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NTCHS Field Indicators of Hydric Soils

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					 Field Indicators of Hydric Soils


   Natural Resources Conservation Service
            in cooperation with the
National Technical Committee for Hydric Soils
                Hydric Soil Identification
   Field Indicators
     – the preferred method based on observable soil morphology (soil color, organic
        layers, etc.)
   Hydric Soil Criteria
     – database search of estimated soil properties
           designed to generate a list of soils that are likely to be hydric

   Monitoring Data
     – used with technical standard for sites with no observable hydric morphology
                 Introduction

   Field indicators are soil morphological
    features used to identify hydric soils
   The features result from soil genesis in the
    presence of “anaerobic conditions”
   They are used for on-site verification of
    hydric soils
              Why Indicators?
   Updates due to improved understanding and
    recent research
   There are soils on the hydric list that may or
    may not be hydric
   NAS 1995, “field indicators should be used
    for on-site verification”
        NTCHS Field Indicators

   Refinements of the 1987 Corps indicators


   Address problem soils
    Development of the Indicators

   Continuous process
    – ongoing since the mid-1980’s
   Interagency
    – including universities, private
      sector, federal, state, and local
      agencies
   Multi-disciplinary
    – soil scientists, hydrologists,
      botanists
        Hydromorphic Processes
              Identified
   Reduction, translocation, and precipitation
    of iron and manganese
   Accumulation and differential translocation
    of organic matter
   Reduction of sulfur
                    Regional

   Lists of indicators by Land Resource
    Region (LRR)
   Addresses “problem” soils
    – Mollisols and Vertisols
    – Sandy soils
    – Flooded and ponded soils
    – Red parent materials
        Specific Sections or Zones
   Layers with :
    – high value and low chroma, or
    – redoximorphic features, or
    – organic material accumulations
   at a specified depth
   of certain thickness
      Diagnostic Redoximorphic
            Morphology
   Redox concentrations (Fe or Mn) that are
    distinct or prominent
   Redox depletions (Fe or clay) with high value
    and low chroma


   Depleted Matrix
   Reduced Matrix
   Gleyed Matrix
        Hydric Soil Identification
   Field Indicators
    – the preferred method based on observable soil
      morphology (soil color, organic layers, etc.)
   Hydric Soil Criteria
    – database search of estimated soil properties
           designed to generate a list of soils that are likely to be hydric
   Monitoring Data
    – used with technical standard for sites with no
      observable hydric morphology
          Depleted Matrix
     (majority or most extensive)
   5/1 or higher*
   6/2 or higher*
   4/1, 4/2, or 5/2 plus
    > 2% D or P redox conc.

*All A and E horizons
  must also have > 2%
  D or P redox conc. even
  with chroma of 1
         Depleted Matrix (on any hue (page))

No redox conc. needed
Unless this is an A or E horizon,
then need > 2% D or P



> 2% D or P Redox conc.
Needed, Regardless of horizon
          Redox Distinctness Test
Comparing the redox concentration color to any other color


If both colors have              difference must be
 the same hue,                   > 3 value or > 2 chroma

If colors are 1 hue apart,       difference must be
                                 > 1 value or > 1 chroma, or
                                 any of the values or chromas
                                 is > 3 if the value and chroma
                                 are the same on both hue

Colors are 2 hues or more apart (Gley page has multiple hues)
                      Reduced Matrix

Soils have high value,            before
low chroma in situ
but color changes
when exposed to air                        after
   reduced Fe is present
   Fe+2 is oxidized to Fe+3
    upon exposure to O2
    (does not require microbes)
            Gleyed Matrix
    Hue           V     C
   5G           >4   1 or 2

   Other Gley   >4     1

   N            >4

   5Y (test)     4     1
Depleted Matrix --- Gleyed Matrix




4/2, 5/2, 4/1    5/1+, 6/2+       Value > 4 on
with 2% redox    with or          gley pages
concentrations   without redox
                 concentrations
Gleyed Matrix
        Three Major Divisions

   All Soils
    – Use regardless of soil texture
    – Mostly surface layers of organic material
   Sandy Soils
   Loamy Soils
    – Use sandy indicators in sandy layers,
      loamy indicators in loamy layers
Organic vs. mineral material
Organic Material Indicators

                Muck of any thickness,
                Or thick mucky peat or peat
                 OC = clay/10 + 12 or > 18

