|Title||Nitrogen Surplus Benchmarks for Controlling N Pollution in the Main Cropping Systems of China|
|Author(s)||Zhang, Chong; Ju, Xiaotang; Powlson, David; Oenema, Oene; Smith, Pete|
|Source||Environmental Science and Technology 53 (2019)12. - ISSN 0013-936X - p. 6678 - 6687.|
Sustainable Soil Use
|Publication type||Refereed Article in a scientific journal|
Nitrogen (N) surplus is a useful indicator for improving agricultural N management and controlling N pollution. Few studies have developed benchmark values for cropping systems in China, a country with the largest N fertilizer use in the world. We established N surplus benchmarks for 13 main cropping systems, at optimal N management, using results from >4500 on-farm field experiments and a soil surface balance approach. These cropping systems accounted for about 50% of total N fertilizer consumption in Chinese agriculture in 2009. The results showed that N surplus benchmarks for single cropping systems ranged from 40 to 100 kg N ha-1 yr-1 (average 73 kg N ha-1 yr-1), and for double cropping systems from 110 to 190 kg N ha-1 yr-1 (average 160 kg N ha-1 yr-1), roughly twice that of single cropping systems. These N surplus benchmarks may be further refined, following further decreases in N deposition rates and reactive N losses as a result of strict implementation of "4R-nutrient stewardship" and improvements in fertilization techniques and agronomic managements. Our N surplus benchmarks could serve as realistic targets to improve the N management of current conventional practices, and thereby could lay the foundations for a more sustainable N management in China.