Lecture 3a Naming Soil Horizons
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Transcript of 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 trenchingmachine is diggingthrough the Oe horizon of an organic soil.
Trenches needed to remove water so thepeat will dry beforeharvest.
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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
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
AE
E/B
Bt
BCC
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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
C horizon
Solum = A + B
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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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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)
Subscripts cont.
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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
---
A --- AB --- Bk --- C
DYAD – Name 4 horizons Using one transition horizon
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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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