Topsoil is the most productive area of the garden. It is the place that vegetable roots spread and absorb nutrients provided by the soil. There are billions of tiny living organisms in the uppermost 8 to 12 inches of the soil that create nutrition for growing plants. Beneficial bacteria, fungi and worms are a few of the organisms that live in topsoil and cycle nutrients into plants. Maintaining healthy, productive topsoil is the focus of organic gardening techniques; there are several ways to ensure successful planting.
Check Soil Structure
Scoop up a handful of garden topsoil and let it fall through your fingers to the ground. If it is dark brownish-black and has the texture of ground coffee it is just about perfect. Topsoil that needs more organic matter is either too firm or too loose in structure. Clay-like soil does not let roots grow easily or water drain properly. Loosely structured sandy soil allows too much water drainage and roots cannot hold to soil particles. Adding organic matter improves both soil structure problems.
Compost is the best source for additional organic matter for topsoil. Compost amends both loose soil and clay soil. The biological content of compost also enriches the topsoil's productivity. A study at the University of California at Davis in 2007 showed that tomatoes grown in organically enriched topsoil had 79 percent more flavinoids than tomatoes grown in ordinary soil.
Mulch is a layer of material that is spread around plants as they grow. It helps keep topsoil cool in hot weather and warm in cold weather. A mulch layer also suppresses weeds and helps topsoil retain water. Materials that are used for mulch include dry leaves, bark chips and compost. The mulch layer can be renewed with more materials as it decays into the soil.
Healthy topsoil continually renewed with organic matter is easy to plant in. Seeds germinate and roots spread easily because the soil is nutrient-rich and has good structure. After harvest is a good time to replenish topsoil. The American Dahlia Society recommends the "no-till" method of soil replenishment that adds layer upon layer of yard clippings and compost materials to topsoil. The layers decompose and the soil absorbs their nutrients. The fibrous quality of the decaying materials helps create good soil texture. Earthworms do the tilling with this method.