Soybean Yield Responds Minimally to Nitrogen Applications in Missouri

Interest among soybean ( Glycine max Merr.) producers in using nitrogen (N) fertilizer for soybean production has been stimulated by recent reports of substantial yield responses to N. We conducted 48 experiments measuring soybean yield response to N over a broad range of soils, genetics, and weather. Nitrogen fertilizer was applied either preplant or at the beginning pod stage. Minimal soybean yield response to N was found. Small responses (approx. 1 bu/acre) to N applied at planting were observed in two groups of experiments: experiments with soil salt pH < 6.0 and experiments with soil nitrate‐N < 50 lb/acre to a 2‐foot depth. Of five experiments with yields > 60 bu/acre, two responded to N at planting. No yield response to N applied at the beginning pod stage was seen for any group of experiments sharing specific soil or crop factors.