The layer of soil that determines how fertile it is would be the topsoil. To determine this answer, you can refer to the layers of soil composition. The different layers of soil include topsoil, subsoil, and bedrock. In this case, the topsoil is responsible for the majority of the soil's fertility. It is the uppermost layer of soil and typically contains a high amount of organic matter, such as decomposed plant and animal material known as humus. This layer is rich in nutrients and microorganisms, making it conducive for plant growth. Therefore, the correct answer would be topsoil.
The layer of soil that determines how fertile the soil is is called topsoil.
