Final answer:
The topsoil layer in a soil profile called the A horizon has been cultivated in conventional agriculture. The B horizon is the subsoil layer, made up of material that has migrated from the topsoil.
Step-by-step explanation:
The topsoil in a soil profile is referred to as the A horizon. This layer is a mixture of organic material with inorganic products of weathering. The topsoil has been cultivated for agricultural use, indicating the land has undergone processes such as plowing and planting, which are characteristic of conventional agriculture. The B horizon, on the other hand, is considered the subsoil, where there is an accumulation of mostly fine material that has moved downward from the A horizon.
It's important to note that the thickness and composition of these horizons can vary greatly based on factors such as parent material, climate, topography, biological factors, and time. In the context of a cultivated soil profile, you may also come across tilling, which is indicative of conventional agriculture as opposed to sustainable agriculture methods.