Which soil horizon is primarily composed of topsoil?

The A horizon, commonly referred to as the topsoil, is the uppermost layer of soil in the soil profile. It is characterized by its rich content of organic matter, which is essential for plant growth, making it vital for agriculture and ecosystems. This horizon is where most of the biological activity occurs, including the presence of roots, microorganisms, and nutrient cycling.

The A horizon is typically darker in color due to the accumulation of organic material, which not only aids in soil fertility but also improves soil structure and moisture retention. Given that topsoil is crucial for supporting plant life, understanding its composition and functions in the A horizon is fundamental in soil science and land management practices.