Diagnostic Subsurface Horizons

-illuvial horizon formed under cultivation
-significant amounts of illuvial silt, clay and humus
-directly below Ap horizon
-thickness of 10cm or greater
-eluvial horizon that is lightly colored and low in clay and oxides (leaching)
-1cm or greater
-separate horizons that, if they were together, would meet requirements for a mollie epipedon or separate lamellae that together would be an argillic horizon
-anhydrite accumulation through neoformation and transformation
-hue of 5Y, chroma (moist and dry) of 1 or 2, and value of 7 or 8
Argillic (Bt)
-significantly higher percentage of phyllosilicate clay than overlying soil material
-clay illuviation
-total clay in illuvial horizon is greater by 1.2 times or more than the ratio in the alluvial horizon
Calcic (Bk)
-illuvial accumulation of calcium carbonates
-15% more CaCO3 equivalent, and 5% identifiable secondary carbonates
-“Petrocalcic” if secondary CaCO3 accumulated and cemented
Cambic (Bw)
-has not undergone enough illuviation to become argillic
-sandy loam or finer (not loamy sand)
-different color and structure from C horizon due to chemical transformations, or removals or a combination
-colors that do not change on exposure to air
-absence of rock structure
Duripan (Bq)
-silica-cemented subsurface horizon
-can occur in conjunction with petrocalcic horizon
-accumulation of silica (coatings, lenses, bridges, etc)
-pan is cemented or indurated in more than 50% of the volume of some horizon
Fragripan (Bx)
-evidence of pedogenesis
-coarse prismatic, columnar or blocky structure
-not effervescent
-layer is 60% or more of the volume, a firm or firmer rupture-resistence class, a brittle manner of failure at or near field capacity and virtually no roots
-degredation of an argillic, kandic or natric horizon from which clay and free iron oxides are removed
-eluvial part that constitutes 15-85% (by vol) of glossic horizon
Gypsic (By)
-accumulated or transformed gypsum
-not cemented by gypsum (with or without cementing agent)
-5% or more of gypsum
-“Petrogypsic” if secondary gypsum has accumulated or been transformed and cemented (40% or more gypsum)
-accumulation of Fe and Al oxides and kaolinite clays
-low cation holding capacity
-product of intense weathering
-loamy VF sand or finer
Natric (Btn)
-like argillic with the addition of sodium
->15% exchangeable sodium
-columnar structure
-evidence of clay illuviation
Oxic (Bo)
-highly weathered subsurface very high in Al and Fe
-humid and subtropical environments
-10% weatherable minerals in sand, silt or clay, all other minerals have weathered to elements
-does not have antic soil properties
-30 cm or greater
-sandy loam or finer
cemented by iron (or iron and manganese) and organic matter
Salic (Bz)
accumulation of salts more soluble than gypsum
-dark subsurface horizon that formed under free drainage
-illuvial humus that is neither associated with Al nor dispersed by Na
-does not have high CEC in its clay
-lower color value and/or chroma than overlying horizon
Spodic (Bhs or Bs)
-illuvial layer with 85% or more spodic materials (greater than 2.5 cm)
-spodic materials are colloidal organic matter, aluminum oxide and iron
-underlies O, A or E horizon
-common in leached forests of cool humid climates
-on sandy PM

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Diagnostic Subsurface Horizons. (2018, Jan 01). Retrieved from https://paperap.com/paper-on-diagnostic-subsurface-horizons/

Diagnostic Subsurface Horizons
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