Lecture 3a

Naming Soil Horizons   Soil horizons (layers in the soil) are named so differences between soils can be identified.

Naming soil horizons takes practice

  When soil 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

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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)

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.

Oi

Organic Soil Horizons in a forest litter

Oe

    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

Mineral Soil Horizons   A horizon - surface horizons that accumulate O.M. EB Ap = plowed soil Bt BC C

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

B Horizons- two kinds

:

  below an A, E, or O with iron, humus (O.M. Bt decomposed.) zones of

illuviation

b) or alteration of the structure - Bw

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

Rock Horizons

 

R = hard rock Cr = Soft Rock

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

           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)

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

Lithologic Discontinuity

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

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

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Bk ---

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-- C

Sandy soil from Northeast Minnesota Texture of Horizon 1,2,3,4 = Sand

Goodhue County Soil, Southwest of Redwing Mn.

Texture of horizon 1 & 2 = Silt Loam, Hrz 5 = Silty Clay Hrz. 4 = Cobbly loam, Hrz. 5 = Loam  A  E    Bt 2BC 2C