the soil temperature at a depth of 50 cm below the
  when the soil temperature at a depth of 50 cm below the
                                                                     soil surface is 5 oC or higher and a soil moisture regime that
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                     borders on xeric.
  borders on ustic.
                                                                                                          Duric Xeric Haplocalcids
                                       Lithic Ustic Haplocalcids
                                                                   GFBH. Other Haplocalcids that have a duripan within 150 cm
GFBC. Other Haplocalcids that have a lithic contact within 50
                                                                   of the soil surface.
cm of the soil surface.
                                                                                                          Duric Haplocalcids
                                         Lithic Haplocalcids
                                                                   GFBI. Other Haplocalcids that have both:
GFBD. Other Haplocalcids that have one or both of the
following:                                                           1. One or more horizons, within 100 cm of the soil surface
                                                                     and with a combined thickness of 15 cm or more, that
  1. Cracks within 125 cm of the soil surface that are 5 mm
                                                                     contain 20 percent or more (by volume) durinodes or are
  or more wide through a thickness of 30 cm or more for some
                                                                     brittle and have at least a firm rupture-resistance class when
  time in normal years and slickensides or wedge-shaped peds
                                                                     moist; and
  in a layer 15 cm or more thick that has its upper boundary
  within 125 cm of the soil surface; or                              2. A moisture control section that, in normal years, is dry in
                                                                     all parts for less than three-fourths of the time (cumulative)
  2. A linear extensibility of 6.0 cm or more between the soil
                                                                     when the soil temperature at a depth of 50 cm below the
  surface and either a depth of 100 cm or a densic, lithic, or
                                                                     soil surface is 5 oC or higher and a soil moisture regime that
  paralithic contact, whichever is shallower.
                                                                     borders on xeric.
                                           Vertic Haplocalcids
                                                                                                     Durinodic Xeric Haplocalcids
GFBE. Other Haplocalcids that:
                                                                   GFBJ. Other Haplocalcids that have one or more horizons,
  1. Are either:                                                   within 100 cm of the soil surface and with a combined thickness
                                                                   of 15 cm or more, that contain 20 percent or more (by volume)
       a. Irrigated and have aquic conditions for some time in
                                                                   durinodes or are brittle and have at least a firm rupture-
       normal years in one or more layers within 100 cm of the
                                                                   resistance class when moist.
       soil surface; or
                                                                                                            Durinodic Haplocalcids
       b. Saturated with water in one or more layers within
       100 cm of the soil surface for 1 month or more in normal    GFBK. Other Haplocalcids that have both:
       years; and
                                                                     1. One or more horizons, within 100 cm of the soil
  2. Have one or more horizons, within 100 cm of the soil            surface and with a combined thickness of 15 cm or more,
  surface and with a combined thickness of 15 cm or more,            that contain 20 percent or more (by volume) nodules or
  that contain 20 percent or more (by volume) durinodes or are       concretions; and
  brittle and have at least a firm rupture-resistance class when
                                                                     2. A moisture control section that, in normal years, is dry in
  moist.
                                                                     all parts for less than three-fourths of the time (cumulative)
                                  Aquic Durinodic Haplocalcids
                                                                     when the soil temperature at a depth of 50 cm below the
                                                                     soil surface is 5 oC or higher and a soil moisture regime that
GFBF.    Other Haplocalcids that are either:
                                                                     borders on xeric.
  1.    Irrigated and have aquic conditions for some time in                                         Petronodic Xeric Haplocalcids
Aridisols                                                                                                                          107



GFBL.       Other Haplocalcids that have both:                        when the soil temperature at a depth of 50 cm below the
                                                                      soil surface is 5 oC or higher and a soil moisture regime that
  1. One or more horizons, within 100 cm of the soil
                                                                      borders on xeric; and
  surface and with a combined thickness of 15 cm or more,
  that contain 20 percent or more (by volume) nodules or              2. Throughout one or more horizons with a total thickness
  concretions; and                                                    of 18 cm or more within 75 cm of the soil surface, one or
                                                                      both of the following:
  2. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)           a. More than 35 percent (by volume) fragments coarser
  when the soil temperature at a depth of 50 cm below the                  than 2.0 mm, of which more than 66 percent is cinders,
  soil surface is 5 oC or higher and a soil moisture regime that           pumice, and pumicelike fragments; or
  borders on ustic.
                                                                           b. A fine-earth fraction containing 30 percent or more
                                  Petronodic Ustic Haplocalcids
                                                                           particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                                                           or more is volcanic glass, and [(Al plus 1/2 Fe, percent
GFBM. Other Haplocalcids that have one or more horizons,
                                                                           extracted by ammonium oxalate) times 60] plus the
within 100 cm of the soil surface and with a combined thickness
                                                                           volcanic glass (percent) is 30 or more.
of 15 cm or more, that contain 20 percent or more (by volume)
nodules or concretions.                                                                                   Vitrixerandic Haplocalcids
                                      Petronodic Haplocalcids                                                                            A
                                                                   GFBR. Other Haplocalcids that have, throughout one or more            R
                                                                                                                                         I
                                                                   horizons with a total thickness of 18 cm or more within 75 cm
GFBN. Other Haplocalcids that have both:
                                                                   of the soil surface, one or both of the following:
  1. A horizon at least 25 cm thick within 100 cm of the soil
                                                                      1. More than 35 percent (by volume) fragments coarser
  surface that has an exchangeable sodium percentage of 15 or
                                                                      than 2.0 mm, of which more than 66 percent is cinders,
  more (or an SAR of 13 or more) during at least 1 month in
                                                                      pumice, and pumicelike fragments; or
  normal years; and
                                                                      2. A fine-earth fraction containing 30 percent or more
  2. A moisture control section that, in normal years, is dry in
                                                                      particles 0.02 to 2.0 mm in diameter, of which 5 percent or
  all parts for less than three-fourths of the time (cumulative)
                                                                      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
  when the soil temperature at a depth of 50 cm below the
                                                                      by ammonium oxalate) times 60] plus the volcanic glass
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                      (percent) is 30 or more.
  borders on xeric.
                                                                                                            Vitrandic Haplocalcids
                                        Sodic Xeric Haplocalcids

GFBO. Other Haplocalcids that have both:                           GFBS. Other Haplocalcids that, in normal years, are dry in all
                                                                   parts of the moisture control section for less than three-fourths
  1. A horizon at least 25 cm thick within 100 cm of the soil      of the time (cumulative) when the soil temperature at a depth
  surface that has an exchangeable sodium percentage of 15 or      of 50 cm below the soil surface is 5 oC or higher and have a soil
  more (or an SAR of 13 or more) during at least 1 month in        moisture regime that borders on xeric.
  normal years; and                                                                                              Xeric Haplocalcids
  2. A moisture control section that, in normal years, is dry in
                                                                   GFBT. Other Haplocalcids that, in normal years, are dry in all
  all parts for less than three-fourths of the time (cumulative)
                                                                   parts of the moisture control section for less than three-fourths
  when the soil temperature at a depth of 50 cm below the
                                                                   of the time (cumulative) when the soil temperature at a depth
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                   of 50 cm below the soil surface is 5 oC or higher and have a soil
  borders on ustic.
                                                                   moisture regime that borders on ustic.
                                        Sodic Ustic Haplocalcids
                                                                                                                  Ustic Haplocalcids
GFBP. Other Haplocalcids that have, in a horizon at least
                                                                   GFBU. Other Haplocalcids.
25 cm thick within 100 cm of the mineral soil surface, an
                                                                                                                Typic Haplocalcids
exchangeable sodium percentage of 15 or more (or an SAR of
13 or more) during at least 1 month in normal years.
                                           Sodic Haplocalcids      Petrocalcids
                                                                   Key to Subgroups
GFBQ.       Other Haplocalcids that have both:
                                                                   GFAA. Petrocalcids that are either:
  1. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)      1.    Irrigated and have aquic conditions for some time in
108                                                                                                             Keys to Soil Taxonomy



   normal years in one or more layers within 100 cm of the soil       of the time (cumulative) when the soil temperature at a depth
   surface; or                                                        of 50 cm below the soil surface is 5 oC or higher and have a soil
                                                                      moisture regime that borders on ustic.
   2. Saturated with water in one or more layers within 100                                                         Ustic Petrocalcids
   cm of the soil surface for 1 month or more in normal years.
                                            Aquic Petrocalcids        GFAJ. Other Petrocalcids.
                                                                                                                   Typic Petrocalcids
GFAB.    Other Petrocalcids that have a natric horizon.
                                             Natric Petrocalcids
                                                                      Cambids
GFAC. Other Petrocalcids that have both:
                                                                      Key to Great Groups
   1. An argillic horizon within 100 cm of the soil surface;
   and                                                                GGA. Cambids that are either:

   2. A moisture control section that, in normal years, is dry in        1. Irrigated and have aquic conditions for some time in
   all parts for less than three-fourths of the time (cumulative)        normal years in one or more layers within 100 cm of the soil
   when the soil temperature at a depth of 50 cm below the               surface; or
   soil surface is 5 oC or higher and a soil moisture regime that
                                                                         2. Saturated with water in one or more layers within 100
   borders on xeric.                                                     cm of the soil surface for 1 month or more in normal years.
                                              Xeralfic Petrocalcids                                             Aquicambids, p. 108
GFAD.    Other Petrocalcids that have both:
                                                                      GGB. Other Cambids that have a duripan or a petrocalcic or
   1. An argillic horizon within 100 cm of the soil surface;          petrogypsic horizon within 150 cm of the soil surface.
   and                                                                                                         Petrocambids, p. 112
   2. A moisture control section that, in normal years, is dry in
                                                                      GGC. Other Cambids that have an anthropic epipedon.
   all parts for less than three-fourths of the time (cumulative)
                                                                                                         Anthracambids, p. 108
   when the soil temperature at a depth of 50 cm below the
   soil surface is 5 oC or higher and a soil moisture regime that
                                                                      GGD. Other Cambids.
   borders on ustic.
                                                                                                                Haplocambids, p. 109
                                              Ustalfic Petrocalcids

GFAE. Other Petrocalcids that have an argillic horizon within         Anthracambids
100 cm of the soil surface.                                           Key to Subgroups
                                          Argic Petrocalcids
                                                                      GGCA. All Anthracambids.
GFAF.    Other Petrocalcids that have both:                                                                     Typic Anthracambids

   1. A calcic horizon overlying the petrocalcic horizon; and         Aquicambids
   2. A lithic contact within 50 cm of the soil surface.              Key to Subgroups
                                    Calcic Lithic Petrocalcids
                                                                      GGAA. Aquicambids that have, in a horizon at least 25 cm
GFAG. Other Petrocalcids that have a calcic horizon overlying         thick within 100 cm of the soil surface, an exchangeable sodium
the petrocalcic horizon.                                              percentage of 15 or more (or an SAR of 13 or more) during at
                                         Calcic Petrocalcids          least 1 month in normal years.
                                                                                                                   Sodic Aquicambids
GFAH. Other Petrocalcids that, in normal years, are dry in all
parts of the moisture control section for less than three-fourths     GGAB. Other Aquicambids that have both:
of the time (cumulative) when the soil temperature at a depth            1. One or more horizons, within 100 cm of the soil surface
of 50 cm below the soil surface is 5 oC or higher and have a soil        and with a combined thickness of 15 cm or more, that
moisture regime that borders on xeric.                                   contain 20 percent or more (by volume) durinodes or are
                                                Xeric Petrocalcids       brittle and have at least a firm rupture-resistance class when
                                                                         moist; and
GFAI. Other Petrocalcids that, in normal years, are dry in all
parts of the moisture control section for less than three-fourths        2. A moisture control section that, in normal years, is dry in
Aridisols                                                                                                                          109



  all parts for less than three-fourths of the time (cumulative)    GGAG. Other Aquicambids that have an irregular decrease in
  when the soil temperature at a depth of 50 cm below the           organic-carbon content (Holocene age) between a depth of 25
  soil surface is 5 oC or higher and a soil moisture regime that    cm and either a depth of 125 cm below the mineral soil surface
  borders on xeric.                                                 or a densic, lithic, or paralithic contact, whichever is shallower.
                                  Durinodic Xeric Aquicambids                                                   Fluventic Aquicambids

GGAC. Other Aquicambids that have one or more horizons,             GGAH. Other Aquicambids that, in normal years, are dry
within 100 cm of the soil surface and with a combined thickness     in all parts of the moisture control section for less than three-
of 15 cm or more, that contain 20 percent or more (by volume)       fourths of the time (cumulative) when the soil temperature at a
durinodes or are brittle and have at least a firm rupture-          depth of 50 cm below the soil surface is 5 oC or higher and have
resistance class when moist.                                        a soil moisture regime that borders on xeric.
                                         Durinodic Aquicambids                                                     Xeric Aquicambids

GGAD. Other Aquicambids that have one or more horizons,             GGAI. Other Aquicambids that, in normal years, are dry in all
within 100 cm of the soil surface and with a combined thickness     parts of the moisture control section for less than three-fourths
of 15 cm or more, that contain 20 percent or more (by volume)       of the time (cumulative) when the soil temperature at a depth
nodules or concretions.                                             of 50 cm below the soil surface is 5 oC or higher and have a soil
                                                                                                                                          A
                                      Petronodic Aquicambids        moisture regime that borders on ustic.                                R
                                                                                                                   Ustic Aquicambids      I
GGAE. Other Aquicambids that have both:
                                                                    GGAJ. Other Aquicambids.
  1. A moisture control section that, in normal years, is dry in
                                                                                                                 Typic Aquicambids
  all parts for less than three-fourths of the time (cumulative)
  when the soil temperature at a depth of 50 cm below the
  soil surface is 5 oC or higher and a soil moisture regime that    Haplocambids
  borders on xeric; and                                             Key to Subgroups
  2. Throughout one or more horizons with a total thickness         GGDA. Haplocambids that have both:
  of 18 cm or more within 75 cm of the soil surface, one or
  both of the following:                                               1. A lithic contact within 50 cm of the soil surface; and

     a. More than 35 percent (by volume) fragments coarser             2. A moisture control section that, in normal years, is dry in
     than 2.0 mm, of which more than 66 percent is cinders,            all parts for less than three-fourths of the time (cumulative)
     pumice, and pumicelike fragments; or                              when the soil temperature at a depth of 50 cm below the
                                                                       soil surface is 5 oC or higher and a soil moisture regime that
     b. A fine-earth fraction containing 30 percent or more            borders on xeric.
     particles 0.02 to 2.0 mm in diameter, of which 5 percent                                             Lithic Xeric Haplocambids
     or more is volcanic glass, and [(Al plus 1/2 Fe, percent
     extracted by ammonium oxalate) times 60] plus the              GGDB. Other Haplocambids that have both:
     volcanic glass (percent) is 30 or more.
                                    Vitrixerandic Aquicambids          1. A lithic contact within 50 cm of the soil surface; and
                                                                       2. A moisture control section that, in normal years, is dry in
GGAF. Other Aquicambids that have, throughout one or more
                                                                       all parts for less than three-fourths of the time (cumulative)
horizons with a total thickness of 18 cm or more within 75 cm
                                                                       when the soil temperature at a depth of 50 cm below the
of the soil surface, one or both of the following:
                                                                       soil surface is 5 oC or higher and a soil moisture regime that
  1. More than 35 percent (by volume) fragments coarser                borders on ustic.
  than 2.0 mm, of which more than 66 percent is cinders,                                                   Lithic Ustic Haplocambids
  pumice, and pumicelike fragments; or
                                                                    GGDC. Other Haplocambids that have a lithic contact within
  2. A fine-earth fraction containing 30 percent or more
                                                                    50 cm of the soil surface.
  particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                                                                                        Lithic Haplocambids
  more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
  by ammonium oxalate) times 60] plus the volcanic glass
                                                                    GGDD. Other Haplocambids that have both:
  (percent) is 30 or more.
                                       Vitrandic Aquicambids           1.   One or both of the following:
110                                                                                                        Keys to Soil Taxonomy



       a. Cracks within 125 cm of the soil surface that are 5        2. A moisture control section that, in normal years, is dry in
       mm or more wide through a thickness of 30 cm or more          all parts for less than three-fourths of the time (cumulative)
       for some time in normal years and slickensides or wedge-      when the soil temperature at a depth of 50 cm below the
       shaped peds in a layer 15 cm or more thick that has its       soil surface is 5 oC or higher and a soil moisture regime that
       upper boundary within 125 cm of the soil surface; or          borders on xeric.
                                                                                                    Durinodic Xeric Haplocambids
       b. A linear extensibility of 6.0 cm or more between the
       soil surface and either a depth of 100 cm or a densic,
                                                                   GGDH. Other Haplocambids that have one or more horizons,
       lithic, or paralithic contact if shallower; and
                                                                   within 100 cm of the soil surface and with a combined thickness
  2. A moisture control section that, in normal years, is dry in   of 15 cm or more, that contain 20 percent or more (by volume)
  all parts for less than three-fourths of the time (cumulative)   durinodes or are brittle and have at least a firm rupture-
  when the soil temperature at a depth of 50 cm below the          resistance class when moist.
  soil surface is 5 oC or higher and a soil moisture regime that                                          Durinodic Haplocambids
  borders on xeric.
                                         Xerertic Haplocambids     GGDI. Other Haplocambids that have both:
                                                                     1. One or more horizons, within 100 cm of the soil
GGDE.     Other Haplocambids that have both:
                                                                     surface and with a combined thickness of 15 cm or more,
  1.    One or both of the following:                                that contain 20 percent or more (by volume) nodules or
                                                                     concretions; and
       a. Cracks within 125 cm of the soil surface that are 5
       mm or more wide through a thickness of 30 cm or more          2. A moisture control section that, in normal years, is dry in
       for some time in normal years and slickensides or wedge-      all parts for less than three-fourths of the time (cumulative)
       shaped peds in a layer 15 cm or more thick that has its       when the soil temperature at a depth of 50 cm below the
       upper boundary within 125 cm of the soil surface; or          soil surface is 5 oC or higher and a soil moisture regime that
       b. A linear extensibility of 6.0 cm or more between the       borders on xeric.
       soil surface and either a depth of 100 cm or a densic,                                      Petronodic Xeric Haplocambids
       lithic, or paralithic contact if shallower; and
                                                                   GGDJ.    Other Haplocambids that have both:
  2. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)     1. One or more horizons, within 100 cm of the soil
  when the soil temperature at a depth of 50 cm below the            surface and with a combined thickness of 15 cm or more,
  soil surface is 5 oC or higher and a soil moisture regime that     that contain 20 percent or more (by volume) nodules or
  borders on ustic.                                                  concretions; and
                                          Ustertic Haplocambids      2. A moisture control section that, in normal years, is dry in
                                                                     all parts for less than three-fourths of the time (cumulative)
GGDF. Other Haplocambids that have one or both of the                when the soil temperature at a depth of 50 cm below the
following:                                                           soil surface is 5 oC or higher and a soil moisture regime that
  1. Cracks within 125 cm of the soil surface that are 5 mm          borders on ustic.
  or more wide through a thickness of 30 cm or more for some                                        Petronodic Ustic Haplocambids
  time in normal years and slickensides or wedge-shaped peds
  in a layer 15 cm or more thick that has its upper boundary       GGDK. Other Haplocambids that have one or more horizons,
  within 125 cm of the soil surface; or                            within 100 cm of the soil surface and with a combined thickness
                                                                   of 15 cm or more, that contain 20 percent or more (by volume)
  2. A linear extensibility of 6.0 cm or more between the soil     nodules or concretions.
  surface and either a depth of 100 cm or a densic, lithic, or                                          Petronodic Haplocambids
  paralithic contact, whichever is shallower.
                                          Vertic Haplocambids      GGDL. Other Haplocambids that have both:

GGDG.      Other Haplocambids that have both:                        1. A horizon at least 25 cm thick within 100 cm of the soil
                                                                     surface that has an exchangeable sodium percentage of 15 or
  1. One or more horizons, within 100 cm of the soil surface         more (or an SAR of 13 or more) during at least 1 month in
  and with a combined thickness of 15 cm or more, that               normal years; and
  contain 20 percent or more (by volume) durinodes or are
  brittle and have at least a firm rupture-resistance class when     2. A moisture control section that, in normal years, is dry in
  moist; and                                                         all parts for less than three-fourths of the time (cumulative)
Aridisols	                                                                                                                           111



   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	              more	is	volcanic	glass,	and	[(Al	plus	1/2	Fe,	percent	extracted	
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	       by	ammonium	oxalate)	times	60]	plus	the	volcanic	glass	
   borders	on	xeric.                                                     (percent)	is	30	or	more.
                                      Sodic Xeric Haplocambids                                               Vitrandic Haplocambids

GGDM.	 Other	Haplocambids	that	have	both:                             GGDQ.	 Other	Haplocambids	that:
   1.	 A	horizon	at	least	25	cm	thick	within	100	cm	of	the	soil	         1.	 In	normal	years,	are	dry	in	all	parts	of	the	moisture	
   surface	that	has	an	exchangeable	sodium	percentage	of	15	or	          control	section	for	less	than	three-fourths	of	the	time	
   more	(or	an	SAR	of	13	or	more)	during	at	least	1	month	in	            (cumulative)	when	the	soil	temperature	at	a	depth	of	50	
   normal	years;	and                                                     cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	      moisture	regime	that	borders	on	xeric;	and
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	       2.	 Have	an	irregular	decrease	in	organic-carbon	content	
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	              (Holocene	age)	between	a	depth	of	25	cm	and	either	a	depth	
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	       of	125	cm	below	the	mineral	soil	surface	or	a	densic,	lithic,	
   borders	on	ustic.                                                     or	paralithic	contact,	whichever	is	shallower.
                                       Sodic Ustic Haplocambids                                         Xerofluventic Haplocambids
                                                                                                                                            A
                                                                                                                                            R
GGDN.	 Other	Haplocambids	that	have,	in	a	horizon	at	least	                                                                                 I
                                                                      GGDR.	 Other	Haplocambids	that:
25	cm	thick	within	100	cm	of	the	soil	surface,	an	exchangeable	
sodium	percentage	of	15	or	more	(or	an	SAR	of	13	or	more)	               1.	 In	normal	years,	are	dry	in	all	parts	of	the	moisture	
during	at	least	1	month	in	normal	years.                                 control	section	for	less	than	three-fourths	of	the	time	
                                           Sodic Haplocambids            (cumulative)	when	the	soil	temperature	at	a	depth	of	50	
                                                                         cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
GGDO.	 Other	Haplocambids	that	have	both:                                moisture	regime	that	borders	on	ustic;	and
   1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	      2.	 Have	an	irregular	decrease	in	organic-carbon	content	
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	       (Holocene	age)	between	a	depth	of	25	cm	and	either	a	depth	
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	              of	125	cm	below	the	mineral	soil	surface	or	a	densic,	lithic,	
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	       or	paralithic	contact,	whichever	is	shallower.
   borders	on	xeric;	and                                                                                  Ustifluventic Haplocambids
   2.	 Throughout	one	or	more	horizons	with	a	total	thickness	
   of	18	cm	or	more	within	75	cm	of	the	soil	surface,	one or          GGDS.	 Other	Haplocambids	that	have	an	irregular	decrease	
   both	of	the	following:                                             in	organic-carbon	content	(Holocene	age)	between	a	depth	of	25	
                                                                      cm	and	either	a	depth	of	125	cm	below	the	mineral	soil	surface	
      a.	 More	than	35	percent	(by	volume)	fragments	coarser	         or	a	densic,	lithic,	or	paralithic	contact,	whichever	is	shallower.
      than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	                                                   Fluventic Haplocambids
      pumice,	and	pumicelike	fragments;	or
      b.	 A	fine-earth	fraction	containing	30	percent	or	more	        GGDT.	 Other	Haplocambids	that,	in	normal	years,	are	dry	
      particles	0.02	to	2.0	mm	in	diameter,	of	which	5	percent	       in	all	parts	of	the	moisture	control	section	for	less	than	three-
      or	more	is	volcanic	glass,	and	[(Al	plus	1/2	Fe,	percent	       fourths	of	the	time	(cumulative)	when	the	soil	temperature	at	a	
      extracted	by	ammonium	oxalate)	times	60]	plus	the	              depth	of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	
      volcanic	glass	(percent)	is	30	or	more.                         a	soil	moisture	regime	that	borders	on	xeric.
                                   Vitrixerandic Haplocambids                                                      Xeric Haplocambids

GGDP.	 Other	Haplocambids	that	have,	throughout	one	or	               GGDU.	 Other	Haplocambids	that,	in	normal	years,	are	dry	
more	horizons	with	a	total	thickness	of	18	cm	or	more	within	75	      in	all	parts	of	the	moisture	control	section	for	less	than	three-
cm	of	the	soil	surface,	one or both	of	the	following:                 fourths	of	the	time	(cumulative)	when	the	soil	temperature	at	a	
                                                                      depth	of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	            a	soil	moisture	regime	that	borders	on	ustic.
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	                                                          Ustic Haplocambids
   pumice,	and	pumicelike	fragments;	or
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	           GGDV.	 Other	Haplocambids.
   particles	0.02	to	2.0	mm	in	diameter,	of	which	5	percent	or	                                                   Typic Haplocambids
112                                                                                                           Keys to Soil Taxonomy



Petrocambids                                                         fourths of the time (cumulative) when the soil temperature at a
                                                                     depth of 50 cm below the soil surface is 5 oC or higher and have
Key to Subgroups                                                     a soil moisture regime that borders on ustic.
GGBA. Petrocambids that have, in a horizon at least 25 cm                                                         Ustic Petrocambids
thick within 100 cm of the soil surface, an exchangeable sodium
percentage of 15 or more (or an SAR of 13 or more) during at         GGBF. Other Petrocambids.
least 1 month in normal years.                                                                                  Typic Petrocambids
                                             Sodic Petrocambids

GGBB. Other Petrocambids that have both:                             Cryids
   1. A moisture control section that, in normal years, is dry in    Key to Great Groups
   all parts for less than three-fourths of the time (cumulative)
   when the soil temperature at a depth of 50 cm below the           GAA. Cryids that have a salic horizon within 100 cm of the
   soil surface is 5 oC or higher and a soil moisture regime that    soil surface.
   borders on xeric; and                                                                                        Salicryids, p. 115

   2. Throughout one or more horizons with a total thickness         GAB. Other Cryids that have a duripan or a petrocalcic or
   of 18 cm or more within 75 cm of the soil surface, one or         petrogypsic horizon within 100 cm of the soil surface.
   both of the following:                                                                                        Petrocryids, p. 115
      a. More than 35 percent (by volume) fragments coarser
                                                                     GAC. Other Cryids that have a gypsic horizon within 100 cm
      than 2.0 mm, of which more than 66 percent is cinders,
                                                                     of the soil surface.
      pumice, and pumicelike fragments; or
                                                                                                              Gypsicryids, p. 114
      b. A fine-earth fraction containing 30 percent or more
      particles 0.02 to 2.0 mm in diameter, of which 5 percent       GAD. Other Cryids that have an argillic or natric horizon.
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent                                                   Argicryids, p. 112
      extracted by ammonium oxalate) times 60] plus the
      volcanic glass (percent) is 30 or more.                        GAE. Other Cryids that have a calcic horizon within 100 cm
                                    Vitrixerandic Petrocambids       of the soil surface.
                                                                                                               Calcicryids, p. 113
GGBC. Other Petrocambids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm        GAF. Other Cryids.
of the soil surface, one or both of the following:                                                              Haplocryids, p. 114
   1. More than 35 percent (by volume) fragments coarser
   than 2.0 mm, of which more than 66 percent is cinders,            Argicryids
   pumice, and pumicelike fragments; or                              Key to Subgroups
   2. A fine-earth fraction containing 30 percent or more            GADA. Argicryids that have a lithic contact within 50 cm of
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or       the soil surface.
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted                                               Lithic Argicryids
   by ammonium oxalate) times 60] plus the volcanic glass
   (percent) is 30 or more.                                          GADB. Other Argicryids that have one or both of the
                                        Vitrandic Petrocambids       following:
                                                                       1. Cracks within 125 cm of the soil surface that are 5
GGBD. Other Petrocambids that, in normal years, are dry
                                                                       mm or more wide throughout a thickness of 30 cm or more
in all parts of the moisture control section for less than three-
                                                                       for some time in normal years and slickensides or wedge-
fourths of the time (cumulative) when the soil temperature at a
                                                                       shaped peds in a layer 15 cm or more thick that has its upper
depth of 50 cm below the soil surface is 5 oC or higher and have
                                                                       boundary within 125 cm of the mineral soil surface; or
a soil moisture regime that borders on xeric.
                                              Xeric Petrocambids       2. A linear extensibility of 6.0 cm or more between the
                                                                       mineral soil surface and either a depth of 100 cm or a densic,
GGBE. Other Petrocambids that, in normal years, are dry                lithic, or paralithic contact, whichever is shallower.
in all parts of the moisture control section for less than three-                                                    Vertic Argicryids
Aridisols                                                                                                                          113



