Most gardeners think that soil tests are done only to find out what nutrients are deficient. However, it is just as important to know if you have adequate levels of nutrients so you don’t add unneeded fertilizer. The most basic soil test checks pH and the levels of phosphorus and potassium. Most of the lawn and garden soil tests that come out of our soil-testing lab show more than adequate levels of both phosphorus and potassium. If those nutrients are not needed, applying them is a waste of money and can be a source of pollution. In extreme cases, excess phosphorus can interfere with the uptake of micronutrients. So, if you haven’t taken a soil test in several years, take one this spring.
Begin by taking a representative sample from a number of locations in the garden or lawn that goes from the surface to 6 to 8 inches deep. Mix the samples together in a clean container and select about 1 pint of soil. For more detail on taking a soil test, see http://www.agronomy.ksu.edu/soiltesting/p.aspx?tabid=40. Take the soil to your local K-State Research and Extension office to have tests done at the K-State soil-testing laboratory for a small fee. A soil test determines fertility problems, not other conditions that may exist such as poor drainage, poor soil structure, soil borne diseases or insects, chemical contaminants or damage, or shade with root competition from other plants (see accompanying article). All of these conditions may reduce plant performance but cannot be evaluated by a soil test. (Ward Upham)