PO 17. Indicate how the following may cause variability in soil test results.

In addition to affecting how soil samples are taken, various aspects of management can affect the results obtained from soil tests.  These should be taken into account and procedures should be observed to maximize the accuracy of samples.

Nutrient content of the soil solution and soil matrix vary depending on the time of year.  Temperature, moisture, pH, and aeration vary with the climate, and during or after the growing season, nutrient levels are affected by crop removal.  To minimize variability and build the strongest historic records, take samples at the same time each year.

Samples should be taken over a constant depth to minimize variability and build strong historic records.  The soil sample depth depends on the tillage type used (usually 6-8" deep), as lime and fertilizer are mixed in the tillage layer.  For determining lime requirements in a no-till system, take two subsamples: 0-1" and 0-6 or 8".