There are several issues that currently surround potassium (K) management. Awareness of them has increased in recent years as farmers and advisers have intensified their collection of field data. In particular, K management is facing many challenges under conservation tillage systems. These systems have led to stratification of soil test K, where K levels at or near the surface are significantly higher than those lower in the soil profile. Research efforts are currently trying to better our understanding of how K management may need to be altered to better fit these conservation tillage systems. This paper outlines some of the major issues currently faced.

An essential component of managing K is calculating a K budget. This budget compares the amount of K added to the amount removed by crop harvest. Potassium additions include both fertilizer and manure sources. In Wisconsin, alfalfa is often part of the crop rotation. This crop removes a significant amount of K. An example of K removal by a sequence of crops in a rotation representative of Wisconsin is shown in Table 1. This table demonstrates that alfalfa removes significantly more K per acre than does either corn or soybean. This occurs because only the grain is removed during corn and soybean harvest while most of the above-ground plant portion is removed when alfalfa is cut. When producers and advisers underestimate the amount of K removed in rotations containing alfalfa, unexpected declines in soil test K levels and associated K malnutrition problems can result.