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Closing the N‑Use Efficiency Gap to Achieve Food and Environmental Security

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journal contribution
posted on 20.05.2014, 00:00 authored by Zhenling Cui, Guiliang Wang, Shanchao Yue, Liang Wu, Weifeng Zhang, Fusuo Zhang, Xinping Chen
To achieve food and environmental security, closing the gap between actual and attainable N-use efficiency should be as important as closing yield gaps. Using a meta-analysis of 205 published studies from 317 study sites, including 1332 observations from rice, wheat, and maize system in China, reactive N (Nr) losses, and total N2O emissions from N fertilization both increased exponentially with increasing N application rate. On the basis of the N loss response curves from the literature meta-analysis, the direct N2O emission, NH3 volatilization, N leaching, and N runoff, and total N2O emission (direct + indirect) were calculated using information from the survey of farmers. The PFP-N (kilogram of harvested product per kilogram of N applied (kg (kg of N)−1)) for 6259 farmers were relative low with only 37, 23, and 32 kg (kg of N)−1 for rice, wheat, and maize systems, respectively. In comparison, the PFP-N for highest yield and PFP-N group (refers to fields where the PFP-N was within the 80–100th percentile among those fields that achieved yields within the 80–100th percentile) averaged 62, 42, and 53 kg (kg of N)−1 for rice, wheat, and maize systems, respectively. The corresponding grain yield would increase by 1.6–2.3 Mg ha–1, while the N application rate would be reduced by 56–100 kg of N ha–1 from average farmer field to highest yield and PFP-N group. In return, the Nr loss intensity (4–11 kg of N (Mg of grain)−1) and total N2O emission intensity (0.15–0.29 kg of N (Mg of grain)−1) would both be reduced significantly as compared to current agricultural practices. In many circumstances, closing the PFP-N gap in intensive cropping systems is compatible with increased crop productivity and reductions in both Nr losses and total N2O emissions.