Splitting Spring Nitrogen Applications For Winter Wheat: Optimizing Yield and Profit

Our goal was to improve winter wheat (Triticum aestivum L.) N‐fertilizer recommendations made in the southeastern USA. Previous research resulted in recommendations for optimizing economic return by using whole‐plant tissue tests to determine N fertilizer rates at the end of tillering. That research also indicated that an additional earlier N application was required at spring green‐up if tiller density was low. Research upon which these latter recommendations were based is limited. Our objective was to determine optimum N‐fertilizer rates at spring green‐up to help producers determine when these additional N applications are economical. Trials were conducted in the North Carolina Piedmont, Coastal Plains, and Tidewater regions in 2002, 2003, and 2004. The amount of fertilizer N needed at spring green‐up to maximize yield and profit was dependent on tiller density. In fields with low densities, profit increased up to 12% by applying ~45 lb N per acre at spring green‐up and following that with a second application at the end of tillering, compared to applying only a single application at the end of tillering. Applying high rates of early N was detrimental to economic return when tiller densities were high. A set of recommendations for optimizing spring green‐up N fertilizer rates as a function of tiller density and economic assumptions is presented.