Improving nitrogen management via a regional management plan for Chinese rice production

摘要

A lack of basic information on optimal nitrogen (N) management often results in over- or under-application of N fertilizer in small-scale intensive rice farming. Here, we present a new database of N input from a survey of 6611 small-scale rice farmers and rice yield in response to added N in 1177 experimental on-farm tests across eight agroecological subregions of China. This database enables us to evaluate N management by farmers and develop an optimal approach to regional N management. We also investigated grain yield, N application rate, and estimated greenhouse gas (GHG) emissions in comparison to N application and farming practices. Across all farmers, the average N application rate, weighted by the area of rice production in each subregion, was 210 kg ha?1 and ranged from 30 to 744 kg ha?1 across fields and from 131 to 316 kg ha?1 across regions. The regionally optimal N rate (RONR) determined from the experiments averaged 167 kg ha?1 and varied from 114 to 224 kg N ha?1 for the different regions. If these RONR were widely adopted in China, approximately 56% of farms would reduce their use of N fertilizer, and approximately 33% would increase their use of N fertilizer. As a result, grain yield would increase by 7.4% from 7.14 to 7.67 Mg ha?1, and the estimated GHG emissions would be reduced by 11.1% from 1390 to 1236 kg carbon dioxide (CO2) eq Mg?1 grain. These results suggest that to achieve the goals of improvement in regional yield and sustainable environmental development, regional N use should be optimized among N-poor and N-rich farms and regions in China.