Question

Explain different horizons of soil profile.

Answer 1

Following are the different horizons of soil profile:

1. Horizon O: This is the topmost layer of soil, lying just above the topsoil layer and extends from the surface to a depth of 2 inches. It is rich in organic material.
2. Horizon A: Horizon A is the topsoil. It consists of fine particles and is rich in humus. This imparts the top soil its dark colour. The topsoil is soft, porous and can retain water. Horizon A extends from about 2 inches to 10 inches below the surface.
3. Horizon B: Horizon B extends from 10 inches to 30 inches below the surface. It is called the subsoil and is rich in minerals that have seeped in the water. It also contains fine particles of soil, compactly packed together.
4. Horizon C: This layer extends from about 30 inches, down to 48 inches below the surface. It contains partly weather pieces of rocks . This layer is characterised by cracks and fissures and it is very difficult to dig below this level.
5. Horizon R: Horizon R refers to bedrock. This rock determines the composition of the soil.