Characteristics that differentiate soil horizons Color Texture Density Structure Consistence Organic Matter content Acidity Mineral Accumulations Biological activity

Original Russian Concept

o Zone of eluviation Zone of illuviation

Only 1 letter “l” E

Prairie dominated the flat expanses Forest dominated the hilly land thin A horizon weak E horizon strong B horizon Illinois once was covered by a complex mix of prairie and forest Prairie dominated the flat expanses Forest dominated the hilly land

Young Soil in NC Old Soil in NC Poorly Defined Horizons Low Degree of Weathering Slightly Leached Thin Solum Well Defined Horizons High Degree of Weathering Highly Leached Thick Solum http://www.mo15.nrcs.usda.gov/features/gallery/

Water driven translocations Illuviation Eluviation Illuviation Illuviation http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/soil_systems/soil_development_profiles.html

Adapted from Stewart (1990) Precipitation plus solutes, aerosols and particulates Additions Additions Sediment Loss of gases N2, N2O, CO2 Losses Soil forming processes Sediment Losses Capillary rise of dissolved ions E(i)lluviation of clay CaCO3 dissolved ions dissolved OM Organic residues  humus Primary  Secondary minerals minerals TRANSLOCATIONS TRANSFORMATIONS TRANSLOCATIONS Capillary rise of salts Additions Leaching of dissolved ions & OM Losses Adapted from Stewart (1990)

Conceptual chronosequence http://courses.soil.ncsu.edu/resources/soil_classification_genesis/soil_formation/soil_transform.swf

Master horizons are designated using capital letters Horizon nomenclature Master horizons are designated using capital letters (O, A, E, B, C). Lowercase suffixes (aka subscripts) are used to denote specific horizon characteristics or features (e.g., Oi, Oe, Oa, Bt, Btg, Bx) Numbers following master horizon letters indicate unspecified changes in properties (e.g., A2, A3) Numbers preceding master horizon letters indicate changes in parent material (e.g., 2A, 2B) Combinations of master horizon letters indicate transition zones (e.g., AE, BC)

Sometimes a soil’s horizons are very difficult to interpret. Consider the profile to the left: How many different parent materials are represented ? Where would one find such a soil ?

The best way to look at soil profiles

Soil profiles can be investigated using a soil auger

What is this guy doing ??

Making a soil monolith

Hue Munsell color book Value Chroma Low #s

“Texture by feel”

Soil Structure Platy Blocky Granular crumb structure Columnar Prismatic

Soil Consistence Loose Friable Firm Very Firm