Lecture 3a Naming Soil Horizons

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Lecture 3aNaming Soil Horizons

• Soil horizons (layers in the soil) are named so
  differences between soils can be identified.
• Naming soil horizons takes practice

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• When soil scientists are describing a soil they
  will discuss a lot about what they are seeing and
  how it should be named.
• And what they are not seeing and what it should
  not be called ?

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Soil Judging

• Students wanting more practice at naming soil
  horizons should take Soil 4511 and try out for
  the Soil Judging Team Students that participate
  in the Soil Judging contest get more practice
  with different soils from the region. (MN, SD,
  ND,MO,IA,KS,NE.
• The contest this fall is in Minnesota near
  Cloquet.

Contest in Kansas 2006
2007 UM Soils Team in the Team Pit No. 1 in
southwest Iowa Left to right Meryl Larson, Erin
Andrews, Nick Reep, and Nick Saumweber
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Organic Horizons

• O - horizon - organic material (no mineral
  materials)
  1) forest litter
  2) organic soil or peat
  soils, or muck
• Oi - undecomposed (fibris)
• Oe - moderate decomp. (hemis)
• Oa - decomposed (sapric)

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Organic Soil Profile
This trenching machine is digging through the Oe
horizon of an organic soil. Trenches needed
to remove water so the peat will dry
before harvest.
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Organic Soil Horizons in a forest litter
Oi
Oe
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Processes of Mineral Soil Horizon Formation

• A. Additions - H2O, organic matter,air, soil
  particles, salt
• B. Losses - H2O, organic matter, CO2 ,
  nutrients by plant removal
• C. Transformations - Changes to soil
  structure, development of clay minerals,
  weathering of minerals to elements, chemical Rx
• D. Translocations - movement from one horizon to
  another of O.M. Clay, Water, Iron,
  Nutrients in colloidal size, (very small
  particles) clay films on peds are evidence of
  this translocation clay (film) coating

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Mineral Soil Horizons

• A horizon - surface
  horizons that
  accumulate
  O.M.
• Ap plowed soil

Ap
EB
Bt
Ap
BC
C
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E Horizons

• E - (formerly A2) - Translocation out - Zone of
  Eluviations - Leaching out
• lighter in color than horizons above or below

A E E/B Bt BC C
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B Horizons- two kinds

• a) Translocation in -
  below an A, E, or O with
  an accumulation of clay, iron,
  humus (O.M. decomposed.)
  or carbonates (CaCO3)
  zones of illuviation
  
• b) or alteration of the
  original parent material,
  development of color or
  structure - Bw

Bt
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C Horizons

• C - little affected by pedogenic processes and
  lack properties of O-A-B-E- or is the Parent
  Material

Solum
A B
C horizon
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Rock Horizons

• R hard rock
• Cr Soft Rock

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Subscripts - all B horizons have a subscript,
most transition horizons do not.

• a - sapric - organic soils - well decomposed
• b - buried soil horizon
• d - dense - geogenic soil material
  (compacted by glacier)
• e - hemic - mod. decomp. - organic soil
• f - frozen soil - permanently frozen,
  permafrost
• g - gleyed soil - gray color due to low O2 -
  reduction of Fe
• h - accumulation of humus - O.M. other than
  in the A or O horizons
• i - fibric - organic - non-decomposed
• k - accumulation of calcium carbonate (CaCO3)
• m - cementation - hard - indurated

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Subscripts cont.

• n - sodium accumulation
• p - plowing - only used with A
• q - silica accumulation - very weathered or
  old soil
• r - soft rock - used with C or Cr
• s - sesquioxides (1.502) (Fe2O3) accumulation
  of Fe and Al - red color
• ss slickensides present shiny surface on ped
  face caused from soil rubbing against soil
• t - clay accumulation - clay films
• w - color or structure development (Bw)
• x - Fragipan - hard, dense layer that
  developed with time
• y - gypsum accumulation (CaSO4)
• z - salts more soluble than gypsum
  (KCL - NaCl -
  NaSO4)

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Transition Horizons

• AB - Like A - some of B
• BA - Like B - some of A
• AE AC BC
  
  
• E/B - Both E and B particles
  are present -
• B E used for soils
  with
  Lamellae
  - thin
  bands of accumulating
  clay and
  iron in sandy soils

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Lithologic Discontinuity

• A1
• A2
• 2B
• Designated by number in front of horizon.
• (More than one
  parent material)

2 parent materials
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Practice at naming horizons Soil from Badlands
of North Dakota---Texture of horizons 1,2,3,4
loam---Note Carbonates in horizon 3
DYAD Name 4 horizons Using one transition
horizon

• ---
• A
• ---
• AB
• ---
• Bk
• ---
• C

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Sandy soil from Northeast MinnesotaTexture of
Horizon 1,2,3,4 Sand
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Goodhue County Soil, Southwest of Redwing
Mn.Texture of horizon 1 2 Silt Loam, Hrz 5
Silty ClayHrz. 4 Cobbly loam, Hrz. 5 Loam

• A
• E
• Bt
• 2BC
• 2C

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This is not soil. It is a "rock outcrop"
The End
This is not soil. It is "dune land"