Considerable research has been conducted at this farm to study potassium (K) fertilization rates and placement methods on corn and soybean grain yield, K uptake, and soil-test K values. However, no research has investigated K recycling to the soil by maturing plants and crop residue until the next crop is planted. The amount and the timing of the K recycled to the soil should have a significant impact on soil-test K values, and could explain a great deal of usually very high soil-test K temporal variability. Therefore, plots of several field K trials at this farm were used to investigate these issues.