AP BIOLOGY

Detailed explanation-1: -This layer is rich in organic material and is known as the humus layer. This layer consists of both organic matter and other decomposed materials. The topsoil is soft and porous to hold enough air and water.

Detailed explanation-2: -The topsoil is relatively thin but it has most of the soil’s nutrients. Just below the topsoil layer is the subsoil layer. The subsoil may contain some broken down organic matter but it is mostly made of weathered rocks and clay minerals.

Detailed explanation-3: -In soil classification systems, topsoil is known as the O Horizon or A Horizon. Soil horizons are layers parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath.

Detailed explanation-4: -Topsoil is the uppermost layer of the ground, on average 2-10 inches deep, that contains most of the nutrients and fertility of the soil. In the landscaping industry, anything gathered and packaged from that layer of soil is called topsoil. The quality of it may vary, depending on where it’s harvested from.

Detailed explanation-5: -A Horizon. Most commonly called topsoil, the A horizon is a layer of mineral soil that has a defined soil structure, and it is mostly made up of humus (decayed organic matter). The A horizon may be a result of soil disturbance by plant and animal activity.