Difference between topsoil and subsoil

Subsoil is the layer of soil below the topsoil. It contains mainly sandy and clay deposits without a lot of organic matter. Although subsoil is much less fertile than topsoil, it can be amended to increase its plant-growing capacities. Subsoil is also much lighter in color and much harder to handle than topsoil. It is, however, much looser than the hardened layer of bedrock lying beneath it. One advantage that subsoil has over topsoil is that it contains few if any weed seeds because of its depth, therefore increasing its attractiveness to growers and companies that make topsoil.

Topsoil : The layer of soil closest to our feet is topsoil. Geologists refer to it as the “A” horizon, whereas subsoil is the “B” horizon. Topsoil is much more fertile than subsoil because it contains more organic matter, thus giving it a darker color. A layer of humus, which is essentially dead and decaying organic matter, sometimes covers topsoil. This humus has a number of important properties for gardeners, and, as it decays into topsoil, it creates a nutrient-rich blend of soil that gardeners and landscapers dream about. Unfortunately, being the top level of soil comes at a price. Topsoil is lost to soil erosion and poor farming practices at an alarming rate. In fact, the Green Trust organization estimated that the U.S. lost about 60 percent of its topsoil in 200 years of farming.