A soil test will help you if you are putting in a new garden or trying to solve soil problems in an established one. It will give you precise information about your soil, and a soil testing laboratory will probably tell you how to correct any problems, too.
You can test your soil yourself with a soil test kit, or send a sample into a soil test laboratory for analysis
Soil Test Kits
Kits that let you make your own soil tests are available at most garden centers and from many gardening web sites. These work pretty well for pH tests, but require some care and skill to get accurate measurements of nutrients.
Most of these kits have you add one or more liquids to a soil sample in a test tube, then compare the resulting color with a chart. Because nutrient availability depends on a complex of chemical factors, the tests don’t always reflect their availability in your soil. The pH level is more straightforward, and kits do a reasonable job of measuring it.
Soil Test Laboratories
In many states, soil is tested for free or for a nominal fee by the state agricultural school. If you are not in one of those states, use a commercial testing laboratory. For more information, see Soil Testing Laboratories.
The accuracy of a soil test depends on getting a good soil sample to test. For instructions, see Taking a Soil Sample.