Which horizon is commonly described as the subsoil in a soil profile?

Which horizon is commonly described as the subsoil in a soil profile?

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

Answer: (A)

In a soil profile, the layer beneath the surface that holds minerals moved down from above is the subsoil, known as Horizon B. This horizon forms from illuviation, where clay, iron, and other materials accumulate as they are washed out of the upper horizons. It’s typically less organic-rich and more compact than the topsoil (Horizon A), and its color can shift to reddish-brown or yellow-brown due to iron oxides. Because it’s denser and often has finer texture, the B horizon can be a barrier to deep root growth, affecting drainage and how water is stored in the soil. For gardeners, recognizing the B horizon helps explain why roots may spread more within the surface layer and why deep cultivation or soil amendments might be needed to improve root penetration and moisture availability. Horizon A is the topsoil rich in organic matter; C is the weathered parent material; D is not a standard horizon in most profiles.

In a soil profile, the layer beneath the surface that holds minerals moved down from above is the subsoil, known as Horizon B. This horizon forms from illuviation, where clay, iron, and other materials accumulate as they are washed out of the upper horizons. It’s typically less organic-rich and more compact than the topsoil (Horizon A), and its color can shift to reddish-brown or yellow-brown due to iron oxides. Because it’s denser and often has finer texture, the B horizon can be a barrier to deep root growth, affecting drainage and how water is stored in the soil. For gardeners, recognizing the B horizon helps explain why roots may spread more within the surface layer and why deep cultivation or soil amendments might be needed to improve root penetration and moisture availability. Horizon A is the topsoil rich in organic matter; C is the weathered parent material; D is not a standard horizon in most profiles.