Crop producers who continuously used ridge-till planting in a corn and soybean rotation were finding potassium (K) deficiency symptoms in corn even though the K soil test levels were high or very high. The unexpected K deficiency in corn was a concern that raised questions about managing potash in the ridge. The same potash management concerns were applicable for strip-till and no-till as well, where plant nutrients become stratified in the soil as a result of reduced tillage.

Potassium deficiency symptoms in corn that was grown in ridges were reported as early as the 1960’s in Minnesota. During the drought years of 1988- 1989 in the Midwest, deficiency symptoms in corn planted with ridge-till became more common. Field trials in Minnesota showed potash that was deep banded at 40 lb. K2O/acre in the center of the row, improved yield and K deficiency symptoms disappeared. Other studies reported corn yield response with deepbanded K2O in ridge-till systems when soil test K levels were in the range of 140 ppm. Research in Iowa (Fig. 1) showed a yield response for corn when potash was banded in the center of the ridge, but not for broadcast K2O or the check. There was no response for any treatment in soybean.