Yield-scaled N2O emissions in a winter wheat–summer corn double-cropping system

Emissions of nitrous oxide (N2O) from agricultural soils contribute to global warming and stratospheric ozone depletion. Applications of fertilizer nitrogen (N) increase N2O emission, but also increase agricultural production. Here, we report on the responses of crop yield, N2O emission and yield-scaled N2O emission (N2O emission per unit N uptake by grain and aboveground biomass) to different N fertilizer rates in a winter wheat–summer corn double-cropping system in the North China Plain. Soil N2O emission measurements were carried out for two years in a long-term field experiment, under semi-arid conditions with four flood irrigations events per year. Our results indicated that N2O emissions were linear functions and yield-scaled N2O emissions were cubic functions of N fertilizer application rate. Yield-scaled N2O emissions were lowest at application rates of 136 kg N ha−1 yr−1. Using a quadratic-plateau model, it was found that maximal crop yields were achieved at an application rate of 317 kg N ha−1 yr−1, which is 20% less than current practice. This level is suggested to be a compromise between achieving food security and mitigation N2O emissions.