Topsoil is generally the top 2 inches of soil and is composed of the heaviest concentration of microorganisms and organic matter. Topsoil is vital because plants get the majority of their nutrients from it, and plants' roots are generally concentrated within it. It is sometimes referred to as the "A Horizon."
Topsoil, the uppermost layer of soil, tends to not go any deeper than 8 inches. It's a blend of humus (decaying organic material) with composted material and minerals, which produce a healthy substrate for both trees and plants.
Topsoil is a highly valuable resource for nutrients, which is why its conservation is so crucial. Modern farming utilizes crop rotation in order to maintain topsoil and encourage soil health. Crop rotation, unlike repeatedly planting the same plants over and over, doesn't deplete the nutritious value of topsoil.
Healthy vs. Unhealthy
It is important to be able to spot the visual differences between healthy and unhealthy topsoil. Healthy topsoil is moist and has a crumbly texture and a rich, dark brown color. Unhealthy topsoil has a thin, uniform texture and is light gray.
Severe water runoff can destroy topsoil or cause it to disappear entirely. This is particularly problematic over clear-cut land, because there aren't any plants and trees to sustain valuable topsoil. Heavy storms drag an abundance of topsoil into watersheds, clogging rivers and driving the fish out.
Improper farming practices that are not environmentally conscious can slowly destroy topsoil forever. In many parts of the American Midwest, Australia and Africa, farmers must operate with reduced topsoil and use more fertilizers. This results in the degradation of the existing topsoil, which makes it necessary to utilize more complex practices to bring back the healthy balance of nutrients.