What is the organic layer of soil called?

The organic layer of soil is called the O horizon. This layer is primarily composed of organic matter such as decomposed leaves, plant materials, and other organic debris, which contributes to the soil's nutrient content and overall health. The O horizon is crucial for soil fertility and plays a significant role in the ecosystem by providing a habitat for a variety of organisms and promoting nutrient cycling.

In contrast, the other layers mentioned in the choices serve different functions: the A horizon, or topsoil, contains a mix of organic material and minerals and is essential for plant growth; the B horizon, known as subsoil, is where minerals leach from the upper layers and accumulate; and the C horizon consists of weathered rock and soil parent material. Each of these layers plays a unique role within the soil profile, but the O horizon is specifically identified for its rich organic content.