                Mucky modified mineral
                texture of specific thickness
                 OC = clay/10 + 5 or > 12
          ?
                Round to nearest whole #
          “All Soils” Indicators

   A1, Histosols
   A2, Histic Epipedon
   A3, Black Histic
   A4, Hydrogen Sulfide
   A1. Histosols

16 of the top 32 inches
40 of the top 80 cm
Consist of Organic
soil materials
 A2, Histic Epipedon
 A3, Black Histic
A Histic Epipedon has
8 of the top 16 inches or
20 of the top 40 cm
Organic soil materials

Black Histic does not
have to be as thick, but
must have hue 10YR or
yellower, value 3 or less,
and chroma 1 or less
A4, Hydrogen Sulfide


This is a
Sulfihemist.
Requires odor of
hydrogen sulfide
(rotten eggs) within
30cm of surface.
                     All Soils

A5, Stratified Layers
   Several stratified layers
    starting within the upper
    15 cm of the soil surface.
    One or more of the layers
    has value 3 or less with
    chroma 1 or less and/or it
    is muck, mucky peat, peat,
    or mucky modified
    mineral texture.
A5 in Loamy materials (left) & Sandy materials (right)
                    All Soils

A6, Organic Bodies
   Presence of 2% or
    more organic bodies
    of muck or a mucky
    modified mineral
    texture, approximately
    1 to 3 cm in diameter,
    starting within 15 cm
    of the soil surface.
                     All Soils

A7, 5 cm Mucky Mineral
  A layer of mucky
    modified mineral             Mucky silt loam
    texture 5 cm or more
    thick starting within
    15 cm of the soil
    surface.
                      All Soils

A8, A9, A10
A layer of muck x cm or           muck
   more thick with value 3 or
   less and chroma 1 or less
   starting within 15 cm of
   the soil surface.
   A8 = < 1 cm thick
   A9 = 1 cm thick
   A10 = 2 cm thick
                        Sandy Soils

   A layer less than 25 cm depth is loamy fine sand
    or coarser
   “Control Section” < 15 cm depth
   Indicators include:
    – organic surface layers
    – differential translocation of OM
           streaking of OM
           Fe stripped matrix
70% coated grains in Sandy Soils




70 % - unusual amount
                        50 % - normal amount
                      Sandy Soils

S1, Sandy Mucky Mineral
  A mucky modified mineral      Mucky fine sand
    layer > 5 cm (2 in) thick
    starting within 15 cm of
    the soil surface.
                     Sandy Soils

S3, 5 cm Mucky Peat or Peat
 A layer of mucky peat or peat 5 cm or more thick with
   color value < 3 and chroma < 2 starting within 15 cm of
   the soil surface.




                                        Mucky peat
                      Sandy Soils

S4, Sandy gleyed matrix
A gleyed layer that occupies > 60%
  of the volume starting within 15
  cm of the soil surface.




           Gleyed matrix
  A10, 2 cm Muck




  S5, Sandy Redox
A layer > 10 cm (4 in) thick
starting within 15 cm of the
surface, with > 60% matrix
chroma < 2 and > 2%
P or D redox conc.
               S6, Stripped Matrix
Variegated pattern of redox conc. and areas stripped of OM
and/or Fe. Stripped areas occupy > 10% of the volume of a
layer starting with 15 cm of the surface.




            Organic matter            Fe and organic matter
                    Sandy Soils

S7, Dark surface
 A layer > 10 cm (4 in) thick
    starting within 15 cm of
    the soil surface with
    matrix value < 3 and
    chroma < 1. > 70% of the
    grains are coated with
    OM. The layer below has
    chroma < 2.
                      Sandy Soils

S8, Polyvalue below surface
A layer > 10 cm (4 in) thick
   starting within 15 cm of the
   soil surface with matrix
   value < 3 and chroma < 1. >
   70% of the grains are coated
   with OM. The layer below
   has a variegated color pattern
   with > 5% volume value < 3
   and chroma < 1 and the
   remainder with value > 4 and
   chroma < 1 .
                     Sandy Soils

S9, Thin dark surface
 A layer > 10 cm (4 in) thick
    starting within 15 cm of
    the soil surface with matrix
    value < 3 and chroma < 1.
    > 70% of the grains are
    coated with OM. The layer
    below has value < 4 and
    chroma < 1 down to 30 cm
    depth or to top of a spodic
    horizon that starts within
    30 cm.
                Loamy Soils

