Late-Season Nitrogen Fertilizer Application in Soybean

Field experiments were conducted at the North Central Kansas Experiment Field near Scandia, KS, in the summer of 2014 to evaluate effect of late-season nitrogen (N) fertilizer application on modern soybean genotypes under dryland and irrigated environments. The main objective was to determine if the N application late in the season has an agronomical benefit to soybean producers. A unique fertilizer N source (urea) was applied at five N rates (0, 40, 80, 120, and 160 lb N/a) to soybean at the R3 growth stage. Overall soybean yields under dryland conditions ranged from 73 to 89 bu/a, whereas yield variation in the irrigated environment was narrowed and ranged from 90 to 99 bu/a. Application of late-season N fertilizer did not significantly increase soybean yields either under full irrigation or in the dryland environment. Under irrigation, maximum soybean yield was documented at 99 bu/a with the 0-N fertilizer rate, whereas dryland soybean yield was maximized at 89 bu/a with 120 lb N/a