In an undisturbed area, topsoil can be as much as 8 inches or more deep. Unfortunately, the topsoil in many typical yards has been stripped away or damaged during construction. Other areas may have adequate topsoil, but the composition may have too much clay or sand to be effective in growing plants.
Topsoil and compost, working together, can create even more topsoil, repair the existing damaged soil and help both clay and sandy soil be more productive.
How Topsoil Is Created
Topsoil is created by the basic nature of the dirt, the action of the elements on the soil, the decay of organic material within the soil and the life of the micro-fauna inhabitants.
The best topsoil is a relatively even mixture of sand and clay. Water and the sun’s heat all act upon the soil over the decades, gradually compacting it and breaking it down over and over. Organic matter from plants and animals is constantly decaying, adding material that supports micro-fauna and other creatures such as worms. They, in turn, add their own waste material to the soil.
How Compost Is Created
Compost, in contrast, is a willful effort to specifically speed up the decaying of organic material by mixing together the necessary ingredients of plants and other organic material. With the right combination of about two parts of organic material such as leaves or straw that is heavily carbon based to one part of material such as grass, manure or kitchen wastes, compost can be created in a few weeks. Although it looks similar to soil when finished, it lacks many minerals found in soil, and the structure of soil.
How They Work Together
Topsoil provides a home for millions of micro-fauna and soil animals such as worms that, in turn, provide many necessary benefits to growing plants. Adding compost to the soil is similar to providing a banquet to a starving community.
The microorganisms break down the compost even further, feeding from the nitrogen, potassium, phosphorus and other minerals. When the short-lived micro-fauna die, this material is left in a state that is readily absorbed by plant roots. Worms do a similar job by eating their way through the material and excreting it as a supercharged food for plants.
Topsoil Without Compost
Topsoil without sufficient decaying organic material is nutritionally poor and can have problems with water and air flow. Heavy clay soil keeps the various minerals bound tightly in a matrix, and porous sand allows them to filter out. Compost enables topsoil to have the right balance in structure that allows water to flow freely through yet be retained for further use, and to create the necessary air spaces so that plant roots can breathe.
Not all commercially bought composts are equal in value. Some cities provide compost to their residents that is of nebulous quality. If the material in the bag seems sour, full of sticks or other large debris, or is not dark and crumbly, it may be inferior. Quality compost comes from only quality ingredients and a well-maintained program. Many homeowners realize the value of making their own compost.