What is the primary component that makes up topsoil?

Topsoil is primarily composed of organic materials, which play a significant role in its structure and fertility. This organic matter includes decomposed plant and animal material, and it is crucial for supporting plant life. The presence of organic materials in topsoil enhances its ability to retain moisture, supply nutrients to plants, and improve soil structure, making it more aerated and conducive to root growth.

While mineral sediments, silt, clay, sand, and gravel are also components of topsoil, they do not make up the primary component. Organic materials are essential because they contribute to the biological activity in the soil, including the activities of various microorganisms that assist in breaking down organic matter and aiding nutrient cycling. The balance of organic materials in topsoil is what primarily defines its ability to support a diverse and healthy ecosystem.