GADC. Other Argicryids that have a natric horizon within 100         Calcicryids
cm of the soil surface.
                                          Natric Argicryids          Key to Subgroups
                                                                     GAEA. Calcicryids that have a lithic contact within 50 cm of
GADD.       Other Argicryids that have both:                         the soil surface.
   1. A moisture control section that, in normal years, is dry in                                               Lithic Calcicryids
   all parts for less than three-fourths of the time (cumulative)
   when the soil temperature at a depth of 50 cm below the           GAEB. Other Calcicryids that have both:
   soil surface is 5 oC or higher and a soil moisture regime that       1. A moisture control section that, in normal years, is dry in
   borders on xeric; and                                                all parts for less than three-fourths of the time (cumulative)
   2. Throughout one or more horizons with a total thickness            when the soil temperature at a depth of 50 cm below the
   of 18 cm or more within 75 cm of the soil surface, one or            soil surface is 5 oC or higher and a soil moisture regime that
   both of the following:                                               borders on xeric; and

      a. More than 35 percent (by volume) fragments coarser             2. Throughout one or more horizons with a total thickness
      than 2.0 mm, of which more than 66 percent is cinders,            of 18 cm or more within 75 cm of the soil surface, one or
      pumice, and pumicelike fragments; or                              both of the following:
                                                                                                                                          A
                                                                           a. More than 35 percent (by volume) fragments coarser          R
      b. A fine-earth fraction containing 30 percent or more                                                                              I
                                                                           than 2.0 mm, of which more than 66 percent is cinders,
      particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                                                           pumice, and pumicelike fragments; or
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent
      extracted by ammonium oxalate) times 60] plus the                    b. A fine-earth fraction containing 30 percent or more
      volcanic glass (percent) is 30 or more.                              particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                        Vitrixerandic Argicryids           or more is volcanic glass, and [(Al plus 1/2 Fe, percent
                                                                           extracted by ammonium oxalate) times 60] plus the
GADE. Other Argicryids that have, throughout one or more                   volcanic glass (percent) is 30 or more.
horizons with a total thickness of 18 cm or more within 75 cm                                               Vitrixerandic Calcicryids
of the soil surface, one or both of the following:
                                                                     GAEC. Other Calcicryids that have, throughout one or more
   1. More than 35 percent (by volume) fragments coarser
                                                                     horizons with a total thickness of 18 cm or more within 75 cm
   than 2.0 mm, of which more than 66 percent is cinders,
                                                                     of the soil surface, one or both of the following:
   pumice, and pumicelike fragments; or
                                                                        1. More than 35 percent (by volume) fragments coarser
   2. A fine-earth fraction containing 30 percent or more
                                                                        than 2.0 mm, of which more than 66 percent is cinders,
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                                                        pumice, and pumicelike fragments; or
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
   by ammonium oxalate) times 60] plus the volcanic glass               2. A fine-earth fraction containing 30 percent or more
   (percent) is 30 or more.                                             particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                            Vitrandic Argicryids        more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
                                                                        by ammonium oxalate) times 60] plus the volcanic glass
GADF. Other Argicryids that, in normal years, are dry in all            (percent) is 30 or more.
parts of the moisture control section for less than three-fourths                                               Vitrandic Calcicryids
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the soil surface is 5 oC or higher and have a soil    GAED. Other Calcicryids that, in normal years, are dry in all
moisture regime that borders on xeric.                               parts of the moisture control section for less than three-fourths
                                                 Xeric Argicryids    of the time (cumulative) when the soil temperature at a depth
                                                                     of 50 cm below the soil surface is 5 oC or higher and have a soil
GADG. Other Argicryids that, in normal years, are dry in all         moisture regime that borders on xeric.
parts of the moisture control section for less than three-fourths                                                     Xeric Calcicryids
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the soil surface is 5 oC or higher and have a soil    GAEE. Other Calcicryids that, in normal years, are dry in all
moisture regime that borders on ustic.                               parts of the moisture control section for less than three-fourths
                                                  Ustic Argicryids   of the time (cumulative) when the soil temperature at a depth
                                                                     of 50 cm below the soil surface is 5 oC or higher and have a soil
GADH.       Other Argicryids.                                        moisture regime that borders on ustic.
                                               Typic Argicryids                                                       Ustic Calcicryids
114                                                                                                           Keys to Soil Taxonomy



GAEF.    Other Calcicryids.                                         GAFB. Other Haplocryids that have one or both of the
                                             Typic Calcicryids      following:

Gypsicryids                                                            1. Cracks within 125 cm of the soil surface that are 5
                                                                       mm or more wide throughout a thickness of 30 cm or more
Key to Subgroups                                                       for some time in normal years and slickensides or wedge-
GACA.     Gypsicryids that have a calcic horizon.                      shaped peds in a layer 15 cm or more thick that has its upper
                                             Calcic Gypsicryids        boundary within 125 cm of the mineral soil surface; or
                                                                       2. A linear extensibility of 6.0 cm or more between the
GACB. Other Gypsicryids that have both:                                mineral soil surface and either a depth of 100 cm or a densic,
  1. A moisture control section that, in normal years, is dry in       lithic, or paralithic contact, whichever is shallower.
  all parts for less than three-fourths of the time (cumulative)                                                    Vertic Haplocryids
  when the soil temperature at a depth of 50 cm below the
  soil surface is 5 oC or higher and a soil moisture regime that    GAFC.    Other Haplocryids that have both:
  borders on xeric; and                                                1. A moisture control section that, in normal years, is dry in
                                                                       all parts for less than three-fourths of the time (cumulative)
  2. Throughout one or more horizons with a total thickness
                                                                       when the soil temperature at a depth of 50 cm below the
  of 18 cm or more within 75 cm of the soil surface, one or
                                                                       soil surface is 5 oC or higher and a soil moisture regime that
  both of the following:
                                                                       borders on xeric; and
      a. More than 35 percent (by volume) fragments coarser
                                                                       2. Throughout one or more horizons with a total thickness
      than 2.0 mm, of which more than 66 percent is cinders,
                                                                       of 18 cm or more within 75 cm of the soil surface, one or
      pumice, and pumicelike fragments; or
                                                                       both of the following:
      b. A fine-earth fraction containing 30 percent or more              a. More than 35 percent (by volume) fragments coarser
      particles 0.02 to 2.0 mm in diameter, of which 5 percent            than 2.0 mm, of which more than 66 percent is cinders,
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent            pumice, and pumicelike fragments; or
      extracted by ammonium oxalate) times 60] plus the
      volcanic glass (percent) is 30 or more.                             b. A fine-earth fraction containing 30 percent or more
                                      Vitrixerandic Gypsicryids           particles 0.02 to 2.0 mm in diameter, of which 5 percent
                                                                          or more is volcanic glass, and [(Al plus 1/2 Fe, percent
                                                                          extracted by ammonium oxalate) times 60] plus the
GACC. Other Gypsicryids that have, throughout one or more                 volcanic glass (percent) is 30 or more.
horizons with a total thickness of 18 cm or more within 75 cm                                             Vitrixerandic Haplocryids
of the soil surface, one or both of the following:
  1. More than 35 percent (by volume) fragments coarser             GAFD. Other Haplocryids that have, throughout one or more
  than 2.0 mm, of which more than 66 percent is cinders,            horizons with a total thickness of 18 cm or more within 75 cm
  pumice, and pumicelike fragments; or                              of the soil surface, one or both of the following:

  2. A fine-earth fraction containing 30 percent or more               1. More than 35 percent (by volume) fragments coarser
  particles 0.02 to 2.0 mm in diameter, of which 5 percent or          than 2.0 mm, of which more than 66 percent is cinders,
  more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted      pumice, and pumicelike fragments; or
  by ammonium oxalate) times 60] plus the volcanic glass               2. A fine-earth fraction containing 30 percent or more
  (percent) is 30 or more.                                             particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                         Vitrandic Gypsicryids         more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
                                                                       by ammonium oxalate) times 60] plus the volcanic glass
GACD.    Other Gypsicryids.                                            (percent) is 30 or more.
                                             Typic Gypsicryids                                                Vitrandic Haplocryids

Haplocryids                                                         GAFE. Other Haplocryids that, in normal years, are dry in all
                                                                    parts of the moisture control section for less than three-fourths
Key to Subgroups
                                                                    of the time (cumulative) when the soil temperature at a depth
GAFA. Haplocryids that have a lithic contact within 50 cm of        of 50 cm below the soil surface is 5 oC or higher and have a soil
the soil surface.                                                   moisture regime that borders on xeric.
                                         Lithic Haplocryids                                                         Xeric Haplocryids
Aridisols	                                                                                                                          115



GAFF.	 Other	Haplocryids	that,	in	normal	years,	are	dry	in	all	       of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
parts	of	the	moisture	control	section	for	less	than	three-fourths	    moisture	regime	that	borders	on	ustic.
of	the	time	(cumulative)	when	the	soil	temperature	at	a	depth	                                                       Ustic Petrocryids
of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
moisture	regime	that	borders	on	ustic.                                GABG.	 Other	Petrocryids.
                                                Ustic Haplocryids                                                   Typic Petrocryids

GAFG.	 Other	Haplocryids.                                             Salicryids
                                              Typic Haplocryids
                                                                      Key to Subgroups
Petrocryids                                                           GAAA.	 Salicryids	that	are	saturated	with	water	in	one	or	more	
                                                                      layers	within	100	cm	of	the	soil	surface	for	1	month	or	more	in	
Key to Subgroups
                                                                      normal	years.
GABA.	 Petrocryids	that	have	both:                                                                                    Aquic Salicryids
   1.	 A	duripan	that	is	strongly	cemented	or	less	cemented	in	
                                                                      GAAB.	 Other	Salicryids.
   all	subhorizons	within	100	cm	of	the	soil	surface;	and
                                                                                                                      Typic Salicryids
                                                                                                                                           A
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	                                                                        R
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	                                                                         I
                                                                      Durids
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	
   borders	on	xeric.                                                  Key to Great Groups
                                              Xereptic Petrocryids    GCA.	 Durids	that	have	a	natric	horizon	above	the	duripan.
                                                                                                                Natridurids,	p.	117
GABB.	 Other	Petrocryids	that	have	both:
   1.	 A	duripan	within	100	cm	of	the	soil	surface;	and               GCB.	 Other	Durids	that	have	an	argillic	horizon	above	the	
                                                                      duripan.
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	                                               Argidurids,	p.	115
   all	parts	for	less	than	three-fourths	of	the	time	(cumulative)	
   when	the	soil	temperature	at	a	depth	of	50	cm	below	the	           GCC.	 Other	Durids.
   soil	surface	is	5	oC	or	higher	and	a	soil	moisture	regime	that	                                                Haplodurids,	p.	116
   borders	on	xeric.
                                          Duric Xeric Petrocryids     Argidurids
GABC.	 Other	Petrocryids	that	have	a	duripan	within	100	cm	           Key to Subgroups
of	the	soil	surface.                                                  GCBA.	 Argidurids	that	have	one or both	of	the	following:
                                          Duric Petrocryids
                                                                         1.	 Cracks	between	the	soil	surface	and	the	top	of	the	
GABD.	 Other	Petrocryids	that	have	a	petrogypsic	horizon	                duripan	that	are	5	mm	or	more	wide	through	a	thickness	
within	100	cm	of	the	soil	surface.                                       of	30	cm	or	more	for	some	time	in	normal	years	and	
                                    Petrogypsic Petrocryids              slickensides	or	wedge-shaped	peds	in	a	layer	15	cm	or	more	
                                                                         thick	that	is	above	the	duripan;	or
GABE.	 Other	Petrocryids	that,	in	normal	years,	are	dry	in	all	          2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	soil	
parts	of	the	moisture	control	section	for	less	than	three-fourths	       surface	and	the	top	of	the	duripan.
of	the	time	(cumulative)	when	the	soil	temperature	at	a	depth	                                                      Vertic Argidurids
of	50	cm	below	the	soil	surface	is	5	oC	or	higher	and	have	a	soil	
moisture	regime	that	borders	on	xeric.
                                                                      GCBB.	 Other	Argidurids	that	are	either:
                                                Xeric Petrocryids
                                                                         1.	 Irrigated	and	have	aquic	conditions	for	some	time	in	
GABF.	 Other	Petrocryids	that,	in	normal	years,	are	dry	in	all	          normal	years	in	one	or	more	layers	within	100	cm	of	the	soil	
parts	of	the	moisture	control	section	for	less	than	three-fourths	       surface;	or
of	the	time	(cumulative)	when	the	soil	temperature	at	a	depth	
116                                                                                                              Keys to Soil Taxonomy



   2. Saturated with water in one or more layers within 100               when the soil temperature at a depth of 50 cm below the
   cm of the soil surface for 1 month or more in normal years.            soil surface is 5 oC or higher and a soil moisture regime that
                                              Aquic Argidurids            borders on xeric; and
                                                                          2. Throughout one or more horizons with a total thickness
GCBC. Other Argidurids that have both:                                    of 18 cm or more within 75 cm of the soil surface, one or
   1. An argillic horizon that has 35 percent or more clay in             both of the following:
   the fine-earth fraction of some part; and either                          a. More than 35 percent (by volume) fragments coarser
      a. A clay increase of 15 percent or more (absolute)                    than 2.0 mm, of which more than 66 percent is cinders,
      within a vertical distance of 2.5 cm either within the                 pumice, and pumicelike fragments; or
      argillic horizon or at its upper boundary; or                          b. A fine-earth fraction containing 30 percent or more
      b. If there is an Ap horizon directly above the argillic               particles 0.02 to 2.0 mm in diameter, of which 5 percent
      horizon, a clay increase of 10 percent or more (absolute)              or more is volcanic glass, and [(Al plus 1/2 Fe, percent
      at the upper boundary of the argillic horizon; and                     extracted by ammonium oxalate) times 60] plus the
                                                                             volcanic glass (percent) is 30 or more.
   2. A moisture control section that, in normal years, is dry in                                             Vitrixerandic Argidurids
   all parts for less than three-fourths of the time (cumulative)
   when the soil temperature at a depth of 50 cm below the
                                                                       GCBH. Other Argidurids that have, throughout one or more
   soil surface is 5 oC or higher and a soil moisture regime that      horizons with a total thickness of 18 cm or more within 75 cm
   borders on xeric.                                                   of the soil surface, one or both of the following:
                                       Abruptic Xeric Argidurids
                                                                          1. More than 35 percent (by volume) fragments coarser
GCBD. Other Argidurids that have an argillic horizon that has             than 2.0 mm, of which more than 66 percent is cinders,
35 percent or more clay in the fine-earth fraction of some part;          pumice, and pumicelike fragments; or
and either                                                                2. A fine-earth fraction containing 30 percent or more
   1. A clay increase of 15 percent or more (absolute) within a           particles 0.02 to 2.0 mm in diameter, of which 5 percent or
   vertical distance of 2.5 cm within the argillic horizon or at its      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
   upper boundary; or                                                     by ammonium oxalate) times 60] plus the volcanic glass
                                                                          (percent) is 30 or more.
   2. If there is an Ap horizon directly above the argillic                                                        Vitrandic Argidurids
   horizon, a clay increase of 10 percent or more (absolute) at
   the upper boundary of the argillic horizon.                         GCBI. Other Argidurids that, in normal years, are dry in all
                                           Abruptic Argidurids         parts of the moisture control section for less than three-fourths
                                                                       of the time (cumulative) when the soil temperature at a depth
GCBE. Other Argidurids that have both:                                 of 50 cm below the soil surface is 5 oC or higher and have a soil
   1. A duripan that is strongly cemented or less cemented in          moisture regime that borders on xeric.
   all subhorizons; and                                                                                                 Xeric Argidurids

   2. A moisture control section that, in normal years, is dry in      GCBJ. Other Argidurids that, in normal years, are dry in all
   all parts for less than three-fourths of the time (cumulative)      parts of the moisture control section for less than three-fourths
   when the soil temperature at a depth of 50 cm below the             of the time (cumulative) when the soil temperature at a depth
   soil surface is 5 oC or higher and a soil moisture regime that      of 50 cm below the soil surface is 5 oC or higher and have a soil
   borders on xeric.                                                   moisture regime that borders on ustic.
                                         Haploxeralfic Argidurids                                                       Ustic Argidurids

GCBF. Other Argidurids that have a duripan that is strongly            GCBK. Other Argidurids.
cemented or less cemented in all subhorizons.                                                                         Typic Argidurids
                                           Argidic Argidurids
                                                                       Haplodurids
GCBG.     Other Argidurids that have both:
                                                                       Key to Subgroups
   1. A moisture control section that, in normal years, is dry in
   all parts for less than three-fourths of the time (cumulative)      GCCA. Haplodurids that meet both of the following:
Aridisols                                                                                                                        117



  1. Have a duripan that is strongly cemented or less                    extracted by ammonium oxalate) times 60] plus the
  cemented in all subhorizons; and                                       volcanic glass (percent) is 30 or more.
                                                                                                        Vitrixerandic Haplodurids
  2. Are either:
     a. Irrigated and have aquic conditions for some time in       GCCF. Other Haplodurids that have, throughout one or more
     normal years in one or more layers within 100 cm of the       horizons with a total thickness of 18 cm or more within 75 cm
     soil surface; or                                              of the soil surface, one or both of the following:
     b. Saturated with water in one or more layers within             1. More than 35 percent (by volume) fragments coarser
     100 cm of the soil surface for 1 month or more in normal         than 2.0 mm, of which more than 66 percent is cinders,
     years.                                                           pumice, and pumicelike fragments; or
                                   Aquicambidic Haplodurids
                                                                      2. A fine-earth fraction containing 30 percent or more
                                                                      particles 0.02 to 2.0 mm in diameter, of which 5 percent or
GCCB. Other Haplodurids that are either:
                                                                      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
  1. Irrigated and have aquic conditions for some time in             by ammonium oxalate) times 60] plus the volcanic glass
  normal years in one or more layers within 100 cm of the soil        (percent) is 30 or more.
  surface; or                                                                                               Vitrandic Haplodurids
                                                                                                                                        A
                                                                                                                                        R
  2. Saturated with water in one or more layers within 100         GCCG. Other Haplodurids that have a mean annual soil                 I
  cm of the soil surface for 1 month or more in normal years.      temperature lower than 22 oC, a difference of 5 oC or more
                                           Aquic Haplodurids       between mean summer and mean winter soil temperatures at
                                                                   a depth of 50 cm, and a soil moisture regime that borders on
GCCC.       Other Haplodurids that have both:                      xeric.
  1. A duripan that is strongly cemented or less cemented in                                                    Xeric Haplodurids
  all subhorizons; and
                                                                   GCCH. Other Haplodurids that, in normal years, are dry in all
  2. A mean annual soil temperature lower than 22 oC, a            parts of the moisture control section for less than three-fourths
  difference of 5 oC or more between mean summer and mean          of the time (cumulative) when the soil temperature at a depth
  winter soil temperatures at a depth of 50 cm, and a soil         of 50 cm below the soil surface is 5 oC or higher and have a soil
  moisture regime that borders on xeric.                           moisture regime that borders on ustic.
                                         Xereptic Haplodurids                                                      Ustic Haplodurids

GCCD. Other Haplodurids that have a duripan that is strongly       GCCI. Other Haplodurids.
cemented or less cemented in all subhorizons.                                                                   Typic Haplodurids
                                       Cambidic Haplodurids
                                                                   Natridurids
GCCE.       Other Haplodurids that have both:
                                                                   Key to Subgroups
  1. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)   GCAA. Natridurids that have one or both of the following:
  when the soil temperature at a depth of 50 cm below the
                                                                      1. Cracks between the soil surface and the top of the
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                      duripan that are 5 mm or more wide through a thickness
  borders on xeric; and
                                                                      of 30 cm or more for some time in normal years and
  2. Throughout one or more horizons with a total thickness           slickensides or wedge-shaped peds in a layer 15 cm
  of 18 cm or more within 75 cm of the soil surface, one or           or more thick that is above the duripan; or
  both of the following:
                                                                      2. A linear extensibility of 6.0 cm or more between the soil
     a. More than 35 percent (by volume) fragments coarser            surface and the top of the duripan.
     than 2.0 mm, of which more than 66 percent is cinders,                                                    Vertic Natridurids
     pumice, and pumicelike fragments; or
                                                                   GCAB. Other Natridurids that meet both of the following:
     b. A fine-earth fraction containing 30 percent or more
     particles 0.02 to 2.0 mm in diameter, of which 5 percent         1. Have a duripan that is strongly cemented or less
     or more is volcanic glass, and [(Al plus 1/2 Fe, percent         cemented in all subhorizons; and
118                                                                                                          Keys to Soil Taxonomy



  2. Are either:                                                   GCAG. Other Natridurids that have, throughout one or more
                                                                   horizons with a total thickness of 18 cm or more within 75 cm
      a. Irrigated and have aquic conditions for some time in
                                                                   of the soil surface, one or both of the following:
      normal years in one or more layers within 100 cm of the
      soil surface; or                                                1. More than 35 percent (by volume) fragments coarser
                                                                      than 2.0 mm, of which more than 66 percent is cinders,
      b. Saturated with water in one or more layers within
                                                                      pumice, and pumicelike fragments; or
      100 cm of the soil surface for 1 month or more in normal
      years.                                                          2. A fine-earth fraction containing 30 percent or more
                                Aquic Natrargidic Natridurids         particles 0.02 to 2.0 mm in diameter, of which 5 percent or
                                                                      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
GCAC.    Other Natridurids that are either:                           by ammonium oxalate) times 60] plus the volcanic glass
                                                                      (percent) is 30 or more.
  1. Irrigated and have aquic conditions for some time in
                                                                                                             Vitrandic Natridurids
  normal years in one or more layers within 100 cm of the soil
  surface; or                                                      GCAH. Other Natridurids that, in normal years, are dry in all
  2. Saturated with water in one or more layers within 100         parts of the moisture control section for less than three-fourths
  cm of the soil surface for 1 month or more in normal years.      of the time (cumulative) when the soil temperature at a depth
                                           Aquic Natridurids       of 50 cm below the soil surface is 5 oC or higher and have a soil
                                                                   moisture regime that borders on xeric.
GCAD.    Other Natridurids that have both:                                                                         Xeric Natridurids
  1. A duripan that is strongly cemented or less cemented in       GCAI. Other Natridurids.
  all subhorizons; and                                                                                           Typic Natridurids
  2. A moisture control section that, in normal years, is dry in
  all parts for less than three-fourths of the time (cumulative)   Gypsids
  when the soil temperature at a depth of 50 cm below the
  soil surface is 5 oC or higher and a soil moisture regime that   Key to Great Groups
  borders on xeric.
                                       Natrixeralfic Natridurids   GDA. Gypsids that have a petrogypsic or petrocalcic horizon
                                                                   within 100 cm of the soil surface.
GCAE. Other Natridurids that have a duripan that is strongly                                               Petrogypsids, p. 121
cemented or less cemented in all subhorizons.
                                      Natrargidic Natridurids      GDB. Other Gypsids that have a natric horizon within 100 cm
                                                                   of the soil surface.
GCAF.    Other Natridurids that have both:                                                                 Natrigypsids, p. 121
  1. A moisture control section that, in normal years, is dry in   GDC. Other Gypsids that have an argillic horizon within 100
  all parts for less than three-fourths of the time (cumulative)   cm of the soil surface.
  when the soil temperature at a depth of 50 cm below the                                                   Argigypsids, p. 118
  soil surface is 5 oC or higher and a soil moisture regime that
  borders on xeric; and                                            GDD. Other Gypsids that have a calcic horizon within 100 cm
  2. Throughout one or more horizons with a total thickness        of the soil surface.
  of 18 cm or more within 75 cm of the soil surface, one or                                                Calcigypsids, p. 119
  both of the following:
                                                                   GDE. Other Gypsids.
      a. More than 35 percent (by volume) fragments coarser                                                   Haplogypsids, p. 120
      than 2.0 mm, of which more than 66 percent is cinders,
      pumice, and pumicelike fragments; or
                                                                   Argigypsids
      b. A fine-earth fraction containing 30 percent or more
                                                                   Key to Subgroups
      particles 0.02 to 2.0 mm in diameter, of which 5 percent
      or more is volcanic glass, and [(Al plus 1/2 Fe, percent     GDCA. Argigypsids that have a lithic contact within 50 cm of
      extracted by ammonium oxalate) times 60] plus the            the soil surface.
      volcanic glass (percent) is 30 or more.                                                                Lithic Argigypsids
                                      Vitrixerandic Natridurids
Aridisols                                                                                                                        119



GDCB. Other Argigypsids that have one or both of the                   by ammonium oxalate) times 60] plus the volcanic glass
following:                                                             (percent) is 30 percent or more.
                                                                                                          Vitrandic Argigypsids
  1. Cracks within 125 cm of the soil surface that are 5 mm
  or more wide through a thickness of 30 cm or more for some        GDCG. Other Argigypsids that, in normal years, are dry in all
  time in normal years and slickensides or wedge-shaped peds        parts of the moisture control section for less than three-fourths
  in a layer 15 cm or more thick that has its upper boundary        of the time (cumulative) when the soil temperature at a depth
  within 125 cm of the soil surface; or                             of 50 cm below the soil surface is 5 oC or higher and have a soil
  2. A linear extensibility of 6.0 cm or more between the soil      moisture regime that borders on xeric.
  surface and either a depth of 100 cm or a densic, lithic, or                                                      Xeric Argigypsids
  paralithic contact, whichever is shallower.
                                              Vertic Argigypsids    GDCH. Other Argigypsids that, in normal years, are dry in all
                                                                    parts of the moisture control section for less than three-fourths
GDCC. Other Argigypsids that have a calcic horizon overlying        of the time (cumulative) when the soil temperature at a depth
the gypsic horizon.                                                 of 50 cm below the soil surface is 5 oC or higher and have a soil
                                        Calcic Argigypsids          moisture regime that borders on ustic.
                                                                                                                    Ustic Argigypsids
                                                                                                                                        A
GDCD. Other Argigypsids that have one or more horizons,                                                                                 R
within 100 cm of the soil surface and with a combined thickness     GDCI. Other Argigypsids.                                            I
of 15 cm or more, that contain 20 percent or more (by volume)                                                    Typic Argigypsids
durinodes, nodules, or concretions.                                 Calcigypsids
                                       Petronodic Argigypsids
                                                                    Key to Subgroups
GDCE.       Other Argigypsids that have both:                       GDDA. Calcigypsids that have a lithic contact within 50 cm
  1. A moisture control section that, in normal years, is dry in    of the soil surface.
  all parts for less than three-fourths of the time (cumulative)                                             Lithic Calcigypsids
  when the soil temperature at a depth of 50 cm below the
                                                                    GDDB. Other Calcigypsids that have one or more horizons,
  soil surface is 5 oC or higher and a soil moisture regime that
                                                                    within 100 cm of the soil surface and with a combined thickness
  borders on xeric; and
                                                                    of 15 cm or more, that contain 20 percent or more (by volume)
  2. Throughout one or more horizons with a total thickness         durinodes, nodules, or concretions.
  of 18 cm or more within 75 cm of the soil surface, one or                                                Petronodic Calcigypsids
  both of the following:
                                                                    GDDC. Other Calcigypsids that have both:
     a. More than 35 percent (by volume) fragments coarser
     than 2.0 mm, of which more than 66 percent is cinders,            1. A moisture control section that, in normal years, is dry in
     pumice, and pumicelike fragments; or                              all parts for less than three-fourths of the time (cumulative)
     b. A fine-earth fraction containing 30 percent or more            when the soil temperature at a depth of 50 cm below the
     particles 0.02 to 2.0 mm in diameter, of which 5 percent          soil surface is 5 oC or higher and a soil moisture regime that
     or more is volcanic glass, and [(Al plus 1/2 Fe, percent          borders on xeric; and
     extracted by ammonium oxalate) times 60] plus the                 2. Throughout one or more horizons with a total thickness
     volcanic glass (percent) is 30 or more.                           of 18 cm or more within 75 cm of the soil surface, one or
                                     Vitrixerandic Argigypsids         both of the following:
GDCF. Other Argigypsids that have, throughout one or more                 a. More than 35 percent (by volume) fragments coarser
horizons with a total thickness of 18 cm or more within 75 cm             than 2.0 mm, of which more than 66 percent is cinders,
of the soil surface, one or both of the following:                        pumice, and pumicelike fragments; or
  1. More than 35 percent (by volume) fragments coarser                   b. A fine-earth fraction containing 30 percent or more
  than 2.0 mm, of which more than 66 percent is cinders,                  particles 0.02 to 2.0 mm in diameter, of which 5 percent
  pumice, and pumicelike fragments; or                                    or more is volcanic glass, and [(Al plus 1/2 Fe, percent
  2. A fine-earth fraction containing 30 percent or more                  extracted by ammonium oxalate) times 60] plus the
  particles 0.02 to 2.0 mm in diameter, of which 5 percent or             volcanic glass (percent) is 30 or more.
  more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted                                        Vitrixerandic Calcigypsids
120                                                                                                            Keys to Soil Taxonomy



