Soil Horizons

Soil Horizon

The various layers exposed in a pedon; roughly parallel to the surface and identified as O,A,E,B, and C, residing about bedrock designated R

Soil Profiles

Letters assigned to each soil horizon for identification

O Horizon (Humus)

Top of a profile, derived from plant and animal litter that was deposited on the surface transformed into humus

Humus

Mixture of decomposed organic materials and is usually dark in color

R Horizon (Bedrock)

Bottom of the soil profile consisting of either unconsolidated (loose) material or consolidated bedrock

A Horizon (Top Soil)

Darker and richer in organic content than lower horizons, presence of humus and clay particles, provide essential chemical links between soil nutrients and plants

E Horizon (Eluviation)

Made up of coarse sand, silt and resistant minerals, clays and oxides of aluminum and iron are leached (removed by water) and are carried to lower horizons by water, sometimes this horizon is not there

Eluviation

Process in which water rinses upper horizons and removes fine particles and minerals

B Horizon (illuviation, subsoil)

May exhibit reddish or yellowish hues, accumulate clays, aluminum and iron, dominated by illuviation

Illuviation

A depositional process

C Horizon (Regolith)

Weathered bedrock or weathered parent material, excluding the bedrock itself , not affected much by soil operations, lies outside of biological influences, plant roots rare