Production System Techniques to Increase Nitrogen Use Efficiency in Winter Wheat*

Abstract

ABSTRACT Most current research on winter wheat (Triticum aestivum L.) focuses on increasing yields of either grain or plant biomass. Increased production costs and environmental awareness will promote the development of methods to increase the efficiency of applied nutrients. Nitrogen (N) is often the most limiting nutrient for cereal grain production and represents one of the highest input costs in agricultural systems. This study was conducted to evaluate the effects of several short-term practices on nitrogen use efficiency (NUE) in winter wheat at three locations in Oklahoma. The variables evaluated included variety, nitrogen source, nitrogen timing, nitrogen rate, production system (forage only vs. grain only and a combination of the two), resolution of nitrogen application based on in-season estimated yield (INSEY), and application of a late-season senescence delaying chemical and late-season KH2PO4. Results indicate that many approaches can be taken to increase NUE in wheat production systems. Averaged over 9 site yrs, the highest NUE was for forage-only production systems (66% for “Jagger” and 52% for “2174”) far higher than grain-only production systems (26% for “Jagger” and 37% for “2174”). The combination of a 3-way split application using sensor measurements and 1 m2 application resolution produced the highest average grain-only NUE at 81% for 2174 and 48% for Jagger compared with 29% NUE for pre-plant applied N. The most critical components of NUE from this study appear to be production system, variety, N fertilizer timing, and INSEY based topdress N applications.