What layer of soil typically has the highest concentration of organic material?

The A Horizon, also known as the topsoil layer, is characterized by a high concentration of organic material. This is where most of the biological activity occurs, as it contains decomposed plant and animal matter, making it rich in nutrients. The organic matter in this layer supports microorganisms and various soil fauna, which contribute to soil fertility and overall ecosystem health.

In contrast, other layers such as the B Horizon primarily accumulate minerals leached from the upper layers, while the C Horizon consists of weathered rock and has significantly less organic content. The Subsoil, located below the A and B Horizons, may contain some nutrients but does not have the same level of organic material as the A Horizon. Therefore, the A Horizon stands out as the layer with the highest organic concentration, facilitating plant growth and contributing to soil structure and fertility.