GDDD. Other Calcigypsids that have, throughout one or more           GDEE.    Other Haplogypsids that have both:
horizons with a total thickness of 18 cm or more within 75 cm
                                                                        1. A moisture control section that, in normal years, is dry in
of the soil surface, one or both of the following:
                                                                        all parts for less than three-fourths of the time (cumulative)
   1. More than 35 percent (by volume) fragments coarser                when the soil temperature at a depth of 50 cm below the
   than 2.0 mm, of which more than 66 percent is cinders,               soil surface is 5 oC or higher and a soil moisture regime that
   pumice, and pumicelike fragments; or                                 borders on xeric; and
   2. A fine-earth fraction containing 30 percent or more               2. Throughout one or more horizons with a total thickness
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or          of 18 cm or more within 75 cm of the soil surface, one or
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted      both of the following:
   by ammonium oxalate) times 60] plus the volcanic glass
   (percent) is 30 or more.                                                a. More than 35 percent (by volume) fragments coarser
                                         Vitrandic Calcigypsids            than 2.0 mm, of which more than 66 percent is cinders,
                                                                           pumice, and pumicelike fragments; or
GDDE. Other Calcigypsids that, in normal years, are dry in all
                                                                           b. A fine-earth fraction containing 30 percent or more
parts of the moisture control section for less than three-fourths
                                                                           particles 0.02 to 2.0 mm in diameter, of which 5 percent
of the time (cumulative) when the soil temperature at a depth
                                                                           or more is volcanic glass, and [(Al plus 1/2 Fe, percent
of 50 cm below the soil surface is 5 oC or higher and have a soil
                                                                           extracted by ammonium oxalate) times 60] plus the
moisture regime that borders on xeric.
                                                                           volcanic glass (percent) is 30 or more.
                                               Xeric Calcigypsids
                                                                                                         Vitrixerandic Haplogypsids
GDDF. Other Calcigypsids that, in normal years, are dry in all
parts of the moisture control section for less than three-fourths    GDEF. Other Haplogypsids that have, throughout one or more
of the time (cumulative) when the soil temperature at a depth        horizons with a total thickness of 18 cm or more within 75 cm
of 50 cm below the soil surface is 5 oC or higher and have a soil    0f the soil surface, one or both of the following:
moisture regime that borders on ustic.                                  1. More than 35 percent (by volume) fragments coarser
                                                Ustic Calcigypsids      than 2.0 mm, of which more than 66 percent is cinders,
                                                                        pumice, and pumicelike fragments; or
GDDG.     Other Calcigypsids.
                                             Typic Calcigypsids         2. A fine-earth fraction containing 30 percent or more
                                                                        particles 0.02 to 2.0 mm in diameter, of which 5 percent or
Haplogypsids                                                            more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
                                                                        by ammonium oxalate) times 60] plus the volcanic glass
Key to Subgroups                                                        (percent) is 30 or more.
GDEA. Haplogypsids that have a lithic contact within 50 cm                                                   Vitrandic Haplogypsids
of the soil surface.
                                       Lithic Haplogypsids           GDEG. Other Haplogypsids that, in normal years, are dry
                                                                     in all parts of the moisture control section for less than three-
GDEB. Other Haplogypsids that have a gypsic horizon within           fourths of the time (cumulative) when the soil temperature at a
18 cm of the soil surface.                                           depth of 50 cm below the soil surface is 5 oC or higher and have
                                      Leptic Haplogypsids            a soil moisture regime that borders on xeric.
                                                                                                                   Xeric Haplogypsids
GDEC. Other Haplogypsids that have, in a horizon at least
25 cm thick within 100 cm of the mineral soil surface, an            GDEH. Other Haplogypsids that, in normal years, are dry
exchangeable sodium percentage of 15 or more (or an SAR of           in all parts of the moisture control section for less than three-
13 or more) during at least 1 month in normal years.                 fourths of the time (cumulative) when the soil temperature at a
                                           Sodic Haplogypsids        depth of 50 cm below the soil surface is 5 oC or higher and have
                                                                     a soil moisture regime that borders on ustic.
GDED. Other Haplogypsids that have one or more horizons,                                                            Ustic Haplogypsids
within 100 cm of the soil surface and with a combined thickness
of 15 cm or more, that contain 20 percent or more (by volume)        GDEI. Other Haplogypsids.
durinodes, nodules, or concretions.                                                                              Typic Haplogypsids
                                      Petronodic Haplogypsids
Aridisols                                                                                                                        121



Natrigypsids                                                          2. A fine-earth fraction containing 30 percent or more
                                                                      particles 0.02 to 2.0 mm in diameter, of which 5 percent or
Key to Subgroups                                                      more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
GDBA. Natrigypsids that have a lithic contact within 50 cm of         by ammonium oxalate) times 60] plus the volcanic glass
the soil surface.                                                     (percent) is 30 or more.
                                         Lithic Natrigypsids                                                Vitrandic Natrigypsids

GDBB. Other Natrigypsids that have one or both of the              GDBF. Other Natrigypsids that, in normal years, are dry in all
following:                                                         parts of the moisture control section for less than three-fourths
                                                                   of the time (cumulative) when the soil temperature at a depth
  1. Cracks within 125 cm of the soil surface that are 5 mm
                                                                   of 50 cm below the soil surface is 5 oC or higher and have a soil
  or more wide through a thickness of 30 cm or more for some
                                                                   moisture regime that borders on xeric.
  time in normal years and slickensides or wedge-shaped peds
                                                                                                                  Xeric Natrigypsids
  in a layer 15 cm or more thick that has its upper boundary
  within 125 cm of the soil surface; or
                                                                   GDBG. Other Natrigypsids that, in normal years, are dry in all
  2. A linear extensibility of 6.0 cm or more between the soil     parts of the moisture control section for less than three-fourths
  surface and either a depth of 100 cm or a densic, lithic, or     of the time (cumulative) when the soil temperature at a depth
                                                                                                                                        A
  paralithic contact, whichever is shallower.                      of 50 cm below the soil surface is 5 oC or higher and have a soil    R
                                            Vertic Natrigypsids    moisture regime that borders on ustic.                               I
                                                                                                                  Ustic Natrigypsids
GDBC. Other Natrigypsids that have one or more horizons,
within 100 cm of the soil surface and with a combined thickness    GDBH. Other Natrigypsids.
of 15 cm or more, that contain 20 percent or more (by volume)                                                   Typic Natrigypsids
durinodes, nodules, or concretions.
                                      Petronodic Natrigypsids      Petrogypsids
GDBD.       Other Natrigypsids that have both:                     Key to Subgroups

  1. A moisture control section that, in normal years, is dry in   GDAA. Petrogypsids that have a petrocalcic horizon within
  all parts for less than three-fourths of the time (cumulative)   100 cm of the soil surface.
  when the soil temperature at a depth of 50 cm below the                                             Petrocalcic Petrogypsids
  soil surface is 5 oC or higher and a soil moisture regime that
  borders on xeric; and                                            GDAB. Other Petrogypsids that have a calcic horizon
                                                                   overlying the petrogypsic horizon.
  2. Throughout one or more horizons with a total thickness                                               Calcic Petrogypsids
  of 18 cm or more within 75 cm of the soil surface, one or
  both of the following:                                           GDAC. Other Petrogypsids that have both:
     a. More than 35 percent (by volume) fragments coarser            1. A moisture control section that, in normal years, is dry in
     than 2.0 mm, of which more than 66 percent is cinders,           all parts for less than three-fourths of the time (cumulative)
     pumice, and pumicelike fragments; or                             when the soil temperature at a depth of 50 cm below the
     b. A fine-earth fraction containing 30 percent or more           soil surface is 5 oC or higher and a soil moisture regime that
     particles 0.02 to 2.0 mm in diameter, of which 5 percent         borders on xeric; and
     or more is volcanic glass, and [(Al plus 1/2 Fe, percent         2. Throughout one or more horizons with a total thickness
     extracted by ammonium oxalate) times 60] plus the                of 18 cm or more within 75 cm of the soil surface, one or
     volcanic glass (percent) is 30 or more.                          both of the following:
                                    Vitrixerandic Natrigypsids
                                                                         a. More than 35 percent (by volume) fragments coarser
GDBE. Other Natrigypsids that have, throughout one or more               than 2.0 mm, of which more than 66 percent is cinders,
horizons with a total thickness of 18 cm or more within 75 cm            pumice, and pumicelike fragments; or
of the soil surface, one or both of the following:
                                                                         b. A fine-earth fraction containing 30 percent or more
  1. More than 35 percent (by volume) fragments coarser                  particles 0.02 to 2.0 mm in diameter, of which 5 percent
  than 2.0 mm, of which more than 66 percent is cinders,                 or more is volcanic glass, and [(Al plus 1/2 Fe, percent
  pumice, and pumicelike fragments; or
122



      extracted by ammonium oxalate) times 60] plus the              GBB. Other Salids.
      volcanic glass (percent) is 30 or more.                                                                 Haplosalids, p. 122
                                     Vitrixerandic Petrogypsids
                                                                     Aquisalids
GDAD. Other Petrogypsids that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm        Key to Subgroups
of the soil surface, one or both of the following:                   GBAA. Aquisalids that have a gypsic or petrogypsic horizon
   1. More than 35 percent (by volume) fragments coarser             within 100 cm of the soil surface.
   than 2.0 mm, of which more than 66 percent is cinders,                                                      Gypsic Aquisalids
   pumice, and pumicelike fragments; or
                                                                     GBAB. Other Aquisalids that have a calcic or petrocalcic
   2. A fine-earth fraction containing 30 percent or more            horizon within 100 cm of the soil surface.
   particles 0.02 to 2.0 mm in diameter, of which 5 percent or                                                  Calcic Aquisalids
   more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted
   by ammonium oxalate) times 60] plus the volcanic glass            GBAC. Other Aquisalids.
   (percent) is 30 or more.                                                                                     Typic Aquisalids
                                         Vitrandic Petrogypsids
                                                                     Haplosalids
GDAE. Other Petrogypsids that, in normal years, are dry in all
parts of the moisture control section for less than three-fourths    Key to Subgroups
of the time (cumulative) when the soil temperature at a depth        GBBA. Haplosalids that have a duripan within 100 cm of the
of 50 cm below the soil surface is 5 oC or higher and have a soil    soil surface.
moisture regime that borders on xeric.                                                                        Duric Haplosalids
                                               Xeric Petrogypsids
                                                                     GBBB. Other Haplosalids that have a petrogypsic horizon
GDAF. Other Petrogypsids that, in normal years, are dry in all       within 100 cm of the soil surface.
parts of the moisture control section for less than three-fourths                                       Petrogypsic Haplosalids
of the time (cumulative) when the soil temperature at a depth
of 50 cm below the soil surface is 5 oC or higher and have a soil    GBBC. Other Haplosalids that have a gypsic horizon within
moisture regime that borders on ustic.                               100 cm of the soil surface.
                                               Ustic Petrogypsids                                           Gypsic Haplosalids

GDAG. Other Petrogypsids.                                            GBBD. Other Haplosalids that have a calcic horizon within
                                             Typic Petrogypsids      100 cm of the soil surface.
                                                                                                              Calcic Haplosalids
Salids
                                                                     GBBE. Other Haplosalids.
Key to Great Groups                                                                                            Typic Haplosalids
GBA. Salids that are saturated with water in one or more
layers within 100 cm of the mineral soil surface for 1 month or
more in normal years.
                                              Aquisalids, p. 122
                                                                                                                                   123




CHAPTER 8

                                                                                                                       Entisols

Key to Suborders                                                           c. Enough active ferrous iron to give a positive reaction
                                                                           to alpha,alpha-dipyridyl at a time when the soil is not
LA. Entisols that have a positive water potential at the soil              being irrigated.
surface for more than 21 hours of each day in all years.                                                             Aquents, p. 124
                                               Wassents, p. 142
                                                                   LC. Other Entisols that have, in one or more layers at a depth
LB. Other Entisols that have one or more of the following:         between 25 and 100 cm below the mineral soil surface, 3
  1. Aquic conditions and sulfidic materials within 50 cm of       percent or more (by volume) fragments of diagnostic horizons
  the mineral soil surface; or                                     that are not arranged in any discernible order.
                                                                                                                   Arents, p. 127
  2. Permanent saturation with water and a reduced matrix in
  all horizons below 25 cm from the mineral soil surface; or                                                                              E
                                                                   LD. Other Entisols that have less than 35 percent (by volume)          N
                                                                                                                                          T
  3. In a layer above a densic, lithic, or paralithic contact or   rock fragments and a texture class of loamy fine sand or coarser
  in a layer at a depth between 40 and 50 cm below the mineral     in all layers (sandy loam lamellae are permitted) within the
  soil surface, whichever is shallower, aquic conditions for       particle-size control section.
  some time in normal years (or artificial drainage) and one or                                                  Psamments, p. 138
  more of the following:
     a. A texture class finer than loamy fine sand and, in         LE. Other Entisols that do not have a densic, lithic, or
     50 percent or more of the matrix, one or more of the          paralithic contact within 25 cm of the mineral soil surface and
     following:                                                    have:

        (1)   Chroma of 0; or                                         1. A slope of less than 25 percent; and

        (2) Chroma of 1 or less and a color value, moist, of 4        2.    One or both of the following:
        or more; or                                                        a. An organic-carbon content (Holocene age) of 0.2
        (3)   Chroma of 2 or less and redox concentrations; or             percent or more at a depth of 125 cm below the mineral
                                                                           soil surface; or
     b. A texture class of loamy fine sand or coarser and,
     in 50 percent or more of the matrix, one or more of the               b. An irregular decrease in organic-carbon content
     following:                                                            (Holocene age) between a depth of 25 cm and either
                                                                           a depth of 125 cm below the mineral soil surface or
        (1)   Chroma of 0; or                                              a densic, lithic, or paralithic contact, whichever is
        (2) Hue of 10YR or redder, a color value, moist, of 4              shallower; and
        or more, and chroma of 1; or
                                                                      3. A soil temperature regime:
        (3) Hue of 10YR or redder, chroma of 2 or less, and
                                                                           a. That is warmer than cryic; or
        redox concentrations; or
                                                                           b. That is cryic and the soil has:
        (4) Hue of 2.5Y or yellower, chroma of 3 or less, and
        distinct or prominent redox concentrations; or                        (1)   No gelic materials; and
        (5)   Hue of 2.5Y or yellower and chroma of 1; or                     (2) Either a slope of less than 5 percent or less
                                                                              than 15 percent volcanic glass in the 0.02 to 2.0 mm
        (6)   Hue of 5GY, 5G, 5BG, or 5B; or
                                                                              fraction in some part of the particle-size control
        (7) Any color if it results from uncoated sand grains;                section.
        or                                                                                                             Fluvents, p. 128
124                                                                                                               Keys to Soil Taxonomy



LF.    Other Entisols.                                                     1. A fine-earth fraction with both a bulk density of 1.0
                                                  Orthents, p. 133         g/cm3 or less, measured at 33 kPa water retention, and Al
                                                                           plus 1/2 Fe percentages (by ammonium oxalate) totaling more
Aquents                                                                    than 1.0; or
                                                                           2. More than 35 percent (by volume) fragments coarser
Key to Great Groups                                                        than 2.0 mm, of which more than 66 percent is cinders,
LBA. Aquents that have sulfidic materials within 50 cm of the              pumice, and pumicelike fragments; or
mineral soil surface.
                                                                           3. A fine-earth fraction containing 30 percent or more
                                          Sulfaquents, p. 127
                                                                           particles 0.02 to 2.0 mm in diameter; and
LBB. Other Aquents that have, in all horizons at a depth                        a. In the 0.02 to 2.0 mm fraction, 5 percent or more
between 20 and 50 cm below the mineral soil surface, both an                    volcanic glass; and
n value of more than 0.7 and 8 percent or more clay in the fine-
                                                                                b. [(Al plus 1/2 Fe, percent extracted by ammonium
earth fraction.
                                                                                oxalate) times 60] plus the volcanic glass (percent) is
                                           Hydraquents, p. 126
                                                                                equal to 30 or more.
                                                                                                                    Aquandic Cryaquents
LBC. Other Aquents that have a gelic soil temperature regime.
                                           Gelaquents, p. 126
                                                                        LBDB. Other Cryaquents.
                                                                                                                      Typic Cryaquents
LBD.     Other Aquents that have a cryic soil temperature regime.
                                              Cryaquents, p. 124
                                                                        Endoaquents
LBE. Other Aquents that have less than 35 percent (by                   Key to Subgroups
volume) rock fragments and a texture class of loamy fine sand
or coarser in all layers (sandy loam lamellae are permitted)            LBHA. Endoaquents that have, within 100 cm of the mineral
within the particle-size control section.                               soil surface, one or both of the following:
                                          Psammaquents, p. 126             1.    Sulfidic materials; or

LBF. Other Aquents that have both:                                         2. A horizon 15 cm or more thick that has all of the
                                                                           characteristics of a sulfuric horizon, except that it has a pH
  1. A slope of less than 25 percent; and                                  value between 3.5 and 4.0 and does not have sulfide or other
  2.    One or both of the following:                                      sulfur-bearing minerals.
                                                                                                                      Sulfic Endoaquents
       a. At a depth of 125 cm below the mineral soil surface,
       an organic-carbon content (Holocene age) of 0.2 percent          LBHB. Other Endoaquents that have a lithic contact within 50
       or more; or                                                      cm of the mineral soil surface.
       b. An irregular decrease in organic-carbon content                                                      Lithic Endoaquents
       (Holocene age) between a depth of 25 cm and either
       a depth of 125 cm below the mineral soil surface or a            LBHC. Other Endoaquents that have, in one or more horizons
       densic, lithic, or paralithic contact, whichever is shallower.   within 100 cm of the mineral soil surface, an exchangeable
                                                Fluvaquents, p. 125     sodium percentage of 15 or more (or a sodium adsorption ratio
                                                                        of 13 or more) for 6 or more months in normal years.
LBG.     Other Aquents that have episaturation.                                                                     Sodic Endoaquents
                                             Epiaquents, p. 125
                                                                        LBHD. Other Endoaquents that have, in one or more horizons
LBH.     Other Aquents.                                                 between either the Ap horizon or a depth of 25 cm from the
                                              Endoaquents, p. 124       mineral soil surface, whichever is deeper, and a depth of 75 cm,
                                                                        colors in 50 percent or more of the matrix as follows:
Cryaquents                                                                 1. Hue of 2.5Y or redder, a color value, moist, of 6 or
                                                                           more, and chroma of 3 or more; or
Key to Subgroups
                                                                           2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
LBDA. Cryaquents that have, throughout one or more
                                                                           and chroma of 2 or more; or
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or more of the following:                 3.    Hue of 5Y and chroma of 3 or more; or
Entisols                                                                                                                          125



   4. Hue of 5Y or redder and chroma of 2 or more if there are      mineral soil (unmixed) or between the mineral soil surface and a
   no redox concentrations.                                         depth of 15 cm after mixing.
                                         Aeric Endoaquents                                                     Mollic Epiaquents

LBHE.      Other Endoaquents that have both:                        LBGD. Other Epiaquents.
                                                                                                                 Typic Epiaquents
   1. A color value, moist, of 3 or less and a color value, dry,
   of 5 or less (crushed and smoothed sample) either throughout
   the upper 15 cm of the mineral soil (unmixed) or between the     Fluvaquents
   mineral soil surface and a depth of 15 cm after mixing; and      Key to Subgroups
   2. A base saturation (by NH4OAc) of less than 50 percent         LBFA. Fluvaquents that have, within 100 cm of the mineral
   in some part within 100 cm of the mineral soil surface.          soil surface, one or both of the following:
                                   Humaqueptic Endoaquents
                                                                      1.    Sulfidic materials; or
LBHF. Other Endoaquents that have a color value, moist,               2. A horizon 15 cm or more thick that has all of the
of 3 or less and a color value, dry, of 5 or less (crushed and        characteristics of a sulfuric horizon, except that it has a pH
smoothed sample) either throughout the upper 15 cm of the             value between 3.5 and 4.0 and does not have sulfide or other
mineral soil (unmixed) or between the mineral soil surface and a      sulfur-bearing minerals.
depth of 15 cm after mixing.                                                                                      Sulfic Fluvaquents
                                               Mollic Endoaquents
                                                                                                                                        E
                                                                    LBFB. Other Fluvaquents that have one or both of the                N
LBHG.      Other Endoaquents.                                       following:                                                          T
                                              Typic Endoaquents
                                                                      1. Cracks within 125 cm of the mineral soil surface that are
Epiaquents                                                            5 mm or more wide through a thickness of 30 cm or more
                                                                      for some time in normal years and slickensides or wedge-
Key to Subgroups                                                      shaped peds in a layer 15 cm or more thick that has its upper
LBGA. Epiaquents that have, in one or more horizons                   boundary within 125 cm of the mineral soil surface; or
between either the Ap horizon or a depth of 25 cm from the            2. A linear extensibility of 6.0 cm or more between the
mineral soil surface, whichever is deeper, and a depth of 75 cm,      mineral soil surface and either a depth of 100 cm or a densic,
colors in 50 percent or more of the matrix as follows:                lithic, or paralithic contact, whichever is shallower.
   1. Hue of 2.5Y or redder, a color value, moist, of 6 or                                                        Vertic Fluvaquents
   more, and chroma of 3 or more; or
                                                                    LBFC. Other Fluvaquents that have a buried layer of organic
   2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
                                                                    soil materials, 20 cm or more thick, within 100 cm of the
   and chroma of 2 or more; or
                                                                    mineral soil surface.
   3.   Hue of 5Y and chroma of 3 or more; or                                                           Thapto-Histic Fluvaquents
   4. Chroma of 2 or more if there are no redox
   concentrations.                                                  LBFD. Other Fluvaquents that have, throughout one or more
                                            Aeric Epiaquents        horizons with a total thickness of 18 cm or more within 75 cm
                                                                    of the mineral soil surface, one or more of the following:
LBGB.      Other Epiaquents that have both:                           1. A fine-earth fraction with both a bulk density of 1.0
   1. A color value, moist, of 3 or less and a color value, dry,      g/cm3 or less, measured at 33 kPa water retention, and Al
   of 5 or less (crushed and smoothed sample) either throughout       plus 1/2 Fe percentages (by ammonium oxalate) totaling more
   the upper 15 cm of the mineral soil (unmixed) or between the       than 1.0; or
   mineral soil surface and a depth of 15 cm after mixing; and        2. More than 35 percent (by volume) fragments coarser
   2. A base saturation (by NH4OAc) of less than 50 percent           than 2.0 mm, of which more than 66 percent is cinders,
   in some part within 100 cm of the mineral soil surface.            pumice, and pumicelike fragments; or
                                     Humaqueptic Epiaquents           3. A fine-earth fraction containing 30 percent or more
                                                                      particles 0.02 to 2.0 mm in diameter; and
LBGC. Other Epiaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and             a. In the 0.02 to 2.0 mm fraction, 5 percent or more
smoothed sample) either throughout the upper 15 cm of the                  volcanic glass; and
126                                                                                                           Keys to Soil Taxonomy



        b. [(Al plus 1/2 Fe, percent extracted by ammonium             1.   Sulfidic materials; or
        oxalate) times 60] plus the volcanic glass (percent) is
                                                                       2. A horizon 15 cm or more thick that has all of the
        equal to 30 or more.
                                                                       characteristics of a sulfuric horizon, except that it has a pH
                                           Aquandic Fluvaquents
                                                                       value between 3.5 and 4.0 and does not have sulfide or other
                                                                       sulfur-bearing minerals.
LBFE. Other Fluvaquents that have, in one or more horizons
                                                                                                                  Sulfic Hydraquents
between either the Ap horizon or a depth of 25 cm from the
mineral soil surface, whichever is deeper, and a depth of 75 cm,
                                                                    LBBB. Other Hydraquents that have, in one or more horizons
colors in 50 percent or more of the matrix as follows:
                                                                    within 100 cm of the mineral soil surface, an exchangeable
   1. Hue of 2.5Y or redder, a color value, moist, of 6 or          sodium percentage of 15 or more (or a sodium adsorption ratio
   more, and chroma of 3 or more; or                                of 13 or more) for 6 or more months in normal years.
                                                                                                                Sodic Hydraquents
   2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,
   and chroma of 2 or more; or                                      LBBC. Other Hydraquents that have a buried layer of organic
   3.    Hue of 5Y and chroma of 3 or more; or                      soil materials, 20 cm or more thick, within 100 cm of the
                                                                    mineral soil surface.
   4. Chroma of 2 or more if there are no redox                                                        Thapto-Histic Hydraquents
   concentrations.
                                           Aeric Fluvaquents        LBBD. Other Hydraquents.
                                                                                                                Typic Hydraquents
LBFF. Other Fluvaquents that have both:
   1. A color value, moist, of 3 or less and a color value,         Psammaquents
   dry, of 5 or less (crushed and smoothed sample) either           Key to Subgroups
   throughout the upper 15 cm of the mineral soil (unmixed) or
   between the mineral soil surface and a depth of 15 cm after      LBEA. Psammaquents that have a lithic contact within 50 cm
   mixing; and                                                      of the mineral soil surface.
                                                                                                         Lithic Psammaquents
   2. A base saturation (by NH4OAc) of less than 50 percent
   in some part within 100 cm of the mineral soil surface.          LBEB. Other Psammaquents that have, in one or more
                                   Humaqueptic Fluvaquents          horizons within 100 cm of the mineral soil surface, an
                                                                    exchangeable sodium percentage of 15 or more (or a sodium
LBFG. Other Fluvaquents that have a color value, moist,             adsorption ratio of 13 or more) for 6 or more months in normal
of 3 or less and a color value, dry, of 5 or less (crushed and      years.
smoothed sample) either throughout the upper 15 cm of the                                                     Sodic Psammaquents
mineral soil (unmixed) or between the mineral soil surface and a
depth of 15 cm after mixing.                                        LBEC. Other Psammaquents that have a horizon, 5 cm or
                                               Mollic Fluvaquents   more thick, either below an Ap horizon or at a depth of 18 cm
                                                                    or more from the mineral soil surface, whichever is deeper, that
LBFH. Other Fluvaquents.                                            has one or more of the following:
                                             Typic Fluvaquents
                                                                       1. In 25 percent or more of each pedon, cementation by
Gelaquents                                                             organic matter and aluminum, with or without iron; or

