Which soil horizon is commonly referred to as subsoil?

Which soil horizon is commonly referred to as subsoil?

• A. Horizon A
• B. Horizon D
• C. Horizon B
• D. Horizon C

Answer: (C)

The subsoil is the layer that sits beneath the surface soil and is where materials washed out of the upper layer accumulate. This is the B horizon, formed by illuviation—the downward movement and deposition of clay, iron oxides, and other minerals from above. It usually has less organic matter and life than the topsoil, and it’s often more compact, playing a key role in storing water and minerals for plant roots. So, the layer commonly called subsoil is the underground horizon that lies below the topsoil and above the parent material. The topsoil (uppermost, rich in organic matter) is not subsoil, and the parent material layer beneath (and any bedrock-related horizons) are not the subsoil. Some soils may include a D horizon in certain classifications, but that is not the standard subsoil.

The subsoil is the layer that sits beneath the surface soil and is where materials washed out of the upper layer accumulate. This is the B horizon, formed by illuviation—the downward movement and deposition of clay, iron oxides, and other minerals from above. It usually has less organic matter and life than the topsoil, and it’s often more compact, playing a key role in storing water and minerals for plant roots.

So, the layer commonly called subsoil is the underground horizon that lies below the topsoil and above the parent material. The topsoil (uppermost, rich in organic matter) is not subsoil, and the parent material layer beneath (and any bedrock-related horizons) are not the subsoil. Some soils may include a D horizon in certain classifications, but that is not the standard subsoil.