This is especially true of sandy and clay soils. Organic matter helps sandy soils hold water and nutrients. It provides clay soils with more air spaces so that roots can breathe more easily. Some plants, such as blueberries, prefer an acid soil, but generally a pH of 6 to 7 is ideal for most plants. A soil test kit purchased from a garden center will help determine soil acidity.
More detailed soil analyses to determine fertilizer requirements also are helpful.
A list of soil testing laboratories is available at your local Extension office. It is important that plants be adequately, yet not excessively, fertilized. Improper fertilization will make plants too weak or too vigorous and more subject to disease. There are several other factors to consider as you plan your garden. To prevent the buildup of disease organisms, rotate your crops from year to year on a 4-year rotation.