Potassium is important for crop production in Wisconsin particularly in rotations with alfalfa and corn silage. Unfortunately when potash prices increased dramatically in 2008 many growers chose not to apply potash or apply less than recommended rates. Recently, soil test K levels have been decreasing throughout much of Wisconsin even before potash prices increased (Fig. 1). Though changes in soil test K over time vary by county (Fig. 2).
Soil Science Extension
University of Wisconsin Madison