Changes in agricultural practices could reduce soil emissions of nitrous oxide (N2O) and nitric oxide (NO), according to a new study by scientists at Chengdu Institute of Biology, Chinese Academy of Sciences and the University of California, Davis.
Nitrous oxide is a greenhouse gas and destroys the ozone layer that shields Earth from ultraviolet light high in the atmosphere. Nitric oxide is key to atmospheric photochemistry and air quality. Agriculture and the use of nitrogen-based fertilizer are a major source of atmospheric N2O and NO, which are produced through microbial and abiotic chemical reactions.
Prof. WU Ning and Dr. ZHU Xia from Chengdu Institute of Biology studied N2O and NO production from three different soil types fertilized with urea or ammonium sulfate under different oxygen concentrations. By labeling 15N in ammonium (NH4+) and nitrate (NO3-), 18O in H2O and NO3-, they distinguished N2O produced from different pathways, and found that low oxygen concentrations yielded more N2O and NO from ammonia oxidation pathways.
In this process, the opposite of what researchers previously believed based on indirect measures of oxygen was proved availability. Urea fertilizer also produced more N2O and NO. The results indicate that fertilizer choice and agricultural practices to promote soil aeration can reduce emissions.
The study’s other co-authors include UC Davis Department of Land, Air and Water Resources Professor William R Horwath, researchers Martin Burger and Timothy Doane. Funding for the study was provided through the J.G. Boswell Endowed Chair in Soil Science at UC Davis.
This paper entitled “Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability” was published online in Proc. Nat. Acad. Sci. USA, DOI: 10.1073/pnas.1219993110.
Full Text Link: Source of Greenhouse Gas Emissions from Agricultural Soil Underestimated---Chinese Academy Of Sciences