In agriculture, a soil test is the analysis of a soil sample to determine nutrient content, composition and other characteristics, including contaminants. Tests are usually performed to measure fertility and indicate deficiencies that need to be remedied.

The quality of the original soil sample plays a key role in determining the practical value of test results. Most labs will provide documentation outlining the proper procedures for collecting soil samples.

Soil testing is often performed by commercial labs that offer an extensive array of specific tests. Choosing the test lab site is just as important as the test results. There are many soil testing labs in the United States, but finding the right one for you will take some research. It is most beneficial for the producer to find the local most lab, as the workers will have a greater knowledge and more experience working with the local soils.

Tests include, but aren't limited to, major nutrients - nitrogen (N), phosphorus (P), and potassium (K), secondary nutrients - sulfur, calcium, magnesium, minor nutrients - iron, manganese, copper, zinc, boron, molybdenum, aluminum, physical properties - soil acidity, electrical conductivity, soil organic matter, moisture content, and soil contaminants (e.g., fuel components such as benzene, toluene, xylene, petroleum hydrocarbons).

Soil testing can be an easy, cost effective way to manage agronomic as well as horticultural soils. It tells key nutrient levels, as well as pH levels, so the producer can make the best choice when purchasing fertilizers and other nutrients.

Less comprehensive do-it-yourself kits are also available, usually with tests for three important plant nutrients - nitrogen (N), phosphorus (P), and potassium (K) - and for soil acidity (pH). Do-it-yourself kits can usually be purchased at your local cooperative or through the university or private lab you choose. Prices of the tests will vary on the lab/university you purchase it from and also on what kind of test you want to do. Lab tests are more accurate, though both types are useful. In addition, lab tests frequently include professional interpretation of results and recommendations. Always refer to all proviso statements included in a lab report - these may outline any anomalies, exceptions and shortcomings in the sampling and/or analytical process/results.

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)