What Is Topsoil? Topsoil is the topmost layer of soil, in most cases the top 2 to 8 inches. It has the highest concentration of organic growing materials of all soils and is where the majority of growing of plants and crops occurs.
Topsoil has been created over millions of years by chemical and physical action of weather and climate conditions. The decaying of organic matter is a big part of the mix derived by the decaying of plants and other organic materials.
Most of the nutrients and nourishment occurs in this layer where plants concentrate their roots. The depth of this layer actually is measured from the top of the ground on the surface down to the subsoil, which is the first hard packed layer below.
There is serious concern that much of the topsoil is eroding away from rainstorms, floods, and wind. Without the fertile layer of topsoil, significant plant life is impossible. It is estimated that the costs yearly from topsoil erosion at $45 million annually.
Current agriculture techniques exacerbate the depletion of topsoil because of replowing and replanting each year. The strategy of planting cover crops in order to build up the soil has some positive effect, but topsoil is still lost. Three tons per acre of topsoil is lost each year in the United States.
This rapid loss of the topsoil has left great concern among environmentalists, as it takes 500 years to form one inch of topsoil. At the current rate of depletion, there about 60 years of topsoil left.
Extra topsoil is needed for gardens and lawns, and is added to the top, then mixed in to the more sandy loam underneath. Today there are mixes of topsoil comprising of sand, subsoils, manures, and biosolids. The mix can vary but that is the basic material list.
A topsoil that is of good quality will have an open and loose structure that will have good drainage capabilities. Simultaneously, it must retain enough moisture to have available for the roots of the plants. Any mix that is added to a soil that is destined to grow plants should always be mixed with the native soil below. This insures that the water will drain properly and not get boggy.
The ideal soil described as topsoil is usually rich organically, slightly acid to slightly alkaline, sandy loam that is fertile, and free from contamination. It needs to be easy to work and available all year long. It is the ingredient that will make or break a garden and will grow plants very rapidly.
The topmost layer of soil is the thin layer at the very top, and is made up almost entirely of organic matter. Bugs, worms, bacteria and fungi are constantly digesting organic materials and transforming it into a rich humus. Over a long time, this material slowly incorporates itself into the soil below.
This process continues, and takes a very long time. Humans can accelerate this process by adding mulch or finished humus in the form of compost that is mature.
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