Soil Testing

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. Soil characteristics can vary significantly from one spot to

another, even in a small garden or field. Taking samples everywhere in the field is crucial to get the most accurate measurement of nutrients and other organisms. An example of this is along gravel roads where the soil could have more lime from the dust from the roads settling down in the soil, or an old animal feedlot where phosphorus and nitrogen counts could be higher than the rest of the field.

Sample depth is also an important factor. It is recommended that you take the samples from tillage depth, as this is where the majority of the nutrients and elements are placed mechanically. The presence of various nutrients and other soil components varies during the year, so sample timing may also be important.

Sampling and testing in the fall is beneficial because the producer will get the results back in time to formulate the fertilizer plan for the following growing season. Another time sampling and testing can be done is spring. This is a good way to see what nutrients survive over winter when the soil freezes, as well as if any leaches away from melting of snow and thawing of the soil. This way the producer can know if more or less fertilizer needs to be purchased.

Mixing soil from several locations to create an “average” (or “composite”) sample is a common procedure but it must be used judiciously as it can artificially dilute quantities/concentrations of soil components and may not meet government agency requirements for sampling. Make a reference map for your filing system so you know where you took them, and how many samples you took in the field. All of these considerations affect the interpretation of test results.

Tests include, but aren’t limited to, major nutrients – nitrogen (N), phosphorus (P), and potassium (K), secondary nutrients – sulphur, calcium, magnesium, minor nutrients – iron, manganese, copper, zinc, boron, molybdenum, aluminum.

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. (WIKIPEDIA, Soil Testing, 11-19-10)