Which statement about soil layers is true?

• A. Topsoil is the uppermost layer
• B. Subsoil is the uppermost layer
• C. Parent material is the uppermost layer
• D. Leaching is a soil layer

Answer: (A)

Think about how soils are built in layers. The topmost part of the soil you see supporting plants is topsoil, the layer where most roots grow and where the soil is richest in organic matter and nutrients. That makes it the uppermost layer of the soil profile in everyday terms, which is why this statement is true.

Beneath topsoil is subsoil, which has more minerals but less organic matter. Deeper still is parent material, the partly weathered rock or other material that forms the basis of the soil. Leaching isn’t a layer at all—it's the process of water moving dissolved nutrients downward through the soil.