1. Recalibration of Potassium Requirements for Corn in North Dakota

The previous North Dakota potassium recommendations for corn were borrowed from central Corn Belt states, where the dry soil-based 1 M ammonium acetate extraction for soil test K was utilized with a critical K value of 150 ppm. This value was adequate before 2000 because corn production was limited to only a few counties in southeastern North Dakota, and soil test K values were commonly above 300 ppm. However, the intensification of corn production in these counties and an increasing acreage around... D. Franzen, J. Breker, M. Rakkar, A. Chatterjee