Soybean Yield Response and Distribution As Influenced By Supplemental Nitrogen Application.

Field studies were conducted in 2014 and 2015 in Stoneville, MS, to evaluate soybean aboveground biomass and grain yield response to supplemental N fertilization. Studies were carried out on two commonly cropped Mississippi soils, a silt-loam or coarser textured soil and a clay textured soil. Soybean aboveground biomass was observed to be significantly influenced by the main effects of application timing, N rate, and N source on silt-loam soils, while clay soils exhibited no response to any experimental factor influencing aboveground biomass. On silt-loam or coarser textured soils, soybean receiving N fertilization was observed to exhibit mean soybean grain yields 193 kg ha-1 greater than soybean receiving no N (0 kg N ha-1). On clay textured soil, soybean receiving N fertilization was observed to exhibit mean soybean grain yields 281 kg ha-1 greater than soybean receiving no N (0 kg N ha-1). Environmentally Smart Nitrogen was observed to produce the greatest grain yields on silt-loam soils. However, the main effect of N rate appears to be most critical factor influencing soybean grain yield across soil textures. Yield component analysis was observed to exhibit a similar trend to that of overall soybean grain yield as the main effect of N rate significantly influenced yield components, directly paralleling soybean grain yield. N fertilizer additions were able to fulfill soybean N requirement and increase the overall grain yields of the soybean plant in high yielding environments on two common Mississippi soils in the mid-south production system.