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Introductory Soils2 - AAMU Myspace Login


									Soil profile showing major horizons
              The Soil Profile
• Soil profile is a vertical section of soil from the
  earth’s surface extending to the parent material
  that shows the individual horizons of the soil.

• Soil horizon is a layer of soil approximately
  parallel to the soil surface with distinct
  characteristics produced by soil forming
Identification and Nomenclature
         of Soil Horizons
• In making soil examinations, every horizon or
  layer is described separately.

• Three kinds of symbols are used in various
  combinations to designate horizons and layers.
  They are:
   – Capital letters
   – Lower case letters
   – Arabic numerals
• Capital letters are used to designate the
  master horizons and layers.
• Lower case letters are used as suffixes to
  indicate specific characteristics of the
  master horizon and layer.
• Arabic numerals are used both as suffixes to
  indicate vertical subdivisions within a
  horizon or layer and prefixes to indicate
  lithological discontinuities.
  1. Master Horizons and Layers

• The capital letters O, A, E, B, C, and R
  represent the master horizons and layers of

• The capital letters are the base symbols to
  which other characters are added to
  complete the designations.
        O Horizons or Layers
           (Organic Soil Horizon)

• Layers dominated by organic material
• Some are saturated with water for long
  periods of time or were once saturated but
  are now artificially drained.
                   A Horizons
• Mineral horizons that formed at the surface or
  below an O horizon and
   – 1) are characterized by an accumulation of humified
     organic matter intimately mixed with the mineral
   – 2) have properties resulting from cultivation,
     pasturing, or similar kinds of disturbance.
   – 3) Usually coarser in texture having lost some of its
     finer materials by translocation or erosion
               E Horizons
• Mineral horizon in which the main feature
  is loss of silicate clay, iron, aluminum, or
  some combination of these, leaving a
  concentration of sand and silt particles of
  quartz or other resistant minerals.
• E horizons are usually, but not necessarily,
  lighter in color than an underlying B
                 B Horizons
• Horizons that formed below an A, E, or O
  horizon and are dominated by obliteration
  of all or much of the original rock structure
  and by the following:
  – illuvial concentration of silicate clay, iron,
    aluminum, humus, carbonates, gypsum, or
    silica, alone or in combination;
  – evidence of removal of carbonates
  – residual concentration of sesquioxides;
• coatings of sesquioxides that make the horizon
  lower in color value, higher in chroma, or
  redder in the hue than overlying and
  underlying horizons;
• alteration that forms silicate clay or liberates
  oxides or both and that forms granular, blocky,
  or prismatic structure;
• Any combination of these.
       C Horizons or Layers
• Horizons or layers excluding hard bedrock,
  that are little affected by pedogenic
  processes and properties of O, A, E, or B
• The material of C horizons may be either
  like or unlike that from which the solum
  presumably formed.
                 R Layers
• Hard bedrock
• E.g. granite, sandstone, basalt, quartzite,
  and indurated limestone.
     2. Transitional Horizons
• Horizons dominated by properties of one master
  horizon but having subordinate properties of
• Two capital letter symbols are used as EB, BE,
• Master horizon that is given first designates the
  kind of horizon whose properties dominate the
  transitional horizon
• E.g. EB has characteristics of both an overlying E
  and an underlying B horizons, but is more like E
  than B.
• Major pedogenic subdivisions within O, A,
  and B horizons of mineral soils are
  indicated by a primary Arabic number e.g.
  O1, O2, B1, B2 etc.
• Designations of common subdivisions of
  soil horizons are as follows;
• Oi, Oe, Oa, A, E, AB, E/B, AC, BA, BE,
  B/E, BC, CB, B, Bw.
    3. Subordinate distinctions within
        master horizons and layers

Lower case letters are used as suffixes to designate
  specific kinds of master horizons and layers. E.g.
  a B horizon which is permanently frozen is
  designated Bf. The lower case letter f indicates
  frozen horizon. The symbols and their meanings
  are as follows:
a - sapric - organic soils - well       n - sodium accumulation
    decomposed                          p - plowing - only used with A
b - buried soil horizon
                                        q - silica accumulation - very
d - dense - geogenic soil material          weathered or old soil
e - hemic - mod. decomp. - organic
    soil                                r - soft rock - used with C or Cr
f - frozen soil - permanently frozen,   s - sesquioxides - accumulation of
    permafrost                              Fe and Al - red color
g - gleyed soil - gray color due to     t - clay accumulation - clay films
    low O2 - reduction of Fe            w - color or structure development
h - accumulation of humus other         x - Fragipan - hard, dense layer
    than in the A or O horizons             that developed with time
i - fibric - organic - non-
    decomposed                          y - gypsum accumulation (CaSO4)
k - accumulation of calcium             z - salts more soluble than gypsum
    carbonate (CaCO3)                       (KCL - NaCl - NaSO4)
m - cementation - hard - indurated

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