Key to Subgroups                                                       2. Al plus 1/2 Fe percentages (by ammonium oxalate)
                                                                       totaling 0.25 or more, and half that amount or less in an
LBCA. All Gelaquents.                                                  overlying horizon; or
                                              Typic Gelaquents
                                                                       3. An ODOE value of 0.12 or more, and a value half as
                                                                       high or lower in an overlying horizon.
Hydraquents                                                                                                 Spodic Psammaquents
Key to Subgroups
                                                                    LBED. Other Psammaquents that have both:
LBBA. Hydraquents that have, within 100 cm of the mineral
soil surface, one or both of the following:                            1. A color value, moist, of 3 or less and a color value, dry,
Entisols                                                                                                                         127



  of 5 or less (crushed and smoothed sample) either throughout      Torriarents
  the upper 15 cm of the mineral soil (unmixed) or between the
  mineral soil surface and a depth of 15 cm after mixing; and       Key to Subgroups

  2. A base saturation (by NH4OAc) of less than 50 percent          LCCA. Torriarents that have, in one or more horizons within
  in some part within 100 cm of the mineral soil surface.           100 cm of the mineral soil surface, 3 percent or more fragments
                               Humaqueptic Psammaquents             of a natric horizon.
                                                                                                                  Sodic Torriarents
LBEE. Other Psammaquents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and      LCCB. Other Torriarents that have, within 100 cm of the
smoothed sample) either throughout the upper 15 cm of the           mineral soil surface, 3 percent or more fragments of a duripan
mineral soil (unmixed) or between the mineral soil surface and a    or a petrocalcic horizon.
depth of 15 cm after mixing.                                                                                     Duric Torriarents
                                            Mollic Psammaquents
                                                                    LCCC. Other Torriarents.
LBEF.      Other Psammaquents.                                                                                  Haplic Torriarents
                                          Typic Psammaquents
                                                                    Udarents
Sulfaquents                                                         Key to Subgroups
Key to Subgroups                                                    LCDA. Udarents that have 3 percent or more fragments of an
                                                                                                                                        E
LBAA. Sulfaquents that have, in some horizons at a depth            argillic horizon in some horizon within 100 cm of the mineral       N
                                                                    soil surface and have a base saturation (by sum of cations) of 35   T
between 20 and 50 cm below the mineral soil surface, either or
both:                                                               percent or more in all parts within 100 cm of the mineral soil
                                                                    surface.
  1. An n value of 0.7 or less; or                                                                                    Alfic Udarents
  2.    Less than 8 percent clay in the fine-earth fraction.
                                              Haplic Sulfaquents    LCDB. Other Udarents that have 3 percent or more fragments
                                                                    of an argillic horizon in some horizon within 100 cm of the
LBAB.      Other Sulfaquents that have a histic epipedon.           mineral soil surface.
                                               Histic Sulfaquents                                                    Ultic Udarents

LBAC. Other Sulfaquents that have a buried layer of organic         LCDC. Other Udarents that have 3 percent or more fragments
soil materials, 20 cm or more thick, within 100 cm of the           of a mollic epipedon in some horizon within 100 cm of the
mineral soil surface.                                               mineral soil surface and have a base saturation (by sum of
                                     Thapto-Histic Sulfaquents      cations) of 35 percent or more in all parts within 100 cm of the
                                                                    mineral soil surface.
LBAD.      Other Sulfaquents.                                                                                        Mollic Udarents
                                              Typic Sulfaquents
                                                                    LCDD. Other Udarents.
Arents                                                                                                             Haplic Udarents

Key to Great Groups                                                 Ustarents
LCA. Arents that have an ustic soil moisture regime.                Key to Subgroups
                                             Ustarents, p. 127
                                                                    LCAA. All Ustarents.
LCB. Other Arents that have a xeric soil moisture regime.                                                         Haplic Ustarents
                                            Xerarents, p. 127
                                                                    Xerarents
LCC. Other Arents that have an aridic (or torric) soil moisture
                                                                    Key to Subgroups
regime.
                                           Torriarents, p. 127      LCBA. Xerarents that have, in one or more horizons within
                                                                    100 cm of the mineral soil surface, 3 percent or more fragments
LCD.    Other Arents.                                               of a natric horizon.
                                               Udarents, p. 127                                                     Sodic Xerarents
128                                                                                                              Keys to Soil Taxonomy



LCBB. Other Xerarents that have, within 100 cm of the                   2. A fine-earth fraction containing 30 percent or more
mineral soil surface, 3 percent or more fragments of a duripan          particles 0.02 to 2.0 mm in diameter; and
or a petrocalcic horizon.
                                                                             a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                               Duric Xerarents
                                                                             volcanic glass; and
LCBC. Other Xerarents that have fragments of an argillic                     b. [(Al plus 1/2 Fe, percent extracted by ammonium
horizon with a base saturation (by sum of cations) of 35 percent             oxalate) times 60] plus the volcanic glass (percent) is
or more within 100 cm of the mineral soil surface.                           equal to 30 or more.
                                                Alfic Xerarents                                                 Vitrandic Cryofluvents

LCBD. Other Xerarents.                                               LEBC. Other Cryofluvents that have, in one or more horizons
                                              Haplic Xerarents       within 50 cm of the mineral soil surface, redox depletions with
                                                                     chroma of 2 or less and also aquic conditions for some time in
Fluvents                                                             normal years (or artificial drainage).
                                                                                                                  Aquic Cryofluvents
Key to Great Groups                                                  LEBD. Other Cryofluvents that are saturated with water in
LEA.   Fluvents that that have a gelic soil temperature regime.      one or more layers within 100 cm of the mineral soil surface in
                                              Gelifluvents, p. 128   normal years for either or both:
                                                                        1.    20 or more consecutive days; or
LEB. Other Fluvents that have a cryic soil temperature
regime.                                                                 2.    30 or more cumulative days.
                                         Cryofluvents, p. 128                                                   Oxyaquic Cryofluvents

LEC. Other Fluvents that have a xeric soil moisture regime.          LEBE. Other Cryofluvents that have a color value, moist,
                                         Xerofluvents, p. 132        of 3 or less and a color value, dry, of 5 or less (crushed and
                                                                     smoothed sample) either throughout the upper 15 cm of the
LED.   Other Fluvents that have an ustic soil moisture regime.       mineral soil (unmixed) or between the mineral soil surface and a
                                            Ustifluvents, p. 131     depth of 15 cm after mixing.
                                                                                                                    Mollic Cryofluvents
LEE. Other Fluvents that have an aridic (or torric) soil
moisture regime.                                                     LEBF. Other Cryofluvents.
                                         Torrifluvents, p. 128                                                     Typic Cryofluvents

LEF. Other Fluvents.                                                 Gelifluvents
                                             Udifluvents, p. 130
                                                                     Key to Subgroups
Cryofluvents                                                         LEAA. Gelifluvents that have, in one or more horizons within
                                                                     100 cm of the mineral soil surface, both redox depletions with
Key to Subgroups
                                                                     chroma of 2 or less and aquic conditions for some time in
LEBA. Cryofluvents that have, throughout one or more                 normal years (or artificial drainage).
horizons with a total thickness of 18 cm or more within 75                                                        Aquic Gelifluvents
cm of the mineral soil surface, a fine-earth fraction with both      LEAB. Other Gelifluvents.
a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water                                                     Typic Gelifluvents
retention, and percent aluminum plus 1/2 the iron percentage (by
ammonium oxalate) totaling more than 1.0.                            Torrifluvents
                                              Andic Cryofluvents
                                                                     Key to Subgroups
LEBB. Other Cryofluvents that have, throughout one or more           LEEA. Torrifluvents that have:
horizons with a total thickness of 18 cm or more within 75 cm
of the mineral soil surface, one or both of the following:              1.    One or both of the following:

  1. More than 35 percent (by volume) fragments coarser                      a. Cracks within 125 cm of the mineral soil surface that
  than 2.0 mm, of which more than 66 percent is cinders,                     are 5 mm or more wide through a thickness of 30 cm or
  pumice, and pumicelike fragments; or                                       more for some time in normal years and slickensides or
Entisols	                                                                                                                             129



      wedge-shaped	peds	in	a	layer	15	cm	or	more	thick	that	           LEED.	 Other	Torrifluvents	that	have,	throughout	one	or	more	
      has	its	upper	boundary	within	125	cm	of	the	mineral	soil	        horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
      surface;	or                                                      of	the	mineral	soil	surface,	one or both	of	the	following:
      b.	 A	linear	extensibility	of	6.0	cm	or	more	between	               1.	 More	than	35	percent	(by	volume)	fragments	coarser	
      the	mineral	soil	surface	and	either	a	depth	of	100	cm	              than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	
      or	a	densic,	lithic,	or	paralithic	contact,	whichever	is	           pumice,	and	pumicelike	fragments;	or
      shallower;	and
                                                                          2.	 A	fine-earth	fraction	containing	30	percent	or	more	
   2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	       particles	0.02	to	2.0	mm	in	diameter;	and
   all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
                                                                             a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	
   year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
                                                                             volcanic	glass;	and
   soil	surface	is	5	oC	or	higher;	and
                                                                             b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
   3.	 An	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
                                                                             oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
   ustic.
                                                                             equal	to	30	or	more.
                                           Ustertic Torrifluvents
                                                                                                                 Vitrandic Torrifluvents
LEEB.	 Other	Torrifluvents	that	have	one or both	of	the	
                                                                       LEEE.	 Other	Torrifluvents	that	have,	in	one	or	more	horizons	
following:
                                                                       within	100	cm	of	the	soil	surface,	both	redox	depletions	with	
   1.	 Cracks	within	125	cm	of	the	soil	surface	that	are	5	mm	         chroma	of	2	or	less	and	aquic	conditions	for	some	time	in	
   or	more	wide	through	a	thickness	of	30	cm	or	more	for	              normal	years	(or	artificial	drainage).                                 E
                                                                                                                                              N
   some	time	in	most	normal	years	and	slickensides	or	wedge-                                                       Aquic Torrifluvents        T
   shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	
   boundary	within	125	cm	of	the	soil	surface;	or                      LEEF.	 Other	Torrifluvents	that	are	saturated	with	water	in	one	
                                                                       or	more	layers	within	150	cm	of	the	soil	surface	in	normal	years	
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	soil	
                                                                       for	either or both:
   surface	and	either	a	depth	of	100	cm	or	a	densic,	lithic,	or	
   paralithic	contact,	whichever	is	shallower.                            1.	 20	or	more	consecutive	days;	or
                                            Vertic Torrifluvents
                                                                          2.	 30	or	more	cumulative	days.
                                                                                                                Oxyaquic Torrifluvents
LEEC.	 Other	Torrifluvents	that	have:
   1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	    LEEG.	 Other	Torrifluvents	that	have:
   all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
                                                                          1.	 A	horizon	within	100	cm	of	the	mineral	soil	surface	that	
   year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
                                                                          is	15	cm	or	more	thick	and	that	either	has	20	percent	or	more	
   soil	surface	is	5	oC	or	higher;	and
                                                                          (by	volume)	durinodes	or	is	brittle	and	has	at	least	a	firm	
   2.	 A	thermic,	mesic,	or	frigid	soil	temperature	regime	and	           rupture-resistance	class	when	moist;	and
   an	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
   xeric;	and                                                             2.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
                                                                          all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
   3.	 Throughout	one	or	more	horizons	with	a	total	thickness	            year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
   of	18	cm	or	more	within	75	cm	of	the	mineral	soil	surface,	            soil	surface	is	5	oC	or	higher;	and
   one or both	of	the	following:
                                                                          3.	 A	thermic,	mesic,	or	frigid	soil	temperature	regime	and	
      a.	 More	than	35	percent	(by	volume)	fragments	coarser	             an	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
      than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	             xeric.
      pumice,	and	pumicelike	fragments;	or                                                                     Duric Xeric Torrifluvents
      b.	 A	fine-earth	fraction	containing	30	percent	or	more	
      particles	0.02	to	2.0	mm	in	diameter;	and                        LEEH.	 Other	Torrifluvents	that	have	a	horizon	within	100	cm	
                                                                       of	the	mineral	soil	surface	that	is	15	cm	or	more	thick	and	that	
            (1)	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	    either	has	20	percent	or	more	(by	volume)	durinodes	or	is	brittle	
            volcanic	glass;	and                                        and	has	at	least	a	firm	rupture-resistance	class	when	moist.
            (2)	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	                                                    Duric Torrifluvents
            oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
            equal	to	30	or	more.                                       LEEI.	 Other	Torrifluvents	that	have	both:
                                        Vitrixerandic Torrifluvents
130                                                                                                            Keys to Soil Taxonomy



  1. A moisture control section that, in normal years, is dry in     LEFB. Other Udifluvents that have one or both of the
  all parts for less than three-fourths of the cumulative days per   following:
  year when the soil temperature at a depth of 50 cm below the
                                                                        1. Cracks within 125 cm of the mineral soil surface that are
  soil surface is 5 oC or higher; and
                                                                        5 mm or more wide through a thickness of 30 cm or more
  2. An aridic (or torric) soil moisture regime that borders on         for some time in normal years and slickensides or wedge-
  ustic.                                                                shaped peds in a layer 15 cm or more thick that has its upper
                                            Ustic Torrifluvents         boundary within 125 cm of the mineral soil surface; or

LEEJ.    Other Torrifluvents that have both:                            2. A linear extensibility of 6.0 cm or more between the
                                                                        mineral soil surface and either a depth of 100 cm or a densic,
  1. A moisture control section that, in normal years, is dry in        lithic, or paralithic contact, whichever is shallower.
  all parts for less than three-fourths of the cumulative days per                                                   Vertic Udifluvents
  year when the soil temperature at a depth of 50 cm below the
  soil surface is 5 oC or higher; and                                LEFC. Other Udifluvents that have, throughout one or more
  2. A thermic, mesic, or frigid soil temperature regime and         horizons with a total thickness of 18 cm or more within 75 cm
  an aridic (or torric) soil moisture regime that borders on         of the mineral soil surface, a fine-earth fraction with both a bulk
  xeric.                                                             density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
                                             Xeric Torrifluvents     and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
                                                                     more than 1.0.
LEEK. Other Torrifluvents that have an anthropic epipedon.                                                            Andic Udifluvents
                                    Anthropic Torrifluvents
                                                                     LEFD. Other Udifluvents that have, throughout one or more
LEEL.     Other Torrifluvents.                                       horizons with a total thickness of 18 cm or more within 75 cm
                                               Typic Torrifluvents   of the mineral soil surface, one or both of the following:
                                                                        1. More than 35 percent (by volume) fragments coarser
Udifluvents                                                             than 2.0 mm, of which more than 66 percent is cinders,
                                                                        pumice, and pumicelike fragments; or
Key to Subgroups
LEFA.     Udifluvents that have both:                                   2. A fine-earth fraction containing 30 percent or more
                                                                        particles 0.02 to 2.0 mm in diameter; and
  1.    One or both of the following:
                                                                           a. In the 0.02 to 2.0 mm fraction, 5 percent or more
       a. Cracks within 125 cm of the mineral soil surface that            volcanic glass; and
       are 5 mm or more wide through a thickness of 30 cm or
       more for some time in normal years and slickensides or              b. [(Al plus 1/2 Fe, percent extracted by ammonium
       wedge-shaped peds in a layer 15 cm or more thick that               oxalate) times 60] plus the volcanic glass (percent) is
       has its upper boundary within 125 cm of the mineral soil            equal to 30 or more.
       surface; or                                                                                             Vitrandic Udifluvents

       b. A linear extensibility of 6.0 cm or more between           LEFE. Other Udifluvents that have either:
       the mineral soil surface and either a depth of 100 cm
       or a densic, lithic, or paralithic contact, whichever is         1. In one or more horizons within 50 cm of the mineral soil
       shallower; and                                                   surface, redox depletions with chroma of 2 or less and also
                                                                        aquic conditions for some time in normal years (or artificial
  2.    Either or both of the following:                                drainage); or
       a. In one or more horizons within 50 cm of the mineral
                                                                        2. In one or more horizons within 100 cm of the mineral
       soil surface, redox depletions with chroma of 2 or less and
                                                                        soil surface, a color value, moist, of 4 or more and either
       also aquic conditions for some time in normal years (or
                                                                        chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic
       artificial drainage); or
                                                                        conditions for some time in normal years (or artificial
       b. In one or more horizons within 100 cm of the mineral          drainage).
       soil surface, a color value, moist, of 4 or more and                                                          Aquic Udifluvents
       either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and
       also aquic conditions for some time in normal years (or       LEFF. Other Udifluvents that are saturated with water in one
       artificial drainage).                                         or more layers within 100 cm of the mineral soil surface in
                                              Aquertic Udifluvents   normal years for either or both:
Entisols                                                                                                                                131



   1.    20 or more consecutive days; or                                      b. A mesic or thermic soil temperature regime and a
                                                                              moisture control section that, in normal years, is dry in
   2.    30 or more cumulative days.
                                                                              some part for six-tenths or more of the cumulative days
                                              Oxyaquic Udifluvents
                                                                              per year when the soil temperature at a depth of 50 cm
                                                                              below the soil surface is higher than 5 oC; or
LEFG. Other Udifluvents that have a color value, moist,
of 3 or less and a color value, dry, of 5 or less (crushed and                c. A hyperthermic, isomesic, or warmer iso soil
smoothed sample) either throughout the upper 15 cm of the                     temperature regime and a moisture control section that,
mineral soil (unmixed) or between the mineral soil surface and a              in normal years, remains moist in some or all parts for
depth of 15 cm after mixing.                                                  less than 90 consecutive days per year when the soil
                                                Mollic Udifluvents            temperature at a depth of 50 cm below the soil surface is
                                                                              higher than 8 oC; and
LEFH.      Other Udifluvents.
                                                                           2. One or both of the following:
                                                  Typic Udifluvents
                                                                              a. Cracks within 125 cm of the mineral soil surface that
Ustifluvents                                                                  are 5 mm or more wide through a thickness of 30 cm or
                                                                              more for some time in normal years and slickensides or
Key to Subgroups                                                              wedge-shaped peds in a layer 15 cm or more thick that
LEDA.      Ustifluvents that have both:                                       has its upper boundary within 125 cm of the mineral soil
                                                                              surface; or
   1.    One or both of the following:
                                                                              b. A linear extensibility of 6.0 cm or more between the          E
        a. Cracks within 125 cm of the mineral soil surface that                                                                               N
                                                                              mineral soil surface and either a depth of 100 cm or a           T
        are 5 mm or more wide through a thickness of 30 cm or                 densic, lithic, or paralithic contact, whichever is shallower.
        more for some time in normal years and slickensides or                                                       Torrertic Ustifluvents
        wedge-shaped peds in a layer 15 cm or more thick that
        has its upper boundary within 125 cm of the mineral soil         LEDC. Other Ustifluvents that have one or both of the
        surface; or                                                      following:
        b. A linear extensibility of 6.0 cm or more between                1. Cracks within 125 cm of the mineral soil surface that are
        the mineral soil surface and either a depth of 100 cm              5 mm or more wide through a thickness of 30 cm or more
        or a densic, lithic, or paralithic contact, whichever is           for some time in normal years and slickensides or wedge-
        shallower; and                                                     shaped peds in a layer 15 cm or more thick that has its upper
   2.    Either or both of the following:                                  boundary within 125 cm of the mineral soil surface; or
        a. In one or more horizons within 50 cm of the mineral             2. A linear extensibility of 6.0 cm or more between the
        soil surface, redox depletions with chroma of 2 or less and        mineral soil surface and either a depth of 100 cm or a densic,
        also aquic conditions for some time in normal years (or            lithic, or paralithic contact, whichever is shallower.
        artificial drainage); or                                                                                        Vertic Ustifluvents
        b. In one or more horizons within 150 cm of the mineral
                                                                         LEDD. Other Ustifluvents that have anthraquic conditions.
        soil surface, a color value, moist, of 4 or more and
                                                                                                             Anthraquic Ustifluvents
        either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and
        also aquic conditions for some time in normal years (or
                                                                         LEDE. Other Ustifluvents that have either:
        artificial drainage).
                                              Aquertic Ustifluvents        1. In one or more horizons within 50 cm of the mineral soil
                                                                           surface, redox depletions with chroma of 2 or less and also
LEDB.      Other Ustifluvents that have both of the following:
                                                                           aquic conditions for some time in normal years (or artificial
   1. When neither irrigated nor fallowed to store moisture,               drainage); or
   one of the following:
                                                                           2. In one or more horizons within 150 cm of the mineral
        a. A frigid soil temperature regime and a moisture                 soil surface, a color value, moist, of 4 or more and either
        control section that, in normal years, is dry in all parts for     chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic
        four-tenths or more of the cumulative days per year when           conditions for some time in normal years (or artificial
        the soil temperature at a depth of 50 cm below the soil            drainage).
        surface is higher than 5 oC; or                                                                                Aquic Ustifluvents
132                                                                                                          Keys to Soil Taxonomy



LEDF. Other Ustifluvents that are saturated with water in           mineral soil (unmixed) or between the mineral soil surface and a
one or more layers within 150 cm of the mineral soil surface in     depth of 15 cm after mixing.
normal years for either or both:                                                                               Mollic Ustifluvents
   1.   20 or more consecutive days; or
                                                                    LEDJ.   Other Ustifluvents.
   2.   30 or more cumulative days.                                                                              Typic Ustifluvents

                                          Oxyaquic Ustifluvents     Xerofluvents
LEDG. Other Ustifluvents that, when neither irrigated nor           Key to Subgroups
fallowed to store moisture, have one of the following:              LECA. Xerofluvents that have one or both of the following:
   1. A frigid soil temperature regime and a moisture control         1. Cracks within 125 cm of the mineral soil surface that are
   section that, in normal years, is dry in all parts for four-       5 mm or more wide through a thickness of 30 cm or more
   tenths or more of the cumulative days per year when the soil       for some time in normal years and slickensides or wedge-
   temperature at a depth of 50 cm below the soil surface is          shaped peds in a layer 15 cm or more thick that has its upper
   higher than 5 oC; or                                               boundary within 125 cm of the mineral soil surface; or
   2. A mesic or thermic soil temperature regime and a                2. A linear extensibility of 6.0 cm or more between the
   moisture control section that, in normal years, is dry in some     mineral soil surface and either a depth of 100 cm or a densic,
   part for six-tenths or more of the cumulative days per year        lithic, or paralithic contact, whichever is shallower.
   when the soil temperature at a depth of 50 cm below the soil                                                   Vertic Xerofluvents
   surface is higher than 5 oC; or
   3. A hyperthermic, isomesic, or warmer iso soil                  LECB. Other Xerofluvents that have:
   temperature regime and a moisture control section that, in         1. In one or more horizons within 50 cm of the mineral soil
   normal years, is moist in some or all parts for less than 180      surface, redox depletions with chroma of 2 or less and also
   cumulative days per year when the soil temperature at a            aquic conditions for some time in normal years (or artificial
   depth of 50 cm below the soil surface is higher than 8 oC.         drainage); or
                                              Aridic Ustifluvents
                                                                      2. In one or more horizons within 150 cm of the mineral
                                                                      soil surface, a color value, moist, of 4 or more and either
LEDH. Other Ustifluvents that, when neither irrigated nor
                                                                      chroma of 0 or hue bluer than 10Y and also aquic conditions
fallowed to store moisture, have one of the following:
                                                                      for some time in normal years (or artificial drainage); and
   1. A frigid soil temperature regime and a moisture control
                                                                      3. Throughout one or more horizons with a total thickness
   section that, in normal years, is dry in some or all parts
                                                                      of 18 cm or more within 75 cm of the mineral soil surface,
   for less than 105 cumulative days per year when the soil
                                                                      one or more of the following:
   temperature at a depth of 50 cm below the soil surface is
   higher than 5 oC; or                                                  a. A fine-earth fraction with both a bulk density of 1.0
   2. A mesic or thermic soil temperature regime and a                   g/cm3 or less, measured at 33 kPa water retention, and Al
                                                                         plus 1/2 Fe percentages (by ammonium oxalate) totaling
   moisture control section that, in normal years, is dry in some
                                                                         more than 1.0; or
   part for less than four-tenths of the cumulative days per year
   when the soil temperature at a depth of 50 cm below the soil          b. More than 35 percent (by volume) fragments coarser
   surface is higher than 5 oC; or                                       than 2.0 mm, of which more than 66 percent is cinders,
                                                                         pumice, and pumicelike fragments; or
   3. A hyperthermic, isomesic, or warmer iso soil
   temperature regime and a moisture control section that, in            c. A fine-earth fraction containing 30 percent or more
   normal years, is dry in some or all parts for less than 120           particles 0.02 to 2.0 mm in diameter; and
   cumulative days per year when the soil temperature at a
                                                                            (1) In the 0.02 to 2.0 mm fraction, 5 percent or more
   depth of 50 cm below the soil surface is higher than 8 oC.
                                                                            volcanic glass; and
                                                Udic Ustifluvents
                                                                            (2) [(Al plus 1/2 Fe, percent extracted by ammonium
LEDI. Other Ustifluvents that have a color value, moist,                    oxalate) times 60] plus the volcanic glass (percent) is
of 3 or less and a color value, dry, of 5 or less (crushed and              equal to 30 or more.
smoothed sample) either throughout the upper 15 cm of the                                                   Aquandic Xerofluvents
Entisols                                                                                                                            133



