Extractable K in Kansas Soils: Effects of Soil Moisture and Drying Conditions.

Potassium (K) is an essential nutrient for plant development, and in recent years, an increasingly expensive fertilizer input—thus increasing the importance of accurate soil test results in making agronomically and economically prudent nutrient management decisions. In parts of southeast Kansas, soil K test results have shown inexplicable swings from year to year and have been poorly correlated with fertilizer response. To determine whether or not the processing procedure for soil testing laboratories influences extractable K results, the effects of drying time, drying temperature, soil moisture content, and wetting-drying cycles were studied. Soil samples from four southeast Kansas sites exhibiting unusual K behavior and three northeastern Kansas sites with more typical behavior were subjected to a variety of drying time, drying temperature, and moisture conditions and then extracted with 1M ammonium acetate. The results indicate negligible effect of drying time, temperature, and moisture conditions on extractable K values.