title: Closing the N-use efficiency gap to achieve food and environmental security.
abstract: 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.
authors.affiliation: Center for Resources, Environment and Food Security, China Agricultural University , Beijing, 100193, China.
authors.forename: Zhenling
authors.initials: Z
authors.lastname: Cui
authors.forename: Guiliang
authors.initials: G
authors.lastname: Wang
authors.forename: Shanchao
authors.initials: S
authors.lastname: Yue
authors.forename: Liang
authors.initials: L
authors.lastname: Wu
authors.forename: Weifeng
authors.initials: W
authors.lastname: Zhang
authors.forename: Fusuo
authors.initials: F
authors.lastname: Zhang
authors.forename: Xinping
authors.initials: X
authors.lastname: Chen
mesh_terms: D000383:Agriculture; D002681:China; D004777:Environment; D005523:Food Supply; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis; D012275:Oryza / Q000254:growth & development / Q000378:metabolism; D014908:Triticum / Q000254:growth & development / Q000378:metabolism; D014835:Volatilization; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism
chemical_list: D009609:Nitrous Oxide; D009584:Nitrogen