   If any layer in the upper 25 cm is loamy
    very fine sand or finer
   Control Section usually starts within 25-30
    cm
   Most indicators are based upon the
    reduction/oxidation of Fe
F1, Loamy Mucky
Mineral

A mucky modified
mineral layer > 5 cm
(2 in) thick starting
within 15 cm of the
soil surface.
 F2, Loamy gleyed
 matrix




A gleyed layer that occupies
  > 60% of the volume
  starting within 15 cm of
  the soil surface.
F3, Depleted Matrix


A layer > 15 cm (6 in)
thick with chroma < 2
in > 60% of the volume
starting within 25 cm
of the soil surface.
           Or
Minimum thickness is
5 cm if it starts within
the surface 15 cm.
 F4, Depleted Below
 Dark Surface

A layer > 15 cm (4 in) thick
starting within 30 cm of the
soil surface with depleted
matrix that has > 60%
chroma < 2. The layer(s)
above have value < 3 and
chroma < 2.
 F5, Thick Dark
 Surface

A layer > 15 cm (4 in) thick starting
below 30 cm of the soil surface
with depleted or gleyed matrix that
has > 60% chroma < 2. The layer(s)
above have hue N and value < 3 to
a depth of 30 cm and value < 3 and
chroma < 1 in all other parts of the
epipedon.
                     F6, Redox Dark Surface


A layer > 10 cm (4 in) thick entirely
    within the upper 30 cm with
a. matrix value < 3 and chroma < 1
    and > 2% D or P redox conc., or
b. matrix value < 3 and chroma < 2
    and > 5% D or P redox conc.

Redox conc. are not nodules or
   concretions
                  F7, Depleted Dark Surface


Redox depletions in a layer > 10 cm
   (4 in) thick entirely within the
   upper 30 cm with
a. matrix value < 3 and chroma < 1
   and > 10% redox depletions with
   value > 5 and chroma < 2, or
b. matrix value < 3 and chroma < 2
   and > 20% redox depletions with
   value > 5 and chroma < 2.
            Loamy Depressions
F8, Redox Depressions
• In closed depressions subject to
ponding, 5% or more redox
concentrations in a layer 5 cm
thick entirely within the upper 15
cm of the soil surface.

F9, Vernal Pools
• Indepressions, presence of a
depleted matrix 5 cm thick
entirely within the upper 15 cm.
               Loamy Soils

Depressional
landform in
the High
Plains
Depressional
Landform
(Vernal Pool)
                   Loamy Soils
F12, Iron/Manganese Masses
   On floodplains, a layer 10
    cm or more thick with
    40% or more chroma 2 or
    less, and 2% or more
    redox concentrations as
    soft Fe/Mn masses with
    diffuse boundaries. The
    layer occurs entirely
    within 30 cm of the soil
    surface.
                   Loamy Soils

F13, Umbric Surface,
 LRR’s P and T.
   In depressions and other
    concave landforms, a layer
    15 cm or more thick starting
    within the upper 15 cm of
    the surface with value 3 or
    less and chroma 1 or less,
    underlain by a layer 10 cm
    or more thick with chroma
    2 or less
 Test Indicators
TF2, Red Parent Material
In parent material with a
hue of 7.5YR or redder, a
layer at least 10 cm thick
with a matrix chroma of 4
or less and 2% or more
redox depletions and/or
redox concentrations as soft
masses and/or pore linings.
The layer is entirely within
30 cm of the soil surface.     parent material
                               with a hue of
                               7.5YR or redder
Test Indicators – TF2
TF4
TF7
TF10
                   Glossary
   These terms are either defined for the first
    time or they have definitions that are
    slightly different from the definitions in the
    referenced materials.
   Gleyed Matrix              70% coated grains
   Depleted Matrix
   Mucky Modified
   Distinct “redox conc.”
                    Summary
Field Indicators of Hydric Soils:
     are based upon soil genetic processes
     use hydromorphic features
     are “test positive”
     represent “state of the science”
     are regionalized
     will require further development, testing, and
      validation
     can be used in Clean Water Act wetland
      delineations
      – 17 Sept 1998 John Studt memo

				
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