LECC. Other Xerofluvents that have, throughout one or more            mineral soil (unmixed) or between the mineral soil surface and a
horizons with a total thickness of 18 cm or more within 75 cm         depth of 15 cm after mixing.
of the mineral soil surface, a fine-earth fraction with both a bulk                                             Mollic Xerofluvents
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,
and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling         LECI.    Other Xerofluvents.
more than 1.0.                                                                                                    Typic Xerofluvents
                                               Andic Xerofluvents
                                                                      Orthents
LECD. Other Xerofluvents that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm         Key to Great Groups
of the mineral soil surface, one or both of the following:
                                                                      LFA.    Orthents that have a gelic soil temperature regime.
   1. More than 35 percent (by volume) fragments coarser                                                           Gelorthents, p. 134
   than 2.0 mm, of which more than 66 percent is cinders,
   pumice, and pumicelike fragments; or                               LFB. Other Orthents that have a cryic soil temperature regime.
                                                                                                                Cryorthents, p. 133
   2. A fine-earth fraction containing 30 percent or more
   particles 0.02 to 2.0 mm in diameter; and                          LFC. Other Orthents that have an aridic (or torric) soil
        a. In the 0.02 to 2.0 mm fraction, 5 percent or more          moisture regime.
        volcanic glass; and                                                                                   Torriorthents, p. 134
                                                                                                                                          E
        b. [(Al plus 1/2 Fe, percent extracted by ammonium            LFD. Other Orthents that have a xeric soil moisture regime.         N
        oxalate) times 60] plus the volcanic glass (percent) is                                                                           T
                                                                                                                 Xerorthents, p. 138
        equal to 30 or more.
                                           Vitrandic Xerofluvents     LFE. Other Orthents that have an ustic soil moisture regime.
                                                                                                                 Ustorthents, p. 136
LECE.      Other Xerofluvents that have either:
                                                                      LFF.    Other Orthents.
   1. In one or more horizons within 50 cm of the mineral soil
                                                                                                                   Udorthents, p. 135
   surface, redox depletions with chroma of 2 or less and also
   aquic conditions for some time in normal years (or artificial
   drainage); or                                                      Cryorthents
   2. In one or more horizons within 150 cm of the mineral            Key to Subgroups
   soil surface, a color value, moist, of 4 or more and either        LFBA. Cryorthents that have a lithic contact within 50 cm of
   chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic                 the mineral soil surface.
   conditions for some time in normal years.                                                                    Lithic Cryorthents
                                               Aquic Xerofluvents
                                                                      LFBB. Other Cryorthents that have, throughout one or more
LECF. Other Xerofluvents that are saturated with water in             horizons with a total thickness of 18 cm or more within 75 cm
one or more layers within 150 cm of the mineral soil surface in       of the mineral soil surface, one or both of the following:
normal years for either or both:
                                                                        1. More than 35 percent (by volume) fragments coarser
   1.    20 or more consecutive days; or                                than 2.0 mm, of which more than 66 percent is cinders,
                                                                        pumice, and pumicelike fragments; or
   2.    30 or more cumulative days.
                                           Oxyaquic Xerofluvents        2. A fine-earth fraction containing 30 percent or more
                                                                        particles 0.02 to 2.0 mm in diameter; and
LECG. Other Xerofluvents that have a horizon within 100 cm
                                                                             a. In the 0.02 to 2.0 mm fraction, 5 percent or more
of the mineral soil surface that is 15 cm or more thick and that
                                                                             volcanic glass; and
either has 20 percent or more (by volume) durinodes or is brittle
and has a firm rupture-resistance class when moist.                          b. [(Al plus 1/2 Fe, percent extracted by ammonium
                                         Durinodic Xerofluvents              oxalate) times 60] plus the volcanic glass (percent) is
                                                                             equal to 30 or more.
LECH. Other Xerofluvents that have a color value, moist,                                                         Vitrandic Cryorthents
of 3 or less and a color value, dry, of 5 or less (crushed and
smoothed sample) either throughout the upper 15 cm of the             LFBC. Other Cryorthents that have, in one or more horizons
134                                                                                                            Keys to Soil Taxonomy



within 50 cm of the mineral soil surface, redox depletions with       LFCB.   Other Torriorthents that have all of the following:
chroma of 2 or less and also aquic conditions for some time in
                                                                        1. A lithic contact within 50 cm of the soil surface; and
normal years (or artificial drainage).
                                             Aquic Cryorthents          2. A moisture control section that, in normal years, is dry in
                                                                        all parts for less than three-fourths of the cumulative days per
LFBD. Other Cryorthents that are saturated with water in                year when the soil temperature at a depth of 50 cm below the
one or more layers within 100 cm of the mineral soil surface in         soil surface is 5 oC or higher; and
normal years for either or both:
                                                                        3. A thermic, mesic, or frigid soil temperature regime and
   1.   20 or more consecutive days; or                                 an aridic (or torric) soil moisture regime that borders on
                                                                        xeric.
   2.   30 or more cumulative days.
                                                                                                            Lithic Xeric Torriorthents
                                          Oxyaquic Cryorthents
                                                                      LFCC. Other Torriorthents that have a lithic contact within 50
LFBE. Other Cryorthents that have lamellae within 200 cm of
                                                                      cm of the soil surface.
the mineral soil surface.
                                                                                                               Lithic Torriorthents
                                     Lamellic Cryorthents
                                                                      LFCD. Other Torriorthents that have:
LFBF. Other Cryorthents.
                                              Typic Cryorthents         1. One or both of the following:
                                                                           a. Cracks within 125 cm of the soil surface that are 5
Gelorthents                                                                mm or more wide through a thickness of 30 cm or more
Key to Subgroups                                                           for some time in normal years and slickensides or wedge-
                                                                           shaped peds in a layer 15 cm or more thick that has its
LFAA. Gelorthents that have, in one or more horizons within                upper boundary within 125 cm of the soil surface; or
100 cm of the mineral soil surface, both redox depletions with
chroma of 2 or less and aquic conditions for some time in                  b. A linear extensibility of 6.0 cm or more between the
normal years (or artificial drainage).                                     soil surface and either a depth of 100 cm or a densic,
                                             Aquic Gelorthents             lithic, or paralithic contact, whichever is shallower; and
                                                                        2. A moisture control section that, in normal years, is dry in
LFAB. Other Gelorthents that are saturated with water in one            all parts for less than three-fourths of the cumulative days per
or more layers within 100 cm of the mineral soil surface in             year when the soil temperature at a depth of 50 cm below the
normal years for either or both:                                        soil surface is 5 oC or higher; and
   1.   20 or more consecutive days; or                                 3. A thermic, mesic, or frigid soil temperature regime and
   2.   30 or more cumulative days.                                     an aridic (or torric) soil moisture regime that borders on
                                          Oxyaquic Gelorthents          xeric.
                                                                                                                Xerertic Torriorthents
LFAC. Other Gelorthents.
                                              Typic Gelorthents       LFCE.   Other Torriorthents that have:
                                                                        1. One or both of the following:
Torriorthents
                                                                           a. Cracks within 125 cm of the soil surface that are 5
Key to Subgroups                                                           mm or more wide through a thickness of 30 cm or more
                                                                           for some time in normal years and slickensides or wedge-
LFCA. Torriorthents that have all of the following:
                                                                           shaped peds in a layer 15 cm or more thick that has its
   1. A lithic contact within 50 cm of the soil surface; and               upper boundary within 125 cm of the soil surface; or
   2. A moisture control section that, in normal years, is dry in          b. A linear extensibility of 6.0 cm or more between the
   all parts for less than three-fourths of the cumulative days per        soil surface and either a depth of 100 cm or a densic,
   year when the soil temperature at a depth of 50 cm below the            lithic, or paralithic contact, whichever is shallower; and
   soil surface is 5 oC or higher; and
                                                                        2. A moisture control section that, in normal years, is dry in
   3. A hypertheric, thermic, mesic, frigid, or iso soil                all parts for less than three-fourths of the cumulative days per
   temperature regime and an aridic (or torric) soil moisture           year when the soil temperature at a depth of 50 cm below the
   regime that borders on ustic.                                        soil surface is 5 oC or higher; and
                                    Lithic Ustic Torriorthents
Entisols	                                                                                                                             135



   3.	 An	aridic	(or	torric)	soil	moisture	regime	that	borders	on	        1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
   ustic.                                                                 all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
                                          Ustertic Torriorthents          year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
                                                                          soil	surface	is	5	oC	or	higher;	and
LFCF.	 Other	Torriorthents	that	have	one or both	of	the	
                                                                          2.	 A	hyperthermic,	thermic,	mesic,	frigid,	or	iso	soil	
following:
                                                                          temperature	regime	and	an	aridic	(or	torric)	soil	moisture	
   1.	 Cracks	within	125	cm	of	the	soil	surface	that	are	5	mm	            regime	that	borders	on	ustic.
   or	more	wide	through	a	thickness	of	30	cm	or	more	for	some	                                                     Ustic Torriorthents
   time	in	normal	years	and	slickensides	or	wedge-shaped	peds	
   in	a	layer	15	cm	or	more	thick	that	has	its	upper	boundary	         LFCL.	 Other	Torriorthents	that	have	both:
   within	125	cm	of	the	soil	surface;	or
                                                                          1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	soil	         all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
   surface	and	either	a	depth	of	100	cm	or	a	densic,	lithic,	or	          year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
   paralithic	contact,	whichever	is	shallower.                            soil	surface	is	5	oC	or	higher;	and
                                            Vertic Torriorthents
                                                                          2.	 A	thermic,	mesic,	or	frigid	soil	temperature	regime		
LFCG.	 Other	Torriorthents	that	have,	throughout	one	or	more	             and	an	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	            xeric.
of	the	soil	surface,	one or both	of	the	following:                                                                   Xeric Torriorthents
                                                                                                                                              E
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	             LFCM.	 Other	Torriorthents.                                            N
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	                                                                                    T
                                                                                                                    Typic Torriorthents
   pumice,	and	pumicelike	fragments;	or
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	            Udorthents
   particles	0.02	to	2.0	mm	in	diameter;	and                           Key to Subgroups
      a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	           LFFA.	 Udorthents	that	have	a	lithic	contact	within	50	cm	of	
      volcanic	glass;	and                                              the	mineral	soil	surface.
      b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	                                                          Lithic Udorthents
      oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
      equal	to	30	or	more.                                             LFFB.	 Other	Udorthents	that	have,	throughout	one	or	more	
                                         Vitrandic Torriorthents       horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
                                                                       of	the	mineral	soil	surface,	one or both	of	the	following:
LFCH.	 Other	Torriorthents	that	have,	in	one	or	more	horizons	            1.	 More	than	35	percent	(by	volume)	fragments	coarser	
within	100	cm	of	the	soil	surface,	redox	depletions	with	chroma	          than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	
of	2	or	less	and	also	aquic	conditions	for	some	time	in	normal	           pumice,	and	pumicelike	fragments;	or
years	(or	artificial	drainage).
                                             Aquic Torriorthents          2.	 A	fine-earth	fraction	containing	30	percent	or	more	
                                                                          particles	0.02	to	2.0	mm	in	diameter;	and
LFCI.	 Other	Torriorthents	that	are	saturated	with	water	in	one	
                                                                             a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	
or	more	layers	within	150	cm	of	the	soil	surface	in	normal	years	
                                                                             volcanic	glass;	and
for	either or both:
                                                                             b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
   1.	 20	or	more	consecutive	days;	or
                                                                             oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
   2.	 30	or	more	cumulative	days.                                           equal	to	30	or	more.
                                        Oxyaquic Torriorthents                                                     Vitrandic Udorthents

LFCJ.	 Other	Torriorthents	that	have	a	horizon	within	100	cm	          LFFC.	 Other	Udorthents	that	have,	in	one	or	more	horizons	
of	the	soil	surface	that	is	15	cm	or	more	thick	and	that	either	has	   within	100	cm	of	the	mineral	soil	surface,	redox	depletions	with	
20	percent	or	more	(by	volume)	durinodes	or	is	brittle	and	has	at	     chroma	of	2	or	less	and	also	aquic	conditions	for	some	time	in	
least	a	firm	rupture-resistance	class	when	moist.                      normal	years	(or	artificial	drainage).
                                             Duric Torriorthents                                                     Aquic Udorthents

LFCK.	 Other	Torriorthents	that	have	both:                             LFFD.	 Other	Udorthents	that	are	saturated	with	water	in	one	
136	                                                                                                                 Keys	to	Soil	Taxonomy



or	more	layers	within	150	cm	of	the	mineral	soil	surface	in	                   are	5	mm	or	more	wide	through	a	thickness	of	30	cm	or	
normal	years	for	either or both:                                               more	for	some	time	in	normal	years	and	slickensides	or	
                                                                               wedge-shaped	peds	in	a	layer	15	cm	or	more	thick	that	
       1.	 20	or	more	consecutive	days;	or
                                                                               has	its	upper	boundary	within	125	cm	of	the	mineral	soil	
       2.	 30	or	more	cumulative	days.                                         surface;	or
                                             Oxyaquic Udorthents
                                                                               b.	 A	linear	extensibility	of	6.0	cm	or	more	between	
                                                                               the	mineral	soil	surface	and	either	a	depth	of	100	cm	
LFFE.	 Other	Udorthents	that	have	50	percent	or	more	(by	
                                                                               or	a	densic,	lithic,	or	paralithic	contact,	whichever	is	
volume)	wormholes,	wormcasts,	and	filled	animal	burrows	
                                                                               shallower;	and
between	either	the	Ap	horizon	or	a	depth	of	25	cm	from	the	
mineral	soil	surface,	whichever	is	deeper,	and	either	a	depth	              2.	 When	neither	irrigated	nor	fallowed	to	store	moisture,	
of	100	cm	or	a	densic,	lithic,	paralithic,	or	petroferric	contact,	         one	of	the	following:
whichever	is	shallower.
                                                                               a.	 A	frigid	soil	temperature	regime	and	a	moisture	
                                               Vermic Udorthents
                                                                               control	section	that,	in	normal	years,	is	dry	in	all	parts	for	
                                                                               four-tenths	or	more	of	the	cumulative	days	per	year	when	
LFFF.	 Other	Udorthents.
                                                                               the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	
                                                 Typic Udorthents
                                                                               surface	is	higher	than	5	oC;	or
Ustorthents                                                                    b.	 A	mesic	or	thermic	soil	temperature	regime	and	a	
                                                                               moisture	control	section	that,	in	normal	years,	is	dry	in	
Key to Subgroups                                                               some	part	for	six-tenths	or	more	of	the	cumulative	days	
LFEA.	 Ustorthents	that	have	both:                                             per	year	when	the	soil	temperature	at	a	depth	of	50	cm	
                                                                               below	the	soil	surface	is	higher	than	5	oC;	or
   1.	 A	lithic	contact	within	50	cm	of	the	mineral	soil	surface;	
   and                                                                         c.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	
                                                                               temperature	regime	and	a	moisture	control	section	that,	
   2.	 When	neither	irrigated	nor	fallowed	to	store	moisture,	
                                                                               in	normal	years,	remains	moist	in	some	or	all	parts	for	
   one	of	the	following:
                                                                               less	than	90	consecutive	days	per	year	when	the	soil	
       a.	 A	frigid	soil	temperature	regime	and	a	moisture	                    temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	
       control	section	that,	in	normal	years,	is	dry	in	all	parts	for	         higher	than	8	oC.
       four-tenths	or	more	of	the	cumulative	days	per	year	when	                                                   Torrertic Ustorthents
       the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	
       surface	is	higher	than	5	oC;	or                                   LFED.	 Other	Ustorthents	that	have	one or both	of	the	
                                                                         following:
       b.	 A	mesic	or	thermic	soil	temperature	regime	and	a	
       moisture	control	section	that,	in	normal	years,	is	dry	in	           1.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	are	
       some	part	for	six-tenths	or	more	of	the	cumulative	days	             5	mm	or	more	wide	through	a	thickness	of	30	cm	or	more	
       per	year	when	the	soil	temperature	at	a	depth	of	50	cm	              for	some	time	in	normal	years	and	slickensides	or	wedge-
       below	the	soil	surface	is	higher	than	5	oC;	or                       shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	
                                                                            boundary	within	125	cm	of	the	mineral	soil	surface;	or
       c.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	
       temperature	regime	and	a	moisture	control	section	that,	             2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	
       in	normal	years,	remains	moist	in	some	or	all	parts	for	             mineral	soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	
       less	than	90	consecutive	days	per	year	when	the	soil	                lithic,	or	paralithic	contact,	whichever	is	shallower.
       temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	                                                        Vertic Ustorthents
       higher	than	8	oC.
                                      Aridic Lithic Ustorthents          LFEE.	 Other	Ustorthents	that	have	anthraquic	conditions.
                                                                                                              Anthraquic Ustorthents
LFEB.	 Other	Ustorthents	that	have	a	lithic	contact	within	50	
cm	of	the	mineral	soil	surface.                                          LFEF.	 Other	Ustorthents	that	have,	in	one	or	more	horizons	
                                            Lithic Ustorthents           within	100	cm	of	the	mineral	soil	surface,	redox	depletions	with	
                                                                         chroma	of	2	or	less	and	also	aquic	conditions	for	some	time	in	
LFEC.	 Other	Ustorthents	that	have	both:                                 normal	years	(or	artificial	drainage).
                                                                                                                      Aquic Ustorthents
   1.	 One or both	of	the	following:
       a.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	        LFEG.	 Other	Ustorthents	that	are	saturated	with	water	in	
Entisols	                                                                                                                             137



one	or	more	layers	within	150	cm	of	the	mineral	soil	surface	in	          1.	 More	than	35	percent	(by	volume)	fragments	coarser	
normal	years	for	either or both:                                          than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	
                                                                          pumice,	and	pumicelike	fragments;	or
   1.	 20	or	more	consecutive	days;	or
                                                                          2.	 A	fine-earth	fraction	containing	30	percent	or	more	
   2.	 30	or	more	cumulative	days.
                                                                          particles	0.02	to	2.0	mm	in	diameter;	and
                                            Oxyaquic Ustorthents
                                                                             a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	
LFEH.	 Other	Ustorthents	that	have	a	horizon	within	100	cm	                  volcanic	glass;	and
of	the	mineral	soil	surface	that	is	15	cm	or	more	thick	and	that	
                                                                             b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
either	has	20	percent	or	more	(by	volume)	durinodes	or	is	brittle	
                                                                             oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
and	has	at	least	a	firm	rupture-resistance	class	when	moist.
                                                                             equal	to	30	or	more.
                                          Durinodic Ustorthents
                                                                                                                  Vitrandic Ustorthents
LFEI.	 Other	Ustorthents	that	have	both:
                                                                        LFEK.	 Other	Ustorthents	that,	when	neither	irrigated	nor	
   1.	 When	neither	irrigated	nor	fallowed	to	store	moisture,	          fallowed	to	store	moisture,	have	one	of	the	following:
   one	of	the	following:
                                                                          1.	 A	frigid	soil	temperature	regime	and	a	moisture	control	
      a.	 A	frigid	soil	temperature	regime	and	a	moisture	                section	that,	in	normal	years,	is	dry	in	all	parts	for	four-
      control	section	that,	in	normal	years,	is	dry	in	all	parts	for	     tenths	or	more	of	the	cumulative	days	per	year	when	the	soil	
      four-tenths	or	more	of	the	cumulative	days	per	year	when	           temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	
      the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	            higher	than	5	oC;	or                                              E
                                                                                                                                            N
      surface	is	higher	than	5	oC;	or                                                                                                       T
                                                                          2.	 A	mesic	or	thermic	soil	temperature	regime	and	a	
      b.	 A	mesic	or	thermic	soil	temperature	regime	and	a	               moisture	control	section	that,	in	normal	years,	is	dry	in	some	
      moisture	control	section	that,	in	normal	years,	is	dry	in	          part	for	six-tenths	or	more	of	the	cumulative	days	per	year	
      some	part	for	six-tenths	or	more	of	the	cumulative	days	            when	the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	
      per	year	when	the	soil	temperature	at	a	depth	of	50	cm	             surface	is	higher	than	5	oC;	or
      below	the	soil	surface	is	higher	than	5	oC;	or
                                                                          3.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	
      c.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	                   temperature	regime	and	a	moisture	control	section	that,	in	
      temperature	regime	and	a	moisture	control	section	that,	            normal	years,	is	moist	in	some	or	all	parts	for	less	than	180	
      in	normal	years,	remains	moist	in	some	or	all	parts	for	            cumulative	days	per	year	when	the	soil	temperature	at	a	
      less	than	90	consecutive	days	per	year	when	the	soil	               depth	of	50	cm	below	the	soil	surface	is	higher	than	8	oC.
      temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	                                                     Aridic Ustorthents
      higher	than	8	oC;	and
                                                                        LFEL.	 Other	Ustorthents	that,	when	neither	irrigated	nor	
   2.	 Throughout	one	or	more	horizons	with	a	total	thickness	
                                                                        fallowed	to	store	moisture,	have	one	of	the	following:
   of	18	cm	or	more	within	75	cm	of	the	soil	surface,	one or
   both	of	the	following:                                                 1.	 A	frigid	soil	temperature	regime	and	a	moisture	control	
                                                                          section	that,	in	normal	years,	is	dry	in	some	or	all	parts	
      a.	 More	than	35	percent	(by	volume)	fragments	coarser	
                                                                          for	less	than	105	cumulative	days	per	year	when	the	soil	
      than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	
                                                                          temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	
      pumice,	and	pumicelike	fragments;	or
                                                                          higher	than	5	oC;	or
      b.	 A	fine-earth	fraction	containing	30	percent	or	more	
                                                                          2.	 A	mesic	or	thermic	soil	temperature	regime	and	a	
      particles	0.02	to	2.0	mm	in	diameter;	and
                                                                          moisture	control	section	that,	in	normal	years,	is	dry	in	some	
            (1)	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	       part	for	less	than	four-tenths	of	the	cumulative	days	per	year	
            volcanic	glass;	and                                           when	the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	
                                                                          surface	is	higher	than	5	oC;	or
            (2)	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
            oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	      3.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	
            equal	to	30	or	more.                                          temperature	regime	and	a	moisture	control	section	that,	in	
                                        Vitritorrandic Ustorthents        normal	years,	is	dry	in	some	or	all	parts	for	less	than	120	
                                                                          cumulative	days	per	year	when	the	soil	temperature	at	a	
LFEJ.	 Other	Ustorthents	that	have,	throughout	one	or	more	               depth	of	50	cm	below	the	soil	surface	is	higher	than	8	oC.
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	                                                         Udic Ustorthents
of	the	soil	surface,	one or both	of	the	following:
138	                                                                                                             Keys	to	Soil	Taxonomy



LFEM.	 Other	Ustorthents	that	have	50	percent	or	more	(by	            LFDF.	 Other	Xerorthents	that	have	a	base	saturation	(by	
volume)	wormholes,	wormcasts,	and	filled	animal	burrows	              NH4OAc)	of	less	than	60	percent	in	all	horizons	at	a	depth	
between	either	the	Ap	horizon	or	a	depth	of	25	cm	from	the	           between	25	and	75	cm	below	the	mineral	soil	surface	or	in	the	
mineral	soil	surface,	whichever	is	deeper,	and	either	a	depth	        horizon	directly	above	a	root-limiting	layer	that	is	at	a	shallower	
of	100	cm	or	a	densic,	lithic,	paralithic,	or	petroferric	contact,	   depth.
whichever	is	shallower.                                                                                            Dystric Xerorthents
                                               Vermic Ustorthents
                                                                      LFDG.	 Other	Xerorthents.
LFEN.	 Other	Ustorthents.                                                                                            Typic Xerorthents
                                               Typic Ustorthents
                                                                      Psamments
Xerorthents
                                                                      Key to Great Groups
Key to Subgroups
                                                                      LDA.	 Psamments	that	have	a	cryic	soil	temperature	regime.
LFDA.	 Xerorthents	that	have	a	lithic	contact	within	50	cm	of	                                            Cryopsamments,	p.	138
the	mineral	soil	surface.
                                           Lithic Xerorthents         LDB.	 Other	Psamments	that	have	an	aridic	(or	torric)	soil	
                                                                      moisture	regime.
LFDB.	 Other	Xerorthents	that	have,	throughout	one	or	more	                                              Torripsamments,	p.	140
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
of	the	mineral	soil	surface,	one or both	of	the	following:            LDC.	 Other	Psamments	that	have,	in	the	0.02	to	2.0	mm	
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	            fraction	within	the	particle-size	control	section,	a	total	of	more	
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	            than	90	percent	(by	weighted	average)	resistant	minerals.
   pumice,	and	pumicelike	fragments;	or                                                                     Quartzipsamments,	p.	139
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	
                                                                      LDD.	 Other	Psamments	that	have	an	ustic	soil	moisture	
   particles	0.02	to	2.0	mm	in	diameter;	and
                                                                      regime.
       a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	                                             Ustipsamments,	p.	141
       volcanic	glass;	and
       b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	           LDE.	 Other	Psamments	that	have	a	xeric	soil	moisture	regime.
       oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	                                           Xeropsamments,	p.	141
       equal	to	30	or	more.
                                            Vitrandic Xerorthents     LDF.	 Other	Psamments.
                                                                                                                 Udipsamments,	p.	140
LFDC.	 Other	Xerorthents	that	have,	in	one	or	more	horizons	
within	100	cm	of	the	mineral	soil	surface,	redox	depletions	with	     Cryopsamments
chroma	of	2	or	less	and	also	aquic	conditions	for	some	time	in	
normal	years	(or	artificial	drainage).                                Key to Subgroups
                                             Aquic Xerorthents        LDAA.	 Cryopsamments	that	have	a	lithic	contact	within	50	
                                                                      cm	of	the	mineral	soil	surface.
LFDD.	 Other	Xerorthents	that	are	saturated	with	water	in	                                                Lithic Cryopsamments
one	or	more	layers	within	150	cm	of	the	mineral	soil	surface	in	
normal	years	for	either or both:                                      LDAB.	 Other	Cryopsamments	that	have,	in	one	or	more	
   1.	 20	or	more	consecutive	days;	or                                horizons	within	50	cm	of	the	mineral	soil	surface,	redox	
                                                                      depletions	with	chroma	of	2	or	less	and	also	aquic	conditions	
   2.	 30	or	more	cumulative	days.
                                                                      for	some	time	in	normal	years	(or	artificial	drainage).
                                          Oxyaquic Xerorthents
                                                                                                               Aquic Cryopsamments
LFDE.	 Other	Xerorthents	that	have	a	horizon	within	100	cm	
                                                                      LDAC.	 Other	Cryopsamments	that	are	saturated	with	water	in	
of	the	mineral	soil	surface	that	is	15	cm	or	more	thick	and	that	
                                                                      one	or	more	layers	within	100	cm	of	the	mineral	soil	surface	in	
either	has	20	percent	or	more	(by	volume)	durinodes	or	is	brittle	
                                                                      normal	years	for	either or both:
and	has	at	least	a	firm	rupture-resistance	class	when	moist.
                                          Durinodic Xerorthents          1.	 20	or	more	consecutive	days;	or
Entisols	                                                                                                                       139



   2.	 30	or	more	cumulative	days.                                       c.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	
                                     Oxyaquic Cryopsamments              high	or	lower	in	an	overlying	horizon.
                                                                                                      Aquodic Quartzipsamments
LDAD.	 Other	Cryopsamments	that	have,	throughout	one	or	
more	horizons	with	a	total	thickness	of	18	cm	or	more	within	75	    LDCC.	 Other	Quartzipsamments	that	have,	in	one	or	more	
cm	of	the	mineral	soil	surface,	a	fine-earth	fraction	containing	   horizons	within	100	cm	of	the	mineral	soil	surface,	redox	
5	percent	or	more	volcanic	glass,	and	[(Al	plus	1/2	Fe,	percent	    depletions	with	chroma	of	2	or	less	and	also	aquic	conditions	
extracted	by	ammonium	oxalate)	times	60]	plus	the	volcanic	         for	some	time	in	normal	years	(or	artificial	drainage).
glass	(percent)	is	30	or	more.                                                                           Aquic Quartzipsamments
                                      Vitrandic Cryopsamments
                                                                    LDCD.	 Other	Quartzipsamments	that	are	saturated	with	water	
LDAE.	 Other	Cryopsamments	that	have	a	horizon	5	cm	or	             in	one	or	more	layers	within	100	cm	of	the	mineral	soil	surface	
more	thick	that	has	one or more	of	the	following:                   in	normal	years	for	either or both:
   1.	 In	25	percent	or	more	of	each	pedon,	cementation	by	           1.	 20	or	more	consecutive	days;	or
   organic	matter	and	aluminum,	with	or	without	iron;	or
                                                                      2.	 30	or	more	cumulative	days.
   2.	 Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	                                          Oxyaquic Quartzipsamments
   totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	
   overlying	horizon;	or                                            LDCE.	 Other	Quartzipsamments	that	meet	all	of	the	
   3.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	          following:
                                                                                                                                       E
   high	or	lower	in	an	overlying	horizon.                             1.	 Have	an	ustic	soil	moisture	regime;	and                      N
                                                                                                                                       T
                                       Spodic Cryopsamments
                                                                      2.	 Have	a	clay	fraction	with	a	CEC	of	16	cmol(+)	or	less	
LDAF.	 Other	Cryopsamments	that	have	lamellae	within	200	             per	kg	clay	(by	1N	NH4OAc	pH	7);	and
cm	of	the	mineral	soil	surface.                                       3.	 The	sum	of	the	weighted	average	silt	plus	2	times	the	
                                Lamellic Cryopsamments                weighted	average	clay	(both	by	weight)	is	more	than	5.
                                                                                                      Ustoxic Quartzipsamments
LDAG.	 Other	Cryopsamments.
                                         Typic Cryopsamments        LDCF.	 Other	Quartzipsamments	that	meet	all	of	the	
                                                                    following:
Quartzipsamments
                                                                      1.	 Have	a	udic	soil	moisture	regime;	and
Key to Subgroups
                                                                      2.	 Have	a	clay	fraction	with	a	CEC	of	16	cmol(+)	or	less	
LDCA.	 Quartzipsamments	that	have	a	lithic	contact	within	50	         per	kg	clay	(by	1N	NH4OAc	pH	7);	and
cm	of	the	mineral	soil	surface.
                                Lithic Quartzipsamments               3.	 The	sum	of	the	weighted	average	silt	plus	2	times	the	
                                                                      weighted	average	clay	(both	by	weight)	is	more	than	5.
LDCB.	 Other	Quartzipsamments	that	have	both:                                                         Udoxic Quartzipsamments
   1.	 In	one	or	more	horizons	within	100	cm	of	the	mineral	
                                                                    LDCG.	 Other	Quartzipsamments	that	have	5	percent	or	more	
   soil	surface,	redox	depletions	with	chroma	of	2	or	less	and	
                                                                    (by	volume)	plinthite	in	one	or	more	horizons	within	100	cm	of	
   also	aquic	conditions	for	some	time	in	normal	years	(or	
                                                                    the	mineral	soil	surface.
   artificial	drainage);	and
                                                                                                       Plinthic Quartzipsamments
   2.	 A	horizon,	5	cm	or	more	thick,	either	below	an	Ap	
   horizon	or	at	a	depth	of	18	cm	or	more	from	the	mineral	soil	    LDCH.	 Other	Quartzipsamments	that	have	both:
   surface,	whichever	is	deeper,	that	has	one or more	of	the	
                                                                      1.	 Lamellae	within	200	cm	of	the	mineral	soil	surface;	and
   following:
                                                                      2.	 An	ustic	soil	moisture	regime.
      a.	 In	25	percent	or	more	of	each	pedon,	cementation	by	
                                                                                               Lamellic Ustic Quartzipsamments
      organic	matter	and	aluminum,	with	or	without	iron;	or
      b.	 Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	         LDCI.	 Other	Quartzipsamments	that	have	lamellae	within	200	
      totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	    cm	of	the	mineral	soil	surface.
      overlying	horizon;	or                                                                         Lamellic Quartzipsamments
140	                                                                                                            Keys	to	Soil	Taxonomy



