Texas FFA Nursery Landscape Practice Exam

The three major divisions of a soil profile are:

1. Topsoil, subsoil, and parent material

2. Mulch, clay, and parent material

3. Topsoil, clay layer, and rock layer

4. Topsoil, subsoil, and bedrock

The correct answer is: Topsoil, subsoil, and parent material

The correct response identifies the three major divisions of a soil profile accurately as topsoil, subsoil, and parent material. Topsoil, generally rich in organic matter and nutrients, is the uppermost layer that supports plant growth. Below it lies the subsoil, which is denser and typically contains less organic matter, serving as a zone where water and nutrients percolate down from the topsoil. Parent material is found beneath the subsoil and consists of the weathered rock and minerals from which the soil is formed. This structure reflects how soils develop, layer by layer, influencing their characteristics and the types of vegetation that can thrive in them. The other choices incorporate elements that either misrepresent soil layers or introduce layers that do not correspond to the established understanding of a soil profile. For example, terms like "mulch" and "clay layer" refer more to surface materials and specific types of soil texture, rather than the fundamental divisions that comprise a soil profile. Bedrock is often seen as a foundation beneath parent material, but it isn’t categorized as a separate division in the context of soil profiles. Hence, the first choice remains the most accurate description of a soil profile's major divisions.