Course: SLF 150 Pasture Management

Reading & Audio Visual

Soil Structures
Soil Structures

Soil has different layers called horizons. The picture at the right shows a general example of the layers, their appearance and their depth in inches.

The O horizon is the top layer at the soil surface. It consists of surface litter, such as fallen leaves, sticks and other plant material, animal waste, and dead organisms. A distinct O horizon may not exist in all soil environments (e.g., desert soil).

Below the O horizon is the A horizon This layer contains organic humus, which usually gives it a distinctive dark color.

The B horizon or sub-soil is the next layer down from the surface. It consists mostly of inorganic rock materials, such as sand, silt, and clay.

The C horizon sits atop bedrock and, therefore, is made up of weathered rock fragments. The bedrock is the source of the parent inorganic materials found in the soil.