Managing nitrogen for sustainable wheat production

Sustainable N management in agriculturally intensive regions is critically important with respect to crop productivity, private profitability, ecological protection, and human health. This study articulates the benefits of N fertilizer use to ecological (e.g., in terms of the gross revenue from yield minus the costs of N fertilizer, eutrophication, soil acidification, and global warming) and social (e.g., in terms of the benefits of ecological systems minus the costs to human health) systems based on 156 farm sites with five different N levels. Agronomically (AOR), privately (POR), ecologically (EOR) and socially (SOR) optimized N rates were derived with the minimum N rate achieving maximum benefits from N-derived yields, private profitability, ecological and social systems. Compared with the traditional AOR and POR, use of the EOR resulted in a decrease in the N rate by 24-37%, and reduced Nr losses by 31-51% without yield losses. The SOR further decreased the N rate by 36-47%, and lowered the Nr losses by 44-60%, while decreasing the grain yield by only 4.4-4.9%. Furthermore, in groups with both high soil productivity and better management, the yield was highest with the EOR and SOR (7.72-7.86 Mg ha(-1)), and the Nr losses intensity remains low relative to other three groups. Compared with farmers' practice (n = 2938), utilizing the EOR and SOR can increase the grain yield by 10-12%, reducing Nr losses by 54-63%. N management using the EOR and SOR provides a win-win opportunity, and should be prioritized in agricultural research and practice. (C) 2017 Published by Elsevier Ltd.