LDCJ.	 Other	Quartzipsamments	that	have	an	ustic	soil	                LDBE.	 Other	Torripsamments	that	have	both:
moisture	regime.
                                                                         1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
                                 Ustic Quartzipsamments
                                                                         all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
                                                                         year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
LDCK.	 Other	Quartzipsamments	that	have	a	xeric	soil	                    soil	surface	is	5	oC	or	higher;	and
moisture	regime.
                                Xeric Quartzipsamments                   2.	 An	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
                                                                         ustic.
LDCL.	 Other	Quartzipsamments	that	have	a	horizon,	5	cm	or	                                                     Ustic Torripsamments
more	thick,	either	below	an	Ap	horizon	or	at	a	depth	of	18	cm	
or	more	from	the	mineral	soil	surface,	whichever	is	deeper,	that	     LDBF.	 Other	Torripsamments	that	have	both:
has	one or more	of	the	following:                                        1.	 A	moisture	control	section	that,	in	normal	years,	is	dry	in	
   1.	 In	25	percent	or	more	of	each	pedon,	cementation	by	              all	parts	for	less	than	three-fourths	of	the	cumulative	days	per	
   organic	matter	and	aluminum,	with	or	without	iron;	or                 year	when	the	soil	temperature	at	a	depth	of	50	cm	below	the	
                                                                         soil	surface	is	5	oC	or	higher;	and
   2.	 Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	
   totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	            2.	 A	thermic,	mesic,	or	frigid	soil	temperature	regime	and	
   overlying	horizon;	or                                                 an	aridic	(or	torric)	soil	moisture	regime	that	borders	on	
                                                                         xeric.
   3.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	                                                       Xeric Torripsamments
   high	or	lower	in	an	overlying	horizon.
                                     Spodic Quartzipsamments          LDBG.	 Other	Torripsamments	that	have,	in	all	horizons	from	
                                                                      a	depth	of	25	to	100	cm,	more	than	50	percent	colors	that	have	
LDCM.	 Other	Quartzipsamments.                                        all of	the	following:
                                      Typic Quartzipsamments
                                                                         1.	 Hue	of	2.5YR	or	redder;	and
Torripsamments                                                           2.	 A	color	value,	moist,	of	3	or	less;	and

Key to Subgroups                                                         3.	 A	dry	value	no	more	than	1	unit	higher	than	the	moist	
                                                                         value.
LDBA.	 Torripsamments	that	have	a	lithic	contact	within	50	                                                Rhodic Torripsamments
cm	of	the	soil	surface.
                                     Lithic Torripsamments            LDBH.	 Other	Torripsamments.
                                                                                                               Typic Torripsamments
LDBB.	 Other	Torripsamments	that	are	saturated	with	water	in	
one	or	more	layers	within	150	cm	of	the	mineral	soil	surface	in	      Udipsamments
normal	years	for	either or both:
                                                                      Key to Subgroups
       1.	 20	or	more	consecutive	days; or
                                                                      LDFA.	 Udipsamments	that	have	a	lithic	contact	within	50	cm	
       2.	 30	or	more	cumulative	days.                                of	the	mineral	soil	surface.
                                   Oxyaquic Torripsamments                                                  Lithic Udipsamments

LDBC.	 Other	Torripsamments	that	have,	throughout	one	or	             LDFB.	 Other	Udipsamments	that	have,	in	one	or	more	
more	horizons	with	a	total	thickness	of	18	cm	or	more	within	75	      horizons	within	100	cm	of	the	mineral	soil	surface,	redox	
cm	of	the	mineral	soil	surface,	a	fine-earth	fraction	containing	     depletions	with	chroma	of	2	or	less	and	also	aquic	conditions	
5	percent	or	more	volcanic	glass,	and	[(Al	plus	1/2	Fe,	percent	      for	some	time	in	normal	years	(or	artificial	drainage).
extracted	by	ammonium	oxalate)	times	60]	plus	the	volcanic	                                                      Aquic Udipsamments
glass	(percent)	is	30	or	more.
                                      Vitrandic Torripsamments        LDFC.	 Other	Udipsamments	that	are	saturated	with	water	in	
                                                                      one	or	more	layers	within	100	cm	of	the	mineral	soil	surface	in	
LDBD.	 Other	Torripsamments	that	have	a	horizon	within	100	           normal	years	for	either or both:
cm	of	the	soil	surface	that	is	15	cm	or	more	thick	and	that	either	
                                                                         1.	 20	or	more	consecutive	days;	or
has	20	percent	or	more	(by	volume)	durinodes	or	is	brittle	and	
has	at	least	a	firm	rupture-resistance	class	when	moist.                 2.	 30	or	more	cumulative	days.
                                  Haploduridic Torripsamments                                                Oxyaquic Udipsamments
Entisols	                                                                                                                        141



LDFD.	 Other	Udipsamments	that	have	a	horizon,	5	cm	or	               2.	 A	mesic	or	thermic	soil	temperature	regime	and	a	
more	thick,	either	below	an	Ap	horizon	or	at	a	depth	of	18	cm	        moisture	control	section	that,	in	normal	years,	is	dry	in	some	
or	more	from	the	mineral	soil	surface,	whichever	is	deeper,	that	     part	for	six-tenths	or	more	of	the	cumulative	days	per	year	
has	one or more	of	the	following:                                     when	the	soil	temperature	at	a	depth	of	50	cm	below	the	soil	
   1.	 In	25	percent	or	more	of	each	pedon,	cementation	by	           surface	is	higher	than	5	oC;	or
   organic	matter	and	aluminum,	with	or	without	iron;	or              3.	 A	hyperthermic,	isomesic,	or	warmer	iso	soil	
   2.	 Al	plus	 /2	Fe	percentages	(by	ammonium	oxalate)	
               1                                                      temperature	regime	and	a	moisture	control	section	that,	in	
   totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	         normal	years,	is	moist	in	some	or	all	parts	for	less	than	180	
   overlying	horizon;	or                                              cumulative	days	per	year	when	the	soil	temperature	at	a	
                                                                      depth	of	50	cm	below	the	soil	surface	is	higher	than	8	oC.
   3.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	                                                   Aridic Ustipsamments
   high	or	lower	in	an	overlying	horizon.
                                         Spodic Udipsamments        LDDE.	 Other	Ustipsamments	that	have	lamellae	within	200	
                                                                    cm	of	the	mineral	soil	surface.
LDFE.	 Other	Udipsamments	that	have	lamellae	within	200	cm	                                          Lamellic Ustipsamments
of	the	mineral	soil	surface.
                                  Lamellic Udipsamments             LDDF.	 Other	Ustipsamments	that	have,	in	all	horizons	from	a	
                                                                    depth	of	25	to	100	cm,	more	than	50	percent	colors	that	have	all
LDFF.	 Other	Udipsamments	that	have	a	surface	horizon	              of	the	following:
between	25	and	50	cm	thick	that	meets	all	of	the	requirements	
for	a	plaggen	epipedon	except	thickness.                              1.	 Hue	of	2.5YR	or	redder;	and                                   E
                                                                                                                                        N
                              Plagganthreptic Udipsamments                                                                              T
                                                                      2.	 A	color	value,	moist,	of	3	or	less;	and
LDFG.	 Other	Udipsamments.                                            3.	 A	dry	value	no	more	than	1	unit	higher	than	the	moist	
                                           Typic Udipsamments         value.
                                                                                                          Rhodic Ustipsamments
Ustipsamments
                                                                    LDDG.	 Other	Ustipsamments.
Key to Subgroups
                                                                                                             Typic Ustipsamments
LDDA.	 Ustipsamments	that	have	a	lithic	contact	within	50	cm	
of	the	mineral	soil	surface.                                        Xeropsamments
                                      Lithic Ustipsamments
                                                                    Key to Subgroups
LDDB.	 Other	Ustipsamments	that	have,	in	one	or	more	               LDEA.	 Xeropsamments	that	have	a	lithic	contact	within	50	
horizons	within	100	cm	of	the	mineral	soil	surface,	distinct	or	    cm	of	the	mineral	soil	surface.
prominent	redox	concentrations	and	also	aquic	conditions	for	                                           Lithic Xeropsamments
some	time	in	normal	years	(or	artificial	drainage).
                                          Aquic Ustipsamments       LDEB.	 Other	Xeropsamments	that	have	both:

LDDC.	 Other	Ustipsamments	that	are	saturated	with	water	in	          1.	 In	one	or	more	horizons	within	100	cm	of	the	mineral	
one	or	more	layers	within	100	cm	of	the	mineral	soil	surface	in	      soil	surface,	distinct	or	prominent	redox	concentrations	and	
normal	years	for	either or both:                                      also	aquic	conditions	for	some	time	in	normal	years	(or	
                                                                      artificial	drainage);	and
   1.	 20	or	more	consecutive	days;	or
                                                                      2.	 A	horizon	within	100	cm	of	the	mineral	soil	surface	that	
   2.	 30	or	more	cumulative	days.
                                                                      is	15	cm	or	more	thick	and	that	either	has	20	percent	or	more	
                                      Oxyaquic Ustipsamments
                                                                      (by	volume)	durinodes	or	is	brittle	and	has	at	least	a	firm	
                                                                      rupture-resistance	class	when	moist.
LDDD.	 Other	Ustipsamments	that,	when	neither	irrigated	nor	
                                                                                                Aquic Durinodic Xeropsamments
fallowed	to	store	moisture,	have	one	of	the	following:
   1.	 A	frigid	soil	temperature	regime	and	a	moisture	control	     LDEC.	 Other	Xeropsamments	that	have,	in	one	or	more	
   section	that,	in	normal	years,	is	dry	in	all	parts	for	four-     horizons	within	100	cm	of	the	mineral	soil	surface,	distinct	or	
   tenths	or	more	of	the	cumulative	days	per	year	when	the	soil	    prominent	redox	concentrations	and	also	aquic	conditions	for	
   temperature	at	a	depth	of	50	cm	below	the	soil	surface	is	       some	time	in	normal	years	(or	artificial	drainage).
   higher	than	5	oC;	or                                                                                      Aquic Xeropsamments
142	



LDED.	 Other	Xeropsamments	that	are	saturated	with	water	in	           LAD.	 Other	Wassents	that	have,	in	all	horizons	at	a	depth	
one	or	more	layers	within	100	cm	of	the	mineral	soil	surface	in	       between	20	and	50	cm	below	the	mineral	soil	surface,	both	an	
normal	years	for	either or both:                                       n	value	of	more	than	0.7	and	8	percent	or	more	clay	in	the	fine-
                                                                       earth	fraction.	
   1.	 20	or	more	consecutive	days;	or
                                                                                                                Hydrowassents,	p.	143
   2.	 30	or	more	cumulative	days.
                                      Oxyaquic Xeropsamments           LAE.	 Other	Wassents	that	have	one or both	of	the	following:
                                                                         1.	 At	a	depth	of	125	cm	below	the	mineral	soil	surface,	
LDEE.	 Other	Xeropsamments	that	have,	throughout	one	or	
                                                                         an	organic-carbon	content	(Holocene	age)	of	0.2	percent	or	
more	horizons	with	a	total	thickness	of	18	cm	or	more	within	75	
                                                                         more	and	no	densic,	lithic,	or	paralithic	contact	within	that	
cm	of	the	mineral	soil	surface,	a	fine-earth	fraction	containing	
                                                                         depth;	or	
5	percent	or	more	volcanic	glass,	and	[(Al	plus	1/2	Fe,	percent	
extracted	by	ammonium	oxalate)	times	60]	plus	the	volcanic	              2.	 An	irregular	decrease	in	organic-carbon	content	
glass	(percent)	is	30	or	more.                                           (Holocene	age)	between	a	depth	of	25	cm	and	either	a	depth	
                                      Vitrandic Xeropsamments            of	125	cm	below	the	mineral	soil	surface	or	a	densic,	lithic,	
                                                                         or	paralithic	contact,	whichever	is	shallower.	
LDEF.	 Other	Xeropsamments	that	have	a	horizon	within	100	                                                        Fluviwassents,	p.	142
cm	of	the	mineral	soil	surface	that	is	15	cm	or	more	thick	and	
that	either	has	20	percent	or	more	(by	volume)	durinodes	or	is	        LAF.	 Other	Wassents.	
brittle	and	has	at	least	a	firm	rupture-resistance	class	when	moist.                                            Haplowassents,	p.	143
                                       Durinodic Xeropsamments
                                                                       Fluviwassents
LDEG.	 Other	Xeropsamments	that	have	lamellae	within	200	
cm	of	the	mineral	soil	surface.                                        Key to Subgroups	
                                Lamellic Xeropsamments                 LAEA.	 Fluviwassents	that	have	a	horizon	or	horizons	with	
                                                                       a	combined	thickness	of	at	least	15	cm	within	100	cm	of	the	
LDEH.	 Other	Xeropsamments	that	have	a	base	saturation		               mineral	soil	surface	that	contain	sulfidic	materials.	
(by	NH4OAc)	of	less	than	60	percent	in	all	horizons	at	a	depth	                                                    Sulfic Fluviwassents
between	25	and	75	cm	below	the	mineral	soil	surface	or	in	the	
horizon	directly	above	a	root-limiting	layer	that	is	at	a	shallower	   LAEB.	 Other	Fluviwassents	that	have	a	lithic	contact	within	
depth.                                                                 100	cm	of	the	mineral	soil	surface.	
                                        Dystric Xeropsamments                                                  Lithic Fluviwassents	

LDEI.	 Other	Xeropsamments.                                            LAEC.	 Other	Fluviwassents	that	have	a	buried	layer	of	
                                          Typic Xeropsamments          organic	soil	materials,	20	cm	or	more	thick,	within	100	cm	of	
                                                                       the	mineral	soil	surface.	
Wassents                                                                                                 Thapto-Histic Fluviwassents	

Key to Great Groups	                                                   LAED.	 Other	Fluviwassents	that	have	a	chroma	of	3	or	more	
LAA.	 Wassents	that	have,	in	all	horizons	within	100	cm	of	            in	40	percent	or	more	of	the	matrix	of	one	or	more	horizons	
the	mineral	soil	surface,	an	electrical	conductivity	of	less	than	     between	a	depth	of	15	and	100	cm	from	the	soil	surface.	
0.2	dS/m	in	a	5:1,	by	volume,	mixture	(not	extract)	of	water	and	                                                 Aeric Fluviwassents	
soil.	
                                            Frasiwassents,	p.	142      LAEE.	 Other	Fluviwassents.	
                                                                                                                  Typic Fluviwassents
LAB.	 Other	Wassents	that	have	less	than	35	percent	(by	
volume)	rock	fragments	and	a	texture	class	of	loamy	fine	sand	         Frasiwassents	
or	coarser	in	all	layers	within	the	particle-size	control	section.	
                                                                       Key to Subgroups	
                                         Psammowassents,	p.	143
                                                                       LAAA.	 Frasiwassents	that	have,	in	all	horizons	at	a	depth	
LAC.	 Other	Wassents	that	have	a	horizon	or	horizons	with	             between	20	and	50	cm	below	the	mineral	soil	surface,	both	an	
a	combined	thickness	of	at	least	15	cm	within	50	cm	of	the	            n	value	of	more	than	0.7	and	8	percent	or	more	clay	in	the	fine-
mineral	soil	surface	that	contain	sulfidic	materials.	                 earth	fraction.	
                                            Sulfiwassents,	p.	144                                                Hydric Frasiwassents
Entisols                                                                                                                          143



LAAB. Other Frasiwassents that have a lithic contact within          Hydrowassents
100 cm of the mineral soil surface.
                                       Lithic Frasiwassents          Key to Subgroups
                                                                     LADA. Hydrowassents that have a horizon or horizons with
LAAC. Other Frasiwassents that have less than 35 percent (by         a combined thickness of at least 15 cm within 100 cm of the
volume) rock fragments and a texture class of loamy fine sand        mineral soil surface that contain sulfidic materials.
or coarser in all layers within the particle-size control section.                                               Sulfic Hydrowassents
                                      Psammentic Frasiwassents
                                                                     LADB. Other Hydrowassents that have, in all horizons at a
LAAD. Other Frasiwassents that have a buried layer of                depth between 20 and 100 cm below the mineral soil surface,
organic soil materials, 20 cm or more thick, within 100 cm of        both an n value of more than 0.7 and 8 percent or more clay in
the mineral soil surface.                                            the fine-earth fraction.
                                  Thapto-Histic Frasiwassents                                               Grossic Hydrowassents

LAAE. Other Frasiwassents that have one or both of the               LADC. Other Hydrowassents that have a lithic contact within
following:                                                           100 cm of the mineral soil surface.
   1. At a depth of 125 cm below the mineral soil surface,                                               Lithic Hydrowassents
   an organic-carbon content (Holocene age) of 0.2 percent or
   more and no densic, lithic, or paralithic contact within that     LADD. Other Hydrowassents that have a buried layer of
   depth; or                                                         organic soil materials, 20 cm or more thick, within 100 cm of
                                                                     the mineral soil surface.                                          E
                                                                                                                                        N
   2. An irregular decrease in organic-carbon content                                                 Thapto-Histic Hydrowassents       T
   (Holocene age) between a depth of 25 cm and either a depth
   of 125 cm below the mineral soil surface or a densic, lithic,     LADE. Other Hydrowassents.
   or paralithic contact, whichever is shallower.                                                             Typic Hydrowassents
                                         Fluventic Frasiwassents
                                                                     Psammowassents
LAAF. Other Frasiwassents that have a chroma of 3 or more
in 40 percent or more of the matrix of one or more horizons          Key to Subgroups
between a depth of 15 and 100 cm from the soil surface.              LABA. Psammowassents that have a horizon or horizons with
                                           Aeric Frasiwassents       a combined thickness of at least 15 cm within 100 cm of the
                                                                     mineral soil surface that contain sulfidic materials.
LAAG.      Other Frasiwassents.                                                                               Sulfic Psammowassents
                                            Typic Frasiwassents
                                                                     LABB. Other Psammowassents that have a lithic contact
Haplowassents                                                        within 100 cm of the mineral soil surface.
                                                                                                            Lithic Psammowassents
Key to Subgroups
LAFA. Haplowassents that have a horizon or horizons with             LABC. Other Psammowassents that have one or both of the
a combined thickness of at least 15 cm within 100 cm of the          following:
mineral soil surface that contain sulfidic materials.
                                                                       1. At a depth of 125 cm below the mineral soil surface,
                                            Sulfic Haplowassents
                                                                       an organic-carbon content (Holocene age) of 0.2 percent or
                                                                       more and no densic, lithic, or paralithic contact within that
LAFB. Other Haplowassents that have a lithic contact within
                                                                       depth; or
100 cm of the mineral soil surface.
                                     Lithic Haplowassents              2. An irregular decrease in organic-carbon content
                                                                       (Holocene age) between a depth of 25 cm and either a depth
LAFC. Other Haplowassents that have a chroma of 3 or more              of 125 cm below the mineral soil surface or a densic, lithic,
in 40 percent or more of the matrix of one or more horizons            or paralithic contact, whichever is shallower.
between a depth of 15 and 100 cm from the soil surface.                                                 Fluventic Psammowassents
                                          Aeric Haplowassents
                                                                     LABD. Other Psammowassents that have a chroma of 3
LAFD.      Other Haplowassents.                                      or more in 40 percent or more of the matrix of one or more
                                           Typic Haplowassents
144



horizons between a depth of 15 and 100 cm from the soil            LACD. Other Sulfiwassents that have one or both of the
surface.                                                           following:
                                      Aeric Psammowassents           1. At a depth of 125 cm below the mineral soil surface,
                                                                     an organic-carbon content (Holocene age) of 0.2 percent or
LABE. Other Psammowassents.                                          more and no densic, lithic, or paralithic contact within that
                                      Typic Psammowassents           depth; or

Sulfiwassents                                                        2. An irregular decrease in organic-carbon content
                                                                     (Holocene age) between a depth of 25 cm and either a depth
Key to Subgroups                                                     of 125 cm below the mineral soil surface or a densic, lithic,
LACA. Sulfiwassents that have a lithic contact within 100 cm         or paralithic contact, whichever is shallower.
of the mineral soil surface.                                                                               Fluventic Sulfiwassents
                                         Lithic Sulfiwassents
                                                                   LACE. Other Sulfiwassents that have a chroma of 3 or more
                                                                   in 40 percent or more of the matrix of one or more horizons
LACB. Other Sulfiwassents that have, in some horizons at a
                                                                   between a depth of 15 and 100 cm from the soil surface.
depth between 20 and 50 cm below the mineral soil surface,
                                                                                                               Aeric Sulfiwassents
either or both:
  1. An n value of 0.7 or less; or                                 LACF. Other Sulfiwassents.
                                                                                                              Typic Sulfiwassents
  2.   Less than 8 percent clay in the fine-earth fraction.
                                            Haplic Sulfiwassents

LACC. Other Sulfiwassents that have a buried layer of organic
soil materials, 20 cm or more thick, within 100 cm of the
mineral soil surface.
                                   Thapto-Histic Sulfiwassents
                                                                                                                                       145




CHAPTER 9

                                                                                                                           Gelisols

Key to Suborders                                                       of 50 cm or to a densic, lithic, or paralithic contact, whichever is
                                                                       shallower.
AA. Gelisols that have organic soil materials that meet one or                                                           Fibristels, p. 145
more of the following:
   1. Overlie cindery, fragmental, or pumiceous materials              AAD. Other Histels that have more thickness of hemic soil
   and/or fill their interstices and directly below these materials    materials than any other kind of organic soil material to a depth
   have either a densic, lithic, or paralithic contact; or             of 50 cm or to a densic, lithic, or paralithic contact, whichever is
                                                                       shallower.
   2. When added with the underlying cindery, fragmental, or
                                                                                                                         Hemistels, p. 146
   pumiceous materials, total 40 cm or more between the soil
   surface and a depth of 50 cm; or
                                                                       AAE. Other Histels.
   3. Comprise 80 percent or more, by volume, from the soil                                                             Sapristels, p. 146
   surface to a depth of 50 cm or to a glacic layer or a densic,
   lithic, or paralithic contact, whichever is shallower.              Fibristels                                                             G
                                                     Histels, p. 145                                                                          E
                                                                       Key to Subgroups                                                       L
AB. Other Gelisols that have one or more horizons showing              AACA. Fibristels that have a lithic contact within 100 cm of
cryoturbation in the form of irregular, broken, or distorted           the soil surface.
horizon boundaries, involutions, the accumulation of organic                                                         Lithic Fibristels
matter on top of the permafrost, ice or sand wedges, and
oriented rock fragments.                                               AACB. Other Fibristels that have a layer of mineral soil
                                                  Turbels, p. 150      material 30 cm or more thick within 100 cm of the soil surface.
                                                                                                                     Terric Fibristels
AC.   Other Gelisols.
                                                   Orthels, p. 146     AACC. Other Fibristels that have, within the organic soil
                                                                       materials, either one layer of mineral soil material 5 cm or more
Histels                                                                thick or two or more layers of any thickness within 100 cm of
                                                                       the soil surface.
Key to Great Groups                                                                                             Fluvaquentic Fibristels
AAA. Histels that are saturated with water for less than 30
cumulative days during normal years (and are not artificially          AACD. Other Fibristels in which three-fourths or more of the
drained).                                                              fibric soil materials are derived from Sphagnum to a depth of
                                               Folistels, p. 145       50 cm or to a densic, lithic, or paralithic contact, whichever is
                                                                       shallower.
AAB. Other Histels that are saturated with water for 30 or                                                            Sphagnic Fibristels
more cumulative days during normal years and that have both:
                                                                       AACE. Other Fibristels.
   1. A glacic layer within 100 cm of the soil surface; and                                                              Typic Fibristels
   2. Less than three-fourths (by volume) Sphagnum fibers in
   the organic soil material to a depth of 50 cm or to a densic,       Folistels
   lithic, or paralithic contact, whichever is shallower.
                                                                       Key to Subgroups
                                                  Glacistels, p. 146
                                                                       AAAA. Folistels that have a lithic contact within 50 cm of the
AAC. Other Histels that have more thickness of fibric soil             soil surface.
materials than any other kind of organic soil material to a depth                                                     Lithic Folistels
146                                                                                                            Keys to Soil Taxonomy



AAAB. Other Folistels that have a glacic layer within 100 cm         materials, either one layer of mineral soil material 5 cm or more
of the soil surface.                                                 thick or two or more layers of any thickness within 100 cm of
                                              Glacic Folistels       the soil surface.
                                                                                                              Fluvaquentic Sapristels
AAAC.     Other Folistels.
                                                  Typic Folistels    AAED. Other Sapristels.
                                                                                                                     Typic Sapristels
Glacistels
Key to Subgroups                                                     Orthels
AABA. Glacistels that have more thickness of hemic soil              Key to Great Groups
materials than any other kind of organic soil material in the
                                                                     ACA. Orthels that have, in 30 percent or more of the pedon,
upper 50 cm.
                                                                     more than 40 percent, by volume, organic soil materials from
                                               Hemic Glacistels
                                                                     the soil surface to a depth of 50 cm.
AABB. Other Glacistels that have more thickness of sapric                                                        Historthels, p. 148
soil materials than any other kind of organic soil material in the
upper 50 cm.                                                         ACB. Other Orthels that have, within 50 cm of the mineral
                                                Sapric Glacistels    soil surface, redox depletions with chroma of 2 or less and also
                                                                     aquic conditions during normal years (or artificial drainage).
AABC. Other Glacistels.                                                                                           Aquorthels, p. 147
                                                Typic Glacistels
                                                                     ACC. Other Orthels that have anhydrous conditions.
Hemistels                                                                                                    Anhyorthels, p. 146

Key to Subgroups                                                     ACD. Other Orthels that have a mollic epipedon.
AADA. Hemistels that have a lithic contact within 100 cm of                                                    Mollorthels, p. 149
the soil surface.
                                            Lithic Hemistels         ACE. Other Orthels that have an umbric epipedon.
                                                                                                             Umbrorthels, p. 150
AADB. Other Hemistels that have a layer of mineral soil
material 30 cm or more thick within 100 cm of the soil surface.      ACF. Other Orthels that have an argillic horizon within 100
                                             Terric Hemistels        cm of the mineral soil surface.
                                                                                                                Argiorthels, p. 147
AADC. Other Hemistels that have, within the organic soil
materials, either one layer of mineral soil material 5 cm or more    ACG. Other Orthels that have, below the Ap horizon or below
thick or two or more layers of any thickness within 100 cm of        a depth of 25 cm, whichever is deeper, less than 35 percent (by
the soil surface.                                                    volume) rock fragments and a texture class of loamy fine sand
                                         Fluvaquentic Hemistels      or coarser in all layers within the particle-size control section.
                                                                                                                  Psammorthels, p. 149
AADD. Other Hemistels.
                                                Typic Hemistels      ACH. Other Orthels.
                                                                                                                  Haplorthels, p. 148
Sapristels
                                                                     Anhyorthels
Key to Subgroups
                                                                     Key to Subgroups
AAEA. Sapristels that have a lithic contact within 100 cm of
the soil surface.                                                    ACCA. Anhyorthels that have a lithic contact within 50 cm of
                                             Lithic Sapristels       the mineral soil surface.
                                                                                                              Lithic Anhyorthels
AAEB. Other Sapristels that have a layer of mineral soil
material 30 cm or more thick within 100 cm of the soil surface.      ACCB. Other Anhyorthels that have a glacic layer within 100
                                             Terric Sapristels       cm of the mineral soil surface.
                                                                                                             Glacic Anhyorthels
AAEC.     Other Sapristels that have, within the organic soil
Gelisols                                                                                                                            147




