Soil Profile

Soil Profile Because the particles that make up soil are deposited at different times and from different places, the soil forms in layers, which we call HORIZONS

O Horizon - Organic material that gathers on top of the soil layers

Composed of HUMUS (decayed organic matter) O Horizon A Horizon Also called TOPSOIL Composed of HUMUS (decayed organic matter) Fine texture Ideally should be at least 18 cm deep

B Horizon Also called SUBSOIL O Horizon A Horizon B Horizon Also called SUBSOIL Made up of an accumulation of finely weathered material that have washed down from the A Horizon Nutrients that accumulate here can be “called back” to the A Horizon when needed (drought, etc.), so the B horizon acts as a storehouse of nutrients for the A horizon.

Coarse, less weathered material O Horizon A Horizon B Horizon C Horizon Also called REGOLITH Coarse, less weathered material Under very dry conditions this horizon may provide minerals to the soil layers above This horizon is too deep to be reached by most root systems , so it really has no effect on soil fertility

The solid foundation on which all the other layers sit O Horizon A Horizon B Horizon C Horizon D Horizon Also called BEDROCK The solid foundation on which all the other layers sit Has nothing to do with soil fertility

SALINIZATION (CALCIFICATION) Leaching - The process by which mineral salts in the upper horizons are moved downward SALINIZATION (CALCIFICATION) - The accumulation of soil salts in the topsoil as heat evaporates the moisture out of the soil O Horizon A Horizon B Horizon C Horizon D Horizon CAPILLARY ACTION Occurs in dry areas As surface water evaporates it is replaced by water from further down in the soil profile. In this manner water and nutrients can move upward.