Which soil layer is most fertile and supports most root growth?

• A. Topsoil
• B. Sand
• C. Bedrock
• D. Subsoil

Answer: (A)

The surface layer, topsoil, is the most fertile and best for root growth. It sits where most organic matter—the decayed plant and animal material—accumulates, providing a rich supply of nutrients that roots can absorb. This layer also has a crumbly, well-structured texture with plenty of air spaces, which helps roots access oxygen and move water and nutrients efficiently. Microbial life in topsoil further helps break down organic matter into usable nutrients, boosting fertility.

In contrast, sand drains quickly and doesn’t hold nutrients well; bedrock is solid and inaccessible to most roots; subsoil sits beneath topsoil and is usually denser with less organic matter, offering fewer nutrients and poorer root-friendly conditions.