ACCC. Other Anhyorthels that have a petrogypsic horizon               and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling
within 100 cm of the mineral soil surface.                            more than 1.0.
                                       Petrogypsic Anhyorthels                                                   Andic Aquorthels

ACCD. Other Anhyorthels that have a gypsic horizon within             ACBF. Other Aquorthels that have, throughout one or more
100 cm of the mineral soil surface.                                   horizons with a total thickness of 18 cm or more within 75 cm
                                       Gypsic Anhyorthels             of the mineral soil surface, one or both of the following:
                                                                         1. More than 35 percent (by volume) fragments coarser
ACCE. Other Anhyorthels that have a horizon 15 cm or more                than 2.0 mm, of which more than 66 percent is cinders,
thick that contains 12 cmol(-)/L nitrate in a 1:5 soil:water             pumice, and pumicelike fragments; or
extract and in which the product of its thickness (in cm) and its
nitrate concentration is 3,500 or more.                                  2. A fine-earth fraction containing 30 percent or more
                                               Nitric Anhyorthels        particles 0.02 to 2.0 mm in diameter; and
                                                                            a. In the 0.02 to 2.0 mm fraction, 5 percent or more
ACCF. Other Anhyorthels that have a salic horizon within 100                volcanic glass; and
cm of the mineral soil surface.
                                           Salic Anhyorthels                b. [(Al plus 1/2 Fe, percent extracted by ammonium
                                                                            oxalate) times 60] plus the volcanic glass (percent) is
ACCG. Other Anhyorthels that have a calcic horizon within                   equal to 30 or more.
100 cm of the mineral soil surface.                                                                              Vitrandic Aquorthels
                                        Calcic Anhyorthels
                                                                      ACBG. Other Aquorthels that have a salic horizon within 100
ACCH.      Other Anhyorthels.                                         cm of the mineral soil surface.
                                                Typic Anhyorthels                                                Salic Aquorthels          G
                                                                                                                                           E
                                                                                                                                           L
Aquorthels                                                            ACBH. Other Aquorthels that have less than 35 percent (by
                                                                      volume) rock fragments and a texture class of loamy fine sand
Key to Subgroups                                                      or coarser in all layers within the particle-size control section.
ACBA. Aquorthels that have a lithic contact within 50 cm of                                                     Psammentic Aquorthels
the mineral soil surface.
                                           Lithic Aquorthels          ACBI. Other Aquorthels that have a slope of less than 25
                                                                      percent and one or both of the following:
ACBB. Other Aquorthels that have a glacic layer within 100               1. At a depth of 125 cm below the mineral soil surface,
cm of the mineral soil surface.                                          an organic-carbon content (Holocene age) of 0.2 percent or
                                         Glacic Aquorthels               more and no densic, lithic, or paralithic contact within that
                                                                         depth; or
ACBC. Other Aquorthels that have a sulfuric horizon or
sulfidic materials within 100 cm of the mineral soil surface.            2. An irregular decrease in organic-carbon content
                                           Sulfuric Aquorthels           (Holocene age) between a depth of 25 cm and either a depth
                                                                         of 125 cm below the mineral soil surface or a densic, lithic,
ACBD.      Other Aquorthels that have either:                            or paralithic contact, whichever is shallower.
                                                                                                              Fluvaquentic Aquorthels
   1. Organic soil materials that are discontinuous at the
   surface; or                                                        ACBJ.    Other Aquorthels.
   2. Organic soil materials at the surface that change in                                                           Typic Aquorthels
   thickness fourfold or more within a pedon.
                                      Ruptic-Histic Aquorthels        Argiorthels
                                                                      Key to Subgroups
ACBE. Other Aquorthels that have, throughout one or more
horizons with a total thickness of 18 cm or more within 75 cm         ACFA. Argiorthels that have a lithic contact within 50 cm of
of the mineral soil surface, a fine-earth fraction with both a bulk   the mineral soil surface.
density of 1.0 g/cm3 or less, measured at 33 kPa water retention,                                                 Lithic Argiorthels
148	                                                                                                              Keys	to	Soil	Taxonomy



ACFB.	 Other	Argiorthels	that	have	a	glacic	layer	within	100	             more	and	no	densic,	lithic,	or	paralithic	contact	within	that	
cm	of	the	mineral	soil	surface.                                           depth;	or
                                           Glacic Argiorthels
                                                                          2.	 An	irregular	decrease	in	organic-carbon	content	
                                                                          (Holocene	age)	between	a	depth	of	25	cm	and	either	a	depth	
ACFC.	 Other	Argiorthels	that	have	a	natric	horizon.
                                                                          of	125	cm	below	the	mineral	soil	surface	or	a	densic,	lithic,	
                                           Natric Argiorthels
                                                                          or	paralithic	contact,	whichever	is	shallower.
                                                                                                                  Fluventic Haplorthels
ACFD.	 Other	Argiorthels.
                                                 Typic Argiorthels
                                                                        ACHG.	 Other	Haplorthels.
                                                                                                                      Typic Haplorthels
Haplorthels
Key to Subgroups                                                        Historthels
ACHA.	 Haplorthels	that	have	a	lithic	contact	within	50	cm	of	          Key to Subgroups
the	mineral	soil	surface.
                                                                        ACAA.	 Historthels	that	have	a	lithic	contact	within	50	cm	of	
                                           Lithic Haplorthels
                                                                        the	soil	surface.
                                                                                                                    Lithic Historthels
ACHB.	 Other	Haplorthels	that	have	a	glacic	layer	within	100	
cm	of	the	mineral	soil	surface.
                                                                        ACAB.	 Other	Historthels	that	have	a	glacic	layer	within	100	
                                          Glacic Haplorthels
                                                                        cm	of	the	soil	surface.
                                                                                                                   Glacic Historthels
ACHC.	 Other	Haplorthels	that	have	a	slope	of	less	than	25	
percent;	and
                                                                        ACAC.	 Other	Historthels	that	have	a	slope	of	less	than	25	
  1.	 In	one	or	more	horizons	within	75	cm	of	the	mineral	soil	         percent;	and
  surface,	redox	depletions	with	chroma	of	2	or	less	and	also	
                                                                          1.	 In	one	or	more	horizons	within	75	cm	of	the	mineral	soil	
  aquic	conditions	for	some	time	in	normal	years	(or	artificial	
                                                                          surface,	redox	depletions	with	chroma	of	2	or	less	and	also	
  drainage);	and
                                                                          aquic	conditions	for	some	time	in	normal	years	(or	artificial	
  2.	 One or both of	the	following:                                       drainage);	and
       a.	 At	a	depth	of	125	cm	below	the	mineral	soil	surface,	          	2.	 One or both of	the	following:
       an	organic-carbon	content	(Holocene	age)	of	0.2	percent	
                                                                             a.	 At	a	depth	of	125	cm	below	the	mineral	soil	surface,	
       or	more	and	no	densic,	lithic,	or	paralithic	contact	within	
                                                                             an	organic-carbon	content	(Holocene	age)	of	0.2	percent	
       that	depth;	or
                                                                             or	more	and	no	densic,	lithic,	or	paralithic	contact	within	
       b.	 An	irregular	decrease	in	organic-carbon	content	                  that	depth;	or
       (Holocene	age)	between	a	depth	of	25	cm	and	either	
                                                                             b.	 An	irregular	decrease	in	organic-carbon	content	
       a	depth	of	125	cm	below	the	mineral	soil	surface	or	a	
                                                                             (Holocene	age)	between	a	depth	of	25	cm	and	either	
       densic,	lithic,	or	paralithic	contact,	whichever	is	shallower.
                                                                             a	depth	of	125	cm	below	the	mineral	soil	surface	or	a	
                                         Fluvaquentic Haplorthels
                                                                             densic,	lithic,	or	paralithic	contact,	whichever	is	shallower.
                                                                                                               	Fluvaquentic Historthels
ACHD.	 Other	Haplorthels	that	have	a	folistic	epipedon.
                                         Folistic Haplorthels
                                                                        ACAD.	 Other	Historthels	that	have	a	slope	of	less	than	25	
                                                                        percent	and	one or both of	the	following:
ACHE.	 Other	Haplorthels	that	have,	in	one	or	more	horizons	
within	75	cm	of	the	mineral	soil	surface,	redox	depletions	with	          1.	 At	a	depth	of	125	cm	below	the	mineral	soil	surface,	
chroma	of	2	or	less	and	also	aquic	conditions	for	some	time	              an	organic-carbon	content	(Holocene	age)	of	0.2	percent	or	
during	normal	years	(or	artificial	drainage).                             more	and	no	densic,	lithic,	or	paralithic	contact	within	that	
                                              Aquic Haplorthels           depth;	or
                                                                          2.	 An	irregular	decrease	in	organic-carbon	content	
ACHF.	 Other	Haplorthels	that	have	a	slope	of	less	than	25	
                                                                          (Holocene	age)	between	a	depth	of	25	cm	and	either	a	depth	
percent	and	one or both of	the	following:
                                                                          of	125	cm	below	the	mineral	soil	surface	or	a	densic,	lithic,	
  1.	 At	a	depth	of	125	cm	below	the	mineral	soil	surface,	               or	paralithic	contact,	whichever	is	shallower.
  an	organic-carbon	content	(Holocene	age)	of	0.2	percent	or	                                                      Fluventic Historthels
Gelisols	                                                                                                                              149



ACAE.	 Other	Historthels	that	have	more	than	40	percent,	by	                 b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
volume,	organic	soil	materials	from	the	soil	surface	to	a	depth	             oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
of	50	cm	in	75	percent	or	less	of	the	pedon.                                 equal	to	30	or	more.
                                              Ruptic Historthels                                                  Vitrandic Mollorthels

ACAF.	 Other	Historthels.                                              ACDF.	 Other	Mollorthels	that	have	a	folistic	epipedon.
                                                Typic Historthels                                                Folistic Mollorthels

Mollorthels                                                            ACDG.	 Other	Mollorthels	that	have	both:
Key to Subgroups                                                          1.	 A	mollic	epipedon	that	is	40	cm	or	more	thick	with	a	
ACDA.	 Mollorthels	that	have	a	lithic	contact	within	50	cm	of	            texture	class	finer	than	loamy	fine	sand;	and
the	mineral	soil	surface.                                                 2.	 A	slope	of	less	than	25	percent.
                                           Lithic Mollorthels                                                     Cumulic Mollorthels
ACDB.	 Other	Mollorthels	that	have	a	glacic	layer	within	100	
                                                                       ACDH.	 Other	Mollorthels	that	have,	in	one	or	more	horizons	
cm	of	the	mineral	soil	surface.
                                                                       within	100	cm	of	the	mineral	soil	surface,	distinct	or	prominent	
                                          Glacic Mollorthels
                                                                       redox	concentrations	and	also	aquic	conditions	for	some	time	
                                                                       during	normal	years	(or	artificial	drainage).
ACDC.	 Other	Mollorthels	that	have	one or both	of	the	
                                                                                                                     Aquic Mollorthels
following:
   1.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	are	      ACDI.	 Other	Mollorthels.
   5	mm	or	more	wide	through	a	thickness	of	30	cm	or	more	for	                                                       Typic Mollorthels
   some	time	during	normal	years	and	slickensides	or	wedge-                                                                                  G
                                                                                                                                             E
   shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	      Psammorthels                                                          L
   boundary	within	125	cm	of	the	mineral	soil	surface;	or
                                                                       Key to Subgroups
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	
   mineral	soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	     ACGA.	 Psammorthels	that	have	a	lithic	contact	within	50	cm	
   lithic,	or	paralithic	contact,	whichever	is	shallower.              of	the	mineral	soil	surface.
                                                Vertic Mollorthels                                            Lithic Psammorthels

ACDD.	 Other	Mollorthels	that	have,	throughout	one	or	more	            ACGB.	 Other	Psammorthels	that	have	a	glacic	layer	within	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	         100	cm	of	the	mineral	soil	surface.
of	the	mineral	soil	surface,	a	fine-earth	fraction	with	both	a	bulk	                                        Glacic Psammorthels
density	of	1.0	g/cm3	or	less,	measured	at	33	kPa	water	retention,	
and	Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	totaling	         ACGC.	 Other	Psammorthels	that	have	a	horizon	5	cm	or	more	
more	than	1.0.                                                         thick	that	has	one or more	of	the	following:
                                                Andic Mollorthels
                                                                          1.	 In	25	percent	or	more	of	each	pedon,	cementation	by	
                                                                          organic	matter	and	aluminum,	with	or	without	iron;	or
ACDE.	 Other	Mollorthels	that	have,	throughout	one	or	more	               2.	 Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	            totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	
of	the	mineral	soil	surface,	one or both	of	the	following:                overlying	horizon;	or
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	                3.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	                high	or	lower	in	an	overlying	horizon.
   pumice,	and	pumicelike	fragments;	or                                                                          Spodic Psammorthels
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	
   particles	0.02	to	2.0	mm	in	diameter;	and                           ACGD.	 Other	Psammorthels.
                                                                                                                  Typic Psammorthels
      a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	
      volcanic	glass;	and
150	                                                                                                             Keys	to	Soil	Taxonomy



Umbrorthels                                                               1.	 An	umbric	epipedon	that	is	40	cm	or	more	thick	with	a	
                                                                          texture	class	finer	than	loamy	fine	sand;	and
Key to Subgroups
                                                                          2.	 A	slope	of	less	than	25	percent.
ACEA.	 Umbrorthels	that	have	a	lithic	contact	within	50	cm	of	                                                   Cumulic Umbrorthels
the	mineral	soil	surface.
                                         Lithic Umbrorthels            ACEH.	 Other	Umbrorthels	that	have,	in	one	or	more	horizons	
                                                                       within	100	cm	of	the	mineral	soil	surface,	distinct	or	prominent	
ACEB.	 Other	Umbrorthels	that	have	a	glacic	layer	within	100	          redox	concentrations	and	also	aquic	conditions	for	some	time	
cm	of	the	mineral	soil	surface.                                        during	normal	years	(or	artificial	drainage).
                                        Glacic Umbrorthels                                                           Aquic Umbrorthels
ACEC.	 Other	Umbrorthels	that	have	one or both	of	the	                 ACEI.	 Other	Umbrorthels.
following:                                                                                                         Typic Umbrorthels
   1.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	are	
   5	mm	or	more	wide	through	a	thickness	of	30	cm	or	more	for	         Turbels
   some	time	during	normal	years	and	slickensides	or	wedge-
   shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	      Key to Great Groups
   boundary	within	125	cm	of	the	mineral	soil	surface;	or              ABA.	 Turbels	that	have,	in	30	percent	or	more	of	the	pedon,	
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	           more	than	40	percent,	by	volume,	organic	soil	materials	from	
   mineral	soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	     the	soil	surface	to	a	depth	of	50	cm.
   lithic,	or	paralithic	contact,	whichever	is	shallower.                                                        Histoturbels,	p.	151
                                               Vertic Umbrorthels
                                                                       ABB.	 Other	Turbels	that	have,	within	50	cm	of	the	mineral	
ACED.	 Other	Umbrorthels	that	have,	throughout	one	or	more	            soil	surface,	redox	depletions	with	chroma	of	2	or	less	and	also	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	         aquic	conditions	during	normal	years	(or	artificial	drainage).
of	the	mineral	soil	surface,	a	fine-earth	fraction	with	both	a	bulk	                                               Aquiturbels,	p.	151
density	of	1.0	g/cm3	or	less,	measured	at	33	kPa	water	retention,	
and	Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	totaling	         ABC.	 Other	Turbels	that	have	anhydrous	conditions.
more	than	1.0.                                                                                                  Anhyturbels,	p.	150
                                               Andic Umbrorthels
                                                                       ABD.	 Other	Turbels	that	have	a	mollic	epipedon.
ACEE.	 Other	Umbrorthels	that	have,	throughout	one	or	more	                                                      Molliturbels,	p.	152
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
of	the	mineral	soil	surface,	one or both	of	the	following:             ABE.	 Other	Turbels	that	have	an	umbric	epipedon.
                                                                                                               Umbriturbels,	p.	152
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	             ABF.	 Other	Turbels	that	have	less	than	35	percent	(by	volume)	
   pumice,	and	pumicelike	fragments;	or                                rock	fragments	and	a	texture	class	of	loamy	fine	sand	or	coarser	
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	            in	all	layers	within	the	particle-size	control	section.
   particles	0.02	to	2.0	mm	in	diameter; and                                                                      Psammoturbels,	p.	152
       a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	          ABG.	 Other	Turbels.
       volcanic	glass; and                                                                                        Haploturbels,	p.	151
       b.	 [(Al	plus	 /2	Fe,	percent	extracted	by	ammonium	
                    1

       oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	        Anhyturbels
       equal	to	30	or	more.
                                                                       Key to Subgroups
                                           Vitrandic Umbrorthels
                                                                       ABCA.	 Anhyturbels	that	have	a	lithic	contact	within	50	cm	of	
ACEF.	 Other	Umbrorthels	that	have	a	folistic	epipedon.                the	mineral	soil	surface.
                                       Folistic Umbrorthels                                                      Lithic Anhyturbels

ACEG.	 Other	Umbrorthels	that	have	both:
Gelisols	                                                                                                                          151



ABCB.	 Other	Anhyturbels	that	have	a	glacic	layer	within	100	        ABBE.	 Other	Aquiturbels	that	have	less	than	35	percent	(by	
cm	of	the	mineral	soil	surface.                                      volume)	rock	fragments	and	a	texture	class	of	loamy	fine	sand	
                                         Glacic Anhyturbels          or	coarser	in	all	layers	within	the	particle-size	control	section.
                                                                                                              Psammentic Aquiturbels
ABCC.	 Other	Anhyturbels	that	have	a	petrogypsic	horizon	
within	100	cm	of	the	mineral	soil	surface.                           ABBF.	 Other	Aquiturbels.
                                      Petrogypsic Anhyturbels                                                      Typic Aquiturbels

ABCD.	 Other	Anhyturbels	that	have	a	gypsic	horizon	within	          Haploturbels
100	cm	of	the	mineral	soil	surface.
                                       Gypsic Anhyturbels            Key to Subgroups
                                                                     ABGA.	 Haploturbels	that	have	a	lithic	contact	within	50	cm	
ABCE.	 Other	Anhyturbels	that	have	a	horizon	15	cm	or	               of	the	mineral	soil	surface.
more	thick	that	contains	12	cmol(-)/L	nitrate	in	a	1:5	soil:water	                                            Lithic Haploturbels
extract	and	in	which	the	product	of	its	thickness	(in	cm)	and	its	
nitrate	concentration	is	3,500	or	more.
                                                                     ABGB.	 Other	Haploturbels	that	have	a	glacic	layer	within	100	
                                              Nitric Anhyturbels
                                                                     cm	of	the	mineral	soil	surface.
                                                                                                             Glacic Haploturbels
ABCF.	 Other	Anhyturbels	that	have	a	salic	horizon	within	100	
cm	of	the	mineral	soil	surface.
                                                                     ABGC.	 Other	Haploturbels	that	have	a	folistic	epipedon.
                                           Salic Anhyturbels
                                                                                                            Folistic Haploturbels
ABCG.	 Other	Anhyturbels	that	have	a	calcic	horizon	within	
                                                                     ABGD.	 Other	Haploturbels	that	have,	in	one	or	more	horizons	
100	cm	of	the	mineral	soil	surface.                                                                                                       G
                                                                     within	100	cm	of	the	mineral	soil	surface,	distinct	or	prominent	    E
                                         Calcic Anhyturbels                                                                               L
                                                                     redox	concentrations	and	also	aquic	conditions	for	some	time	
                                                                     during	normal	years	(or	artificial	drainage).
ABCH.	 Other	Anhyturbels.
                                                                                                                   Aquic Haploturbels
                                             Typic Anhyturbels

                                                                     ABGE.	 Other	Haploturbels.
Aquiturbels                                                                                                      Typic Haploturbels
Key to Subgroups
ABBA.	 Aquiturbels	that	have	a	lithic	contact	within	50	cm	of	       Histoturbels
the	mineral	soil	surface.                                            Key to Subgroups
                                           Lithic Aquiturbels
                                                                     ABAA.	 Histoturbels	that	have	a	lithic	contact	within	50	cm	of	
ABBB.	 Other	Aquiturbels	that	have	a	glacic	layer	within	100	        the	soil	surface.
cm	of	the	mineral	soil	surface.                                                                                 Lithic Histoturbels
                                          Glacic Aquiturbels
                                                                     ABAB.	 Other	Histoturbels	that	have	a	glacic	layer	within	100	
ABBC.	 Other	Aquiturbels	that	have	a	sulfuric	horizon	or	            cm	of	the	soil	surface.
sulfidic	materials	within	100	cm	of	the	mineral	soil	surface.                                                 Glacic Histoturbels
                                           Sulfuric Aquiturbels
                                                                     ABAC.	 Other	Histoturbels	that	have	more	than	40	percent,	by	
ABBD.	 Other	Aquiturbels	that	have	either:                           volume,	organic	soil	materials	from	the	soil	surface	to	a	depth	
                                                                     of	50	cm	in	75	percent	or	less	of	the	pedon.
   1.	 Organic	soil	materials	that	are	discontinuous	at	the	
                                                                                                                  Ruptic Histoturbels
   surface;	or
   2.	 Organic	soil	materials	at	the	surface	that	change	in	         ABAD.	 Other	Histoturbels.
   thickness	fourfold	or	more	within	a	pedon.                                                                     Typic Histoturbels
                                      Ruptic-Histic Aquiturbels
152	                                                                                                             Keys	to	Soil	Taxonomy



Molliturbels                                                              1.	 A	mollic	epipedon	that	is	40	cm	or	more	thick	with	a	
                                                                          texture	class	finer	than	loamy	fine	sand;	and
Key to Subgroups
                                                                          2.	 A	slope	of	less	than	25	percent.
ABDA.	 Molliturbels	that	have	a	lithic	contact	within	50	cm	of	                                                  Cumulic Molliturbels
the	mineral	soil	surface.
                                           Lithic Molliturbels         ABDH.	 Other	Molliturbels	that	have,	in	one	or	more	horizons	
                                                                       within	100	cm	of	the	mineral	soil	surface,	distinct	or	prominent	
ABDB.	 Other	Molliturbels	that	have	a	glacic	layer	within	100	         redox	concentrations	and	also	aquic	conditions	for	some	time	
cm	of	the	mineral	soil	surface.                                        during	normal	years	(or	artificial	drainage).
                                         Glacic Molliturbels                                                         Aquic Molliturbels

ABDC.	 Other	Molliturbels	that	have	one or both	of	the	                ABDI.	 Other	Molliturbels.
following:                                                                                                          Typic Molliturbels
   1.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	are	
   5	mm	or	more	wide	through	a	thickness	of	30	cm	or	more	for	         Psammoturbels
   some	time	during	normal	years	and	slickensides	or	wedge-            Key to Subgroups
   shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	
                                                                       ABFA.	 Psammoturbels	that	have	a	lithic	contact	within	50	cm	
   boundary	within	125	cm	of	the	mineral	soil	surface;	or
                                                                       of	the	mineral	soil	surface.
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	                                                 Lithic Psammoturbels
   mineral	soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	
   lithic,	or	paralithic	contact,	whichever	is	shallower.              ABFB.	 Other	Psammoturbels	that	have	a	glacic	layer	within	
                                               Vertic Molliturbels     100	cm	of	the	mineral	soil	surface.
                                                                                                           Glacic Psammoturbels
ABDD.	 Other	Molliturbels	that	have,	throughout	one	or	more	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	         ABFC.	 Other	Psammoturbels	that	have	a	horizon	5	cm	or	
of	the	mineral	soil	surface,	a	fine-earth	fraction	with	both	a	bulk	   more	thick	that	has	one or more	of	the	following:
density	of	1.0	g/cm3	or	less,	measured	at	33	kPa	water	retention,	        1.	 In	25	percent	or	more	of	each	pedon,	cementation	by	
and	Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	totaling	            organic	matter	and	aluminum,	with	or	without	iron;	or
more	than	1.0.
                                               Andic Molliturbels         2.	 Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	
                                                                          totaling	0.25	or	more,	and	half	that	amount	or	less	in	an	
ABDE.	 Other	Molliturbels	that	have,	throughout	one	or	more	              overlying	horizon;	or
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	            3.	 An	ODOE	value	of	0.12	or	more,	and	a	value	half	as	
of	the	mineral	soil	surface,	one or both	of	the	following:                high	or	lower	in	an	overlying	horizon.
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	                                                     Spodic Psammoturbels
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	
   pumice,	and	pumicelike	fragments;	or                                ABFD.	 Other	Psammoturbels.
                                                                                                                 Typic Psammoturbels
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	
   particles	0.02	to	2.0	mm	in	diameter; and                           Umbriturbels
       a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	          Key to Subgroups
       volcanic	glass; and
                                                                       ABEA.	 Umbriturbels	that	have	a	lithic	contact	within	50	cm	
       b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	            of	the	mineral	soil	surface.
       oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	                                                 Lithic Umbriturbels
       equal	to	30	or	more.
                                           Vitrandic Molliturbels      ABEB.	 Other	Umbriturbels	that	have	a	glacic	layer	within	100	
                                                                       cm	of	the	mineral	soil	surface.
ABDF.	 Other	Molliturbels	that	have	a	folistic	epipedon.                                                      Glacic Umbriturbels
                                         Folistic Molliturbels
                                                                       ABEC.	 Other	Umbriturbels	that	have	one or both	of	the	
ABDG.	 Other	Molliturbels	that	have	both:                              following:
Gelisols	                                                                                                                             153



   1.	 Cracks	within	125	cm	of	the	mineral	soil	surface	that	are	            a.	 In	the	0.02	to	2.0	mm	fraction,	5	percent	or	more	
   5	mm	or	more	wide	through	a	thickness	of	30	cm	or	more	for	               volcanic	glass; and
   some	time	during	normal	years	and	slickensides	or	wedge-
                                                                             b.	 [(Al	plus	1/2	Fe,	percent	extracted	by	ammonium	
   shaped	peds	in	a	layer	15	cm	or	more	thick	that	has	its	upper	
                                                                             oxalate)	times	60]	plus	the	volcanic	glass	(percent)	is	
   boundary	within	125	cm	of	the	mineral	soil	surface;	or
                                                                             equal	to	30	or	more.
   2.	 A	linear	extensibility	of	6.0	cm	or	more	between	the	                                                    Vitrandic Umbriturbels
   mineral	soil	surface	and	either	a	depth	of	100	cm	or	a	densic,	
   lithic,	or	paralithic	contact,	whichever	is	shallower.
                                                                       ABEF.	 Other	Umbriturbels	that	have	a	folistic	epipedon.
                                              Vertic Umbriturbels
                                                                                                              Folistic Umbriturbels
ABED.	 Other	Umbriturbels	that	have,	throughout	one	or	more	
                                                                       ABEG.	 Other	Umbriturbels	that	have	both:
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
of	the	mineral	soil	surface,	a	fine-earth	fraction	with	both	a	bulk	      1.	 An	umbric	epipedon	that	is	40	cm	or	more	thick	with	a	
density	of	1.0	g/cm3	or	less,	measured	at	33	kPa	water	retention,	        texture	class	finer	than	loamy	fine	sand;	and
and	Al	plus	1/2	Fe	percentages	(by	ammonium	oxalate)	totaling	
                                                                          2.	 A	slope	of	less	than	25	percent.
more	than	1.0.
                                                                                                                 Cumulic Umbriturbels
                                              Andic Umbriturbels
                                                                       ABEH.	 Other	Umbriturbels	that	have,	in	one	or	more	horizons	
ABEE.	 Other	Umbriturbels	that	have,	throughout	one	or	more	
                                                                       within	100	cm	of	the	mineral	soil	surface,	distinct	or	prominent	
horizons	with	a	total	thickness	of	18	cm	or	more	within	75	cm	
                                                                       redox	concentrations	and	also	aquic	conditions	for	some	time	
of	the	mineral	soil	surface,	one or both	of	the	following:
                                                                       during	normal	years	(or	artificial	drainage).
   1.	 More	than	35	percent	(by	volume)	fragments	coarser	                                                         Aquic Umbriturbels
   than	2.0	mm,	of	which	more	than	66	percent	is	cinders,	                                                                                  G
   pumice,	and	pumicelike	fragments;	or                                ABEI.	 Other	Umbriturbels.                                           E
                                                                                                                                            L
                                                                                                                   Typic Umbriturbels
   2.	 A	fine-earth	fraction	containing	30	percent	or	more	
   particles	0.02	to	2.0	mm	in	diameter; and
                                                                                                                                      155




