Location: Soil and Water Management ResearchTitle: Nitrogen management and air quality in China
|GRIFFIS, T - University Of Minnesota|
Submitted to: Nature Food
Publication Type: Review Article
Publication Acceptance Date: 9/11/2020
Publication Date: 10/14/2020
Citation: Griffis, T.J., Baker, J.M. 2020. Nitrogen management and air quality in China. Nature Food. 1:597-598. https://doi.org/10.1038/s43016-020-00167-8.
Technical Abstract: Global demand for fertilizer N now exceeds 110 Tg per year, and is steadily increasing. But the dramatic N-fueled surge in crop production has had some decidedly negative environmental consequences. Nitrogen fertilizer is produced in either oxidized (nitrate-based) or reduced (ammonia-based) forms. Once they have been applied, N fertilizers are quite reactive, subject to further biotic and abiotic transformations that result in the release of a variety of N compounds. Due to these transformations, in concert with the tendency of many farmers to apply N in excess of crop needs, global nitrogen use efficiency (NUE) is remarkably low (~40%). Consequently, a significant fraction of the applied synthetic N leaks out of agricultural systems as highly reactive compounds that are detrimental to water resources, ecosystem health, and the atmosphere’s composition and function. In the United States alone, health costs associated with agricultural NH3 are estimated at $36 billion (2006 USD) annually despite a national NUE that has varied from about 0.6 to 0.7 since 1960. The NUE in China has declined from about 0.65 in 1960 to a current estimate of 0.387. Thus, the reactive nitrogen leakage rate is nearly 2 times greater in China, and environmental and health consequences have been severe, with PM2.5 alone associated with 1.3 million pre-mature deaths each year. Guo et al provide a comprehensive analysis of mitigation strategies designed to reduce reactive N leakage from agricultural systems in China. They combined extensive agricultural research datasets, meta-analyses, and chemical transport modeling to evaluate how practical N mitigation efforts (i.e. reduced N fertilizer application, deep placement of N fertilizer, enhanced-efficiency N fertilizers, and improved manure N management) impacted greenhouse gas emissions, NH3 emissions, and PM2.5 formation, water pollution, and NUE and crop yields. Such syntheses are critical for diagnosing reactive N leakage because these systems are complex, with several potential transformation pathways, tradeoffs, and unintended consequences that must be considered when guiding the development of policy.