Contrasting layers of soil lying one below the other, parallel or nearly parallel to the land surface. Soil horizons are differentiated on the basis of field characteristics and laboratory data. The three
major horizons are:
“A” horizon – the uppermost layer of the soil profile, often called topsoil. It is the part of the soil in which organic matter is most abundant and where leaching of soluble or unsuspended particles is the greatest.
“B” horizon – the layer immediately beneath the A horizon. This middle layer commonly contains more clay, iron or aluminum than the A or C horizons.
“C” horizon – the deepest layer of the soil profile. It consists of loose material or weathered bedrock that is relatively unaffected by biologic activity.
