Why does topsoil have a dark color?

Topsoil has a dark color primarily due to the presence of organic matter, which is decomposed plant material. Organic matter is rich in carbon, nitrogen, and other nutrients essential for plant growth. As plants grow, they absorb these nutrients from the soil, and when they die and decompose, they return them to the soil in the form of organic matter. This process, along with the accumulation of other organic materials such as animal waste, fallen leaves, and root systems, contributes to the dark coloration of topsoil.

The organic matter in topsoil also enhances its ability to hold water and retain nutrients, which further supports plant growth. The dark color of topsoil thus serves as an indicator of its fertility and overall health.