irrigated corn, nitrogen and phosphorus fertilization, southwest Kansas


Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated corn in western Kansas. In 2014, N applied alone increased yields 58 bu/a, whereas P applied alone increased yields only 12 bu/a. Nitrogen and P applied together increased yields up to 152 bu/a. This is slightly above the 10-year average, where N and P fertilization increased corn yields up to 146 bu/a. Application of 120 lb/a N (with P) produced about 91% of maximum yield in 2014, which was similar to the 10-year average. Application of 80 instead of 40 lb P2O5/a increased average yields 9 bu/a.