Topsoil Vs. Garden Soil

Topsoil Definition

• As the name suggests, the term "topsoil" describes the upper layer of soil in your garden. Because this is the area where plant roots live and decomposition of dead plant and animal material occurs, topsoil can be rich in organic matter and nutrients that support healthy plant growth. Soil forms from the weathering of rocks and the breakdown of organic materials. This is an incredibly slow process --- it takes 500 years to make a single inch of topsoil --- which increases the value of good topsoil.

Properties of Soil

• Topsoil that you purchase from a garden center doesn't necessarily contain anything more than your garden soil does. In fact, in some cases, your garden soil may be better than purchased topsoil. Ideal soil contains approximately 45 percent mineral materials and 5 percent organic matter. Spaces between the soil particles account for the other half of the soil's volume, with half of this filled with water and the other half filled with air. The best garden soils contain a mixture of clay, silt and sand --- a blend called loam --- have a neutral pH and contain adequate nutrients for plant growth.

Regulatory Definition of Topsoil

• Although you may think of rich, dark, fertile soil when you hear the word "topsoil," commercial topsoil is not regulated and may contain all or none of the positive attributes described here. In some instances, commercial topsoil may contain debris or herbicide residues that can harm your plants.

Purchasing Topsoil

• When deciding whether to add commercial topsoil to your garden, you should research both your garden soil and the source of the topsoil. First, send in a soil sample from your garden for a routine soil test. Cooperative extension offices can perform soil tests or recommend a lab. The results of the soil test may help you to identify problems or deficiencies that require an easier fix than bringing in new topsoil. When selecting a topsoil, ask about the source of the soil. Topsoil taken from farmland, for example, can contain herbicides that may damage your lawn or garden. If the topsoil contains amendments, find out what has been added and how much. Ask for test data identifying the pH, texture and nutrient content of the topsoil. You should avoid soils that contain large amounts of sand or clay.