Effect of Long-term Nitrogen, Phosphorus and Potassium Fertilization of Irrigated Corn and Grain Sorghum

Long term research shows that phosphorus and nitrogen fertilizer must be applied for optimum grain yields of irrigated corn and grain sorghum in western Kansas. In this study, the optimum economic N rate (with P) for corn remains relatively constant at about 160 lb N/acre. Application of the economic optimal N rate does not enhance the potential for nitrate leaching. Fertilizer P at 40 lb P₂O₅/acre appears to be adequate for producing optimum grain yield of corn. KS-23F