Coupled water and nitrogen (N) management as a key strategy for the mitigation of gaseous N losses in the Huang-Huai-Hai Plain

Gaseous nitrogen (N) losses are mainly responsible for low N use efficiency of applied fertilizers and their derivative environmental hazards, while N application rates and soil water regime are important factors regulating these N processes. In this study, gaseous N losses via ammonia volatilization (AV) and denitrification, determined by sponge trapping-KCl extraction and acetylene inhibition-soil core incubation, respectively, were investigated under different coupled water-N management practices with a winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation system in the Huang-Huai-Hai Plain. Ammonia volatilization after urea application, particularly after topdressing during maize growing seasons, was the dominant gaseous N loss, amounting up to 53.2 kg N ha−1 (38.6 % of the applied N). Ammonia volatilization generally decreased by increasing irrigation rate applied immediately after fertilization. Denitrification N losses were lower than ammonia-N losses, accounting for 1.3 to 18.7 kg N ha−1 year−1, with more than 90 % occurring during the maize growing seasons. Total gaseous N losses showed a significant (P