Interactions of Nitrogen, Weather, Soil, and Irrigation on Corn Yield

Numerous factors that affect corn yield in the Northern Great Plains are not considered in current N fertilizer recommendations. A linear model to describe the interactions of N fertility, weather, soil, and irrigation on corn (Zea mays L.) yield was developed for a 6-yr field study in southeastern North Dakota. Varying rates of postemergence fertilizer N were applied to plots in four quadrants of a sprinklerirrigated field. Four irrigation-scheduling methods varied by year (Y) and quadrant (Q). Grain yield, stover yield, and N uptake response to a covariate (soil N plus starter fertilizer N), N treatment (Nt), Q, Y, irrigation treatment (I), previous irrigation treatment (P), and the two-way interactions that included Nt, were investigated using standard regression techniques. Yield increased significantly with Nt up to a rate of 135 kg N ha^-1 for most Y, Q, and I. Average yearly yield was adversely affected by cool climatic conditions in 2 yr. Soil conditions in two quadrants resulted in a 1.25 Mg ha^-1 average annual yield reduction compared with the other quadrants. An irrigation scheduling method utilizing a water balance algorithm resulted in higher yields compared with the other scheduling methods. The interactions of Nt with Q, Y, and I were significant. Optimized total N rates (the sum of soil nitrate N, starter N, and postemergence Nt) derived from quadratic-linear plateau analysis varied (232-374 kg N ha^-1) with Y, Q, and I and averaged 295 kg N ha^-1. Soil properties, soil moisture availability, and yearly climatic factors should be considered when making fertilizer recommendations.