A corn crop takes up nearly as much potassium (K) as it does nitrogen (N), yet management of each nutrient is entirely different. Whereas harvesting 125 bushels of corn grain per acre removes only 35 lbs of potash (K₂O), harvesting 21 tons of silage per acre carries away 160 lbs of K₂O; and the voracious appetite of a 5-ton per-acre alfalfa crop takes 230 lbs of K₂O per acre from a field. Yet, managing potassium for each of these crops is relatively simple because of the reaction of K with soil, a reaction completely unlike the behavior of N in soil.

soil test recommendation tables based on field research data obtained in North Dakota, South Dakota, western Minnesota and the Canadian Prairie Provinces