title: Nitrogen use efficiency in grain production and the estimated nitrogen input/output balance in China agriculture.
abstract: BACKGROUND
  Understanding the nitrogen (N) use efficiency and N input/output balance in the agricultural system is crucial for best management of N fertilisers in China.
  
  
  RESULTS
  In the last 60 years, N fertiliser consumption correlated positively with grain production. During that period the partial factor productivity of N (PFPN ) declined greatly from more than 1000 kg grain kg⁻¹ N in the 1950s to nearly 30 kg grain kg⁻¹ N in 2008. This change in PFPN could be largely explained by the increase in N rate. The average agronomic efficiency of fertiliser N (AEN ) for rice, wheat and maize during 2000-2010 was 12.6, 8.3 and 11.5 kg kg⁻¹ respectively, which was similar to that in the early 1980s but lower than that in the early 1960s. Estimation based on statistical data showed that a total of 49.16 × 10⁶ t of N was input into Chinese agriculture, of which chemical N, organic fertiliser N, biological fixed N and other sources accounted for 58.2, 24.3, 10.5 and 7.0% respectively. Nitrogen was surplus in all regions, the total N surplus being 10.6 × 10⁶ t (60.6 kg ha⁻¹).
  
  
  CONCLUSIONS
  The great challenge is to balance the use of current N fertilisers between regions and crops to improve N use efficiency while maintaining or increasing crop production under the high-intensity agricultural system of China.
authors.affiliation: International Plant Nutrition Institute (IPNI) China Program and Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, 12 South Zhongguancun Street, Beijing 100081, China. sli@ipni.net
authors.forename: Shutian
authors.initials: S
authors.lastname: Li
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.forename: Jiyun
authors.initials: J
authors.lastname: Jin
mesh_terms: D000383:Agriculture / Q000639:trends; D002681:China; D018556:Crops, Agricultural / Q000254:growth & development* / Q000378:metabolism*; D002523:Edible Grain / Q000254:growth & development* / Q000378:metabolism*; D005308:Fertilizers / Q000032:analysis*; D008372:Manure / Q000032:analysis; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D058871:Organic Agriculture / Q000639:trends; D012275:Oryza / Q000254:growth & development / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D062211:Spatio-Temporal Analysis; D014908:Triticum / Q000254:growth & development / Q000378:metabolism; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism
chemical_list: D005308:Fertilizers; D008372:Manure; D012987:Soil; D009584:Nitrogen