CHAPTER 10

                                                                                                                        Histosols

Key to Suborders                                                      Fibrists
BA. Histosols that are saturated with water for less than 30          Key to Great Groups
cumulative days during normal years (and are not artificially
drained).                                                             BCA. Fibrists that have a cryic soil temperature regime.
                                                 Folists, p. 156                                                 Cryofibrists, p. 155

BB. Other Histosols that have a positive water potential at the       BCB. Other Fibrists in which fibric Sphagnum constitutes
soil surface for more than 21 hours of each day in all years.         three-fourths or more of the volume to either a depth of 90 cm
                                                Wassists, p. 159      from the soil surface or to a densic, lithic, or paralithic contact,
                                                                      fragmental materials, or other mineral soil materials if at a depth
BC. Other Histosols that:                                             of less than 90 cm.
                                                                                                                 Sphagnofibrists, p. 156
   1. Have more thickness of fibric soil materials than any
   other kind of organic soil materials either:                       BCC. Other Fibrists.
                                                                                                                   Haplofibrists, p. 156
      a. In the organic parts of the subsurface tier if there is no
      continuous layer of mineral soil material 40 cm or more
      thick that has its upper boundary within the subsurface         Cryofibrists                                                           H
                                                                                                                                             I
      tier; or                                                        Key to Subgroups                                                       S

      b. In the combined thickness of the organic parts of the        BCAA. Cryofibrists that have a layer of water within the
      surface and subsurface tiers and there is a continuous          control section, below the surface tier.
      layer of mineral soil material 40 cm or more thick that has                                              Hydric Cryofibrists
      its upper boundary within the subsurface tier; and
                                                                      BCAB. Other Cryofibrists that have a lithic contact at the
   2. Do not have a sulfuric horizon within 50 cm of the soil
                                                                      lower boundary of the control section.
   surface; and
                                                                                                                 Lithic Cryofibrists
   3. Do not have sulfidic materials within 100 cm of the soil
   surface.                                                           BCAC. Other Cryofibrists that have a layer of mineral soil
                                               Fibrists, p. 155       material 30 cm or more thick that has its upper boundary within
                                                                      the control section, below the surface tier.
BD. Other Histosols that have more thickness of sapric soil                                                        Terric Cryofibrists
materials than any other kind of organic soil materials either:
                                                                      BCAD. Other Cryofibrists that have, within the organic soil
   1. In the organic parts of the subsurface tier if there is no      materials, either one layer of mineral soil material 5 cm or
   continuous layer of mineral soil material 40 cm or more thick      more thick or two or more layers of mineral soil material of any
   that has its upper boundary within the subsurface tier; or         thickness in the control section, below the surface tier.
   2. In the combined thickness of the organic parts of the                                                  Fluvaquentic Cryofibrists
   surface and subsurface tiers and there is a continuous layer
   of mineral soil material 40 cm or more thick that has its          BCAE. Other Cryofibrists in which three-fourths or more of
   upper boundary within the subsurface tier.                         the fiber volume in the surface tier is derived from Sphagnum.
                                                  Saprists, p. 158                                                Sphagnic Cryofibrists

BE. Other Histosols.                                                  BCAF. Other Cryofibrists.
                                                  Hemists, p. 157                                                    Typic Cryofibrists
156                                                                                                          Keys to Soil Taxonomy



Haplofibrists                                                       BCBE. Other Sphagnofibrists that have, within the organic
                                                                    soil materials, either one layer of mineral soil material 5 cm or
Key to Subgroups                                                    more thick or two or more layers of mineral soil material of any
BCCA. Haplofibrists that have a layer of water within the           thickness in the control section, below the surface tier.
control section, below the surface tier.                                                                Fluvaquentic Sphagnofibrists
                                         Hydric Haplofibrists
                                                                    BCBF. Other Sphagnofibrists that have one or more layers of
BCCB. Other Haplofibrists that have a lithic contact at the         hemic and sapric materials with a total thickness of 25 cm or
lower boundary of the control section.                              more in the control section, below the surface tier.
                                         Lithic Haplofibrists                                                Hemic Sphagnofibrists

BCCC. Other Haplofibrists that have one or more limnic              BCBG. Other Sphagnofibrists.
layers with a total thickness of 5 cm or more within the control                                             Typic Sphagnofibrists
section.
                                           Limnic Haplofibrists
                                                                    Folists
BCCD. Other Haplofibrists that have a layer of mineral soil         Key to Great Groups
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.                        BAA. Folists that have a cryic soil temperature regime.
                                             Terric Haplofibrists                                               Cryofolists, p. 156

BCCE. Other Haplofibrists that have, within the organic soil        BAB. Other Folists that have an aridic (or torric) soil moisture
materials, either one layer of mineral soil material 5 cm or        regime.
more thick or two or more layers of mineral soil material of any                                                Torrifolists, p. 156
thickness in the control section, below the surface tier.
                                      Fluvaquentic Haplofibrists    BAC. Other Folists that have an ustic or xeric soil moisture
                                                                    regime.
BCCF. Other Haplofibrists that have one or more layers of                                                        Ustifolists, p. 157
hemic and sapric materials with a total thickness of 25 cm or
more in the control section, below the surface tier.                BAD.    Other Folists.
                                            Hemic Haplofibrists                                                    Udifolists, p. 157

BCCG.     Other Haplofibrists.                                      Cryofolists
                                            Typic Haplofibrists
                                                                    Key to Subgroups
Sphagnofibrists
                                                                    BAAA. Cryofolists that have a lithic contact within 50 cm of
Key to Subgroups                                                    the soil surface.
BCBA. Sphagnofibrists that have a layer of water within the                                                     Lithic Cryofolists
control section, below the surface tier.
                                         Hydric Sphagnofibrists     BAAB. Other Cryofolists.
                                                                                                                  Typic Cryofolists
BCBB. Other Sphagnofibrists that have a lithic contact at the
lower boundary of the control section.                              Torrifolists
                                       Lithic Sphagnofibrists       Key to Subgroups
BCBC. Other Sphagnofibrists that have one or more limnic            BABA. Torrifolists that have a lithic contact within 50 cm of
layers with a total thickness of 5 cm or more within the control    the soil surface.
section.                                                                                                         Lithic Torrifolists
                                         Limnic Sphagnofibrists
                                                                    BABB. Other Torrifolists.
BCBD. Other Sphagnofibrists that have a layer of mineral soil                                                     Typic Torrifolists
material 30 cm or more thick that has its upper boundary within
the control section, below the surface tier.
                                          Terric Sphagnofibrists
Histosols                                                                                                                       157



Udifolists                                                         BEDC. Other Cryohemists that have a layer of mineral soil
                                                                   material 30 cm or more thick that has its upper boundary within
Key to Subgroups                                                   the control section, below the surface tier.
BADA. Udifolists that have a lithic contact within 50 cm of                                                     Terric Cryohemists
the soil surface.
                                             Lithic Udifolists     BEDD. Other Cryohemists that have, within the organic soil
                                                                   materials, either one layer of mineral soil material 5 cm or
BADB.       Other Udifolists.                                      more thick or two or more layers of mineral soil material of any
                                               Typic Udifolists    thickness in the control section, below the surface tier.
                                                                                                         Fluvaquentic Cryohemists
Ustifolists
                                                                   BEDE. Other Cryohemists.
Key to Subgroups                                                                                               Typic Cryohemists
BACA. Ustifolists that have a lithic contact within 50 cm of
the soil surface.                                                  Haplohemists
                                              Lithic Ustifolists   Key to Subgroups
BACB.       Other Ustifolists.                                     BEEA. Haplohemists that have a layer of water within the
                                               Typic Ustifolists   control section, below the surface tier.
                                                                                                            Hydric Haplohemists
Hemists                                                            BEEB. Other Haplohemists that have a lithic contact at the
Key to Great Groups                                                lower boundary of the control section.
                                                                                                          Lithic Haplohemists
BEA. Hemists that have a sulfuric horizon within 50 cm of the
soil surface.                                                      BEEC. Other Haplohemists that have one or more limnic
                                        Sulfohemists, p. 158       layers with a total thickness of 5 cm or more within the control    H
                                                                   section.                                                            I
                                                                                                                                       S
BEB. Other Hemists that have sulfidic materials within 100                                                   Limnic Haplohemists
cm of the soil surface.
                                         Sulfihemists, p. 158      BEED. Other Haplohemists that have a layer of mineral soil
                                                                   material 30 cm or more thick that has its upper boundary within
BEC. Other Hemists that have a horizon 2 cm or more thick          the control section, below the surface tier.
in which humilluvic materials constitute one-half or more of the                                                Terric Haplohemists
volume.
                                            Luvihemists, p. 158    BEEE. Other Haplohemists that have, within the organic
                                                                   soil materials, either one layer of mineral soil material 5 cm or
BED.    Other Hemists that have a cryic soil temperature regime.   more thick or two or more layers of mineral soil material of any
                                            Cryohemists, p. 157    thickness in the control section, below the surface tier.
                                                                                                        Fluvaquentic Haplohemists
BEE. Other Hemists.
                                          Haplohemists, p. 157     BEEF. Other Haplohemists that have one or more layers of
                                                                   fibric materials with a total thickness of 25 cm or more in the
Cryohemists                                                        control section, below the surface tier.
                                                                                                                Fibric Haplohemists
Key to Subgroups
BEDA. Cryohemists that have a layer of water within the            BEEG. Other Haplohemists that have one or more layers of
control section, below the surface tier.                           sapric materials with a total thickness of 25 cm or more below
                                         Hydric Cryohemists        the surface tier.
                                                                                                               Sapric Haplohemists
BEDB. Other Cryohemists that have a lithic contact at the
lower boundary of the control section.                             BEEH. Other Haplohemists.
                                        Lithic Cryohemists                                                    Typic Haplohemists
158                                                                                                          Keys to Soil Taxonomy



Luvihemists                                                         material 30 cm or more thick that has its upper boundary within
                                                                    the control section, below the surface tier.
Key to Subgroups                                                                                                 Terric Cryosaprists
BECA. All Luvihemists (provisionally).
                                             Typic Luvihemists      BDCD. Other Cryosaprists that have, within the organic soil
                                                                    materials, either one layer of mineral soil material 5 cm or
Sulfihemists                                                        more thick or two or more layers of mineral soil material of any
                                                                    thickness in the control section, below the surface tier.
Key to Subgroups                                                                                          Fluvaquentic Cryosaprists
BEBA. Sulfihemists that have a layer of mineral soil material
30 cm or more thick that has its upper boundary within the          BDCE. Other Cryosaprists.
control section, below the surface tier.                                                                        Typic Cryosaprists
                                            Terric Sulfihemists
                                                                    Haplosaprists
BEBB. Other Sulfihemists.                                           Key to Subgroups
                                             Typic Sulfihemists
                                                                    BDDA. Haplosaprists that have a lithic contact at the lower
Sulfohemists                                                        boundary of the control section.
                                                                                                            Lithic Haplosaprists
Key to Subgroups
BEAA. All Sulfohemists (provisionally).                             BDDB. Other Haplosaprists that have one or more limnic
                                            Typic Sulfohemists      layers with a total thickness of 5 cm or more within the control
                                                                    section.
                                                                                                              Limnic Haplosaprists
Saprists
Key to Great Groups                                                 BDDC. Other Haplosaprists that have both:

BDA. Saprists that have a sulfuric horizon within 50 cm of the         1. Throughout a layer 30 cm or thick that has its
soil surface.                                                          upper boundary within the control section, an electrical
                                         Sulfosaprists, p. 159         conductivity of 30 dS/m or more (1:1 soil:water) for 6
                                                                       months or more during normal years; and
BDB. Other Saprists that have sulfidic materials within 100            2. A layer of mineral soil material 30 cm or more thick that
cm of the soil surface.                                                has its upper boundary within the control section, below the
                                         Sulfisaprists, p. 159         surface tier.
                                                                                                        Halic Terric Haplosaprists
BDC.    Other Saprists that have a cryic soil temperature regime.
                                             Cryosaprists, p. 158   BDDD. Other Haplosaprists that have, throughout a layer
                                                                    30 cm or more thick that has its upper boundary within the
BDD.    Other Saprists.                                             control section, an electrical conductivity of 30 dS/m or more
                                          Haplosaprists, p. 158     (1:1 soil:water) for 6 months or more during normal years.
                                                                                                                 Halic Haplosaprists
Cryosaprists
                                                                    BDDE. Other Haplosaprists that have a layer of mineral soil
Key to Subgroups
                                                                    material 30 cm or more thick that has its upper boundary within
BDCA. Cryosaprists that have a lithic contact at the lower          the control section, below the surface tier.
boundary of the control section.                                                                                 Terric Haplosaprists
                                         Lithic Cryosaprists
                                                                    BDDF. Other Haplosaprists that have, within the organic
BDCB. Other Cryosaprists that have one or more limnic               soil materials, either one layer of mineral soil material 5 cm or
layers with a total thickness of 5 cm or more within the control    more thick or two or more layers of mineral soil material of any
section.                                                            thickness in the control section, below the surface tier.
                                           Limnic Cryosaprists                                           Fluvaquentic Haplosaprists

BDCC. Other Cryosaprists that have a layer of mineral soil          BDDG. Other Haplosaprists that have one or more layers of
Histosols                                                                                                                            159



fibric or hemic materials with a total thickness of 25 cm or more           layer of mineral soil material 40 cm or more thick that has
in the control section, below the surface tier.                             its upper boundary within the subsurface tier; and
                                            Hemic Haplosaprists
                                                                         2. Do not have sulfidic materials within 100 cm of the soil
                                                                         surface.
BDDH.       Other Haplosaprists.
                                                                                                                Fibric Frasiwassists
                                            Typic Haplosaprists
                                                                      BBAB. Other Frasiwassists that have more thickness of sapric
Sulfisaprists                                                         soil materials than any other kind of organic soil materials
Key to Subgroups                                                      either:

BDBA. Sulfisaprists that have a layer of mineral soil material           1. In the organic parts of the subsurface tier if there is no
30 cm or more thick that has its upper boundary within the               continuous layer of mineral soil material 40 cm or more thick
control section, below the surface tier.                                 that has its upper boundary within the subsurface tier; or
                                            Terric Sulfisaprists
                                                                         2. In the combined thickness of the organic parts of the
                                                                         surface and subsurface tiers and there is a continuous layer
BDBB.       Other Sulfisaprists.
                                                                         of mineral soil material 40 cm or more thick that has its
                                              Typic Sulfisaprists
                                                                         upper boundary within the subsurface tier.
                                                                                                                  Sapric Frasiwassists
Sulfosaprists
Key to Subgroups                                                      BBAC. Other Frasiwassists.
                                                                                                                   Typic Frasiwassists
BDAA. All Sulfosaprists (provisionally).
                                             Typic Sulfosaprists
                                                                      Haplowassists
Wassists                                                              Key to Subgroups

Key to Great Groups                                                   BBCA. Haplowassists that have a horizon or horizons, with a
                                                                                                                                            H
                                                                      combined thickness of 15 cm within 100 cm of the soil surface,        I
BBA. Wassists that have, in all horizons within 100 cm of the                                                                               S
                                                                      that contain sulfidic materials.
soil surface, an electrical conductivity of less than 0.2 dS/m in a                                           Sulfic Haplowassists
5:1, by volume, mixture (not extract) of water and soil.
                                              Frasiwassists, p. 159   BBCB. Other Haplowassists that have more thickness of
                                                                      fibric soil materials than any other kind of organic soil materials
BBB. Other Wassists that have a horizon or horizons, with a           either:
combined thickness of at least 15 cm within 50 cm of the soil
surface, that contain sulfidic materials.                                1. In the organic parts of the subsurface tier if there is no
                                           Sulfiwassists, p. 160         continuous layer of mineral soil material 40 cm or more thick
                                                                         that has its upper boundary within the subsurface tier; or
BBC. Other Wassists.                                                     2. In the combined thickness of the organic parts of the
                                           Haplowassists, p. 159         surface and subsurface tiers and there is a continuous layer
                                                                         of mineral soil material 40 cm or more thick that has its
Frasiwassists                                                            upper boundary within the subsurface tier.
Key to Subgroups                                                                                                 Fibric Haplowassists

BBAA.       Frasiwassists that:                                       BBCC. Other Haplowassists that have more thickness
   1. Have more thickness of fibric soil materials than any           of sapric soil materials than any other kind of organic soil
   other kind of organic soil materials either:                       materials either:
      a. In the organic parts of the subsurface tier if there is no      1. In the organic parts of the subsurface tier if there is no
      continuous layer of mineral soil material 40 cm or more            continuous layer of mineral soil material 40 cm or more thick
      thick that has its upper boundary within the subsurface            that has its upper boundary within the subsurface tier; or
      tier; or                                                           2. In the combined thickness of the organic parts of the
      b. In the combined thickness of the organic parts of the           surface and subsurface tiers and there is a continuous layer
      surface and subsurface tiers and there is a continuous
160	



   of mineral soil material 40 cm or more thick that has its        BBBB. Other Sulfiwassists that have more thickness of sapric
   upper boundary within the subsurface tier.                       soil materials than any other kind of organic soil materials
                                         Sapric Haplowassists       either:

BBCD.     Other Haplowassists.                                        1. In the organic parts of the subsurface tier if there is no
                                            Typic Haplowassists       continuous layer of mineral soil material 40 cm or more thick
                                                                      that has its upper boundary within the subsurface tier; or
Sulfiwassists                                                         2. In the combined thickness of the organic parts of the
Key to Subgroups                                                      surface and subsurface tiers and there is a continuous layer
                                                                      of mineral soil material 40 cm or more thick that has its
BBBA. Sulfiwassists that have more thickness of fibric soil           upper boundary within the subsurface tier.
materials than any other kind of organic soil materials either:                                                 Sapric Sulfiwassists
   1. In the organic parts of the subsurface tier if there is no
   continuous layer of mineral soil material 40 cm or more thick    BBBC. Other Sulfiwassists.
   that has its upper boundary within the subsurface tier; or                                                  Typic Sulfiwassists
   2. In the combined thickness of the organic parts of the
   surface and subsurface tiers and there is a continuous layer
   of mineral soil material 40 cm or more thick that has its
   upper boundary within the subsurface tier.
                                             Fibric Sulfiwassists
                                                                                                                                   161




CHAPTER 11

                                                                                                                  Inceptisols

Key to Suborders                                                      KF.   Other Inceptisols that have a xeric soil moisture regime.
                                                                                                                        Xerepts, p. 189
KA. Inceptisols that have one or more of the following:
  1. In a layer above a densic, lithic, or paralithic contact or      KG. Other Inceptisols.
  in a layer at a depth between 40 and 50 cm from the mineral                                                          Udepts, p. 174
  soil surface, whichever is shallower, aquic conditions for
  some time in normal years (or artificial drainage) and one or       Anthrepts
  more of the following:
      a. A histic epipedon; or                                        Key to Great Groups
      b. A sulfuric horizon within 50 cm of the mineral soil          KBA. Anthrepts that have a plaggen epipedon.
      surface; or                                                                                          Plagganthrepts, p. 161
      c. A layer directly under the epipedon, or within 50 cm
                                                                      KBB. Other Anthrepts.
      of the mineral soil surface, that has, on faces of peds or in
                                                                                                               Haplanthrepts, p. 161
      the matrix if peds are absent, 50 percent or more chroma
      of either:
                                                                      Haplanthrepts
         (1)   2 or less if there are redox concentrations; or
                                                                      Key to Subgroups
         (2)   1 or less; or
                                                                      KBBA. All Haplanthrepts (provisionally).
      d. Within 50 cm of the mineral soil surface, enough                                                   Typic Haplanthrepts           I
      active ferrous iron to give a positive reaction to                                                                                  N
                                                                                                                                          C
      alpha,alpha-dipyridyl at a time when the soil is not being
      irrigated; or
                                                                      Plagganthrepts
                                                                      Key to Subgroups
  2. An exchangeable sodium percentage (ESP) of 15 or
  more (or a sodium adsorption ratio [SAR] of 13 or more)             KBAA. All Plagganthrepts (provisionally).
  in half or more of the soil volume within 50 cm of the                                                    Typic Plagganthrepts
  mineral soil surface, a decrease in ESP (or SAR) values with
  increasing depth below 50 cm, and ground water within 100           Aquepts
  cm of the mineral soil surface for some time during the year.
                                                Aquepts, p. 161       Key to Great Groups
                                                                      KAA. Aquepts that have a sulfuric horizon within 50 cm of
KB. Other Inceptisols that have a plaggen or anthropic
                                                                      the mineral soil surface.
epipedon.
                                                                                                               Sulfaquepts, p. 167
                                            Anthrepts, p. 161
                                                                      KAB. Other Aquepts that have, within 100 cm of the mineral
KC. Other Inceptisols that have a gelic soil temperature regime.
                                                                      soil surface, one or more horizons in which plinthite or a
                                                 Gelepts, p. 173
                                                                      cemented diagnostic horizon either forms a continuous phase or
                                                                      constitutes one-half or more of the volume.
KD. Other Inceptisols that have a cryic soil temperature
                                                                                                                  Petraquepts, p. 167
regime.
                                                Cryepts, p. 167
                                                                      KAC. Other Aquepts that have either:
KE.   Other Inceptisols that have an ustic soil moisture regime.        1. A salic horizon; or
                                                  Ustepts, p. 182
162                                                                                                          Keys to Soil Taxonomy



   2. In one or more horizons with a total thickness of 25          KAFD. Other Cryaquepts that have one or both of the
   cm or more within 50 cm of the mineral soil surface, an          following:
   exchangeable sodium percentage (ESP) of 15 or more (or a
                                                                      1. Cracks within 125 cm of the mineral soil surface that are
   sodium adsorption ratio [SAR] of 13 or more) and a decrease
                                                                      5 mm or more wide through a thickness of 30 cm or more
   in ESP (or SAR) values with increasing depth below 50 cm.
                                                                      for some time in normal years and slickensides or wedge-
                                            Halaquepts, p. 166
                                                                      shaped peds in a layer 15 cm or more thick that has its upper
                                                                      boundary within 125 cm of the mineral soil surface; or
KAD. Other Aquepts that have a fragipan within 100 cm of
the mineral soil surface.                                             2. A linear extensibility of 6.0 cm or more between the
                                       Fragiaquepts, p. 165           mineral soil surface and either a depth of 100 cm or a densic,
                                                                      lithic, or paralithic contact, whichever is shallower.
KAE. Other Aquepts that have a gelic soil temperature regime.                                                      Vertic Cryaquepts
                                           Gelaquepts, p. 165
                                                                    KAFE. Other Cryaquepts that have a histic epipedon.
KAF. Other Aquepts that have a cryic soil temperature regime.                                                 Histic Cryaquepts
                                          Cryaquepts, p. 162
                                                                    KAFF. Other Cryaquepts that have, throughout one or more
KAG. Other Aquepts that have, in one or more layers at              horizons with a total thickness of 18 cm or more within 75 cm
least 25 cm thick (cumulative) within 100 cm of the mineral         of the mineral soil surface, one or more of the following:
soil surface, 25 percent or more (by volume) recognizable             1. A fine-earth fraction with both a bulk density of 1.0
bioturbation, such as filled animal burrows, wormholes, or casts.     g/cm3 or less, measured at 33 kPa water retention, and Al
                                           Vermaquepts, p. 167        plus 1/2 Fe percentages (by ammonium oxalate) totaling more
                                                                      than 1.0; or
KAH. Other Aquepts that have a histic, melanic, mollic, or
umbric epipedon.                                                      2. More than 35 percent (by volume) fragments coarser
                                        Humaquepts, p. 166            than 2.0 mm, of which more than 66 percent is cinders,
                                                                      pumice, and pumicelike fragments; or
KAI.    Other Aquepts that have episaturation.                        3. A fine-earth fraction containing 30 percent or more
                                             Epiaquepts, p. 164       particles 0.02 to 2.0 mm in diameter; and

KAJ.    Other Aquepts.                                                   a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                            Endoaquepts, p. 163          volcanic glass; and
                                                                         b. [(Al plus 1/2 Fe, percent extracted by ammonium
Cryaquepts                                                               oxalate) times 60] plus the volcanic glass (percent) is
                                                                         equal to 30 or more.
Key to Subgroups
                                                                                                             Aquandic Cryaquepts
KAFA. Cryaquepts that have, within 150 cm of the mineral
soil surface, one or more of the following:                         KAFG. Other Cryaquepts that have a slope of less than 25
                                                                    percent and one or both of the following:
   1. A sulfuric horizon; or
                                                                      1. At a depth of 125 cm below the mineral soil surface,
   2. A horizon 15 cm or more thick that has all of the
                                                                      an organic-carbon content (Holocene age) of 0.2 percent or
   characteristics of a sulfuric horizon, except that it has a pH
                                                                      more and no densic, lithic, or paralithic contact within that
   value between 3.5 and 4.0 and does not have sulfide or other
                                                                      depth; or
   sulfur-bearing minerals; or
                                                                      2. An irregular decrease in organic-carbon content
   3.   Sulfidic materials.
                                                                      (Holocene age) between a depth of 25 cm and either a depth
                                              Sulfic Cryaquepts
                                                                      of 125 cm below the mineral soil surface or a densic, lithic,
                                                                      or paralithic contact, whichever is shallower.
KAFB. Other Cryaquepts that have both a histic epipedon and
                                                                                                          Fluvaquentic Cryaquepts
a lithic contact within 50 cm of the mineral soil surface.
                                       Histic Lithic Cryaquepts
                                                                    KAFH. Other Cryaquepts that have both:
KAFC. Other Cryaquepts that have a lithic contact within 50           1. Chroma of 3 or more in 40 percent or more of the matrix
cm of the mineral soil surface.                                       of one or more horizons at a depth between 15 and 50 cm
                                          Lithic Cryaquepts           from the mineral soil surface; and
Inceptisols                                                                                                                        163



   2. A mollic or umbric epipedon.                                    2. More than 35 percent (by volume) fragments coarser
                                      Aeric Humic Cryaquepts          than 2.0 mm, of which more than 66 percent is cinders,
                                                                      pumice, and pumicelike fragments; or
KAFI. Other Cryaquepts that have chroma of 3 or more in 40
                                                                      3. A fine-earth fraction containing 30 percent or more
percent or more of the matrix of one or more horizons at a depth
                                                                      particles 0.02 to 2.0 mm in diameter; and
between 15 and 50 cm from the mineral soil surface.
                                             Aeric Cryaquepts            a. In the 0.02 to 2.0 mm fraction, 5 percent or more
                                                                         volcanic glass; and
KAFJ. Other Cryaquepts that have a mollic or umbric
                                                                         b. [(Al plus 1/2 Fe, percent extracted by ammonium
epipedon.
                                                                         oxalate) times 60] plus the volcanic glass (percent) is
                                        Humic Cryaquepts
                                                                         equal to 30 or more.
                                                                                                           Aquandic Endoaquepts
KAFK.     Other Cryaquepts.
                                              Typic Cryaquepts
                                                                    KAJE. Other Endoaquepts that have, in one or more horizons
                                                                    between the A or Ap horizon and a depth of 75 cm below the
Endoaquepts                                                         mineral soil surface, one of the following colors:
Key to Subgroups
                                                                      1. Hue of 7.5YR or redder in 50 percent or more of the
KAJA. Endoaquepts that have, within 150 cm of the mineral             matrix; and
soil surface, one or more of the following:                              a. If peds are present, either chroma of 2 or more on 50
   1. A sulfuric horizon; or                                             percent or more of ped exteriors or no redox depletions
                                                                         with chrom