Aerating Soil Yields Cleaner Air

Aerating soil could become a key strategy for reducing agricultural emissions of atmosphere-damaging nitrogen oxides, according to a research team led by William R. Horwath of the University of California, Davis (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1219993110). Nitric oxide (NO) leads to health-harming ground-level ozone, and nitrous oxide (N₂O) is a greenhouse gas. Nitrogen-based fertilizers are a major source of atmospheric NO and N₂O, which are produced primarily through microbial activity. Horwath and colleagues studied production of the compounds from three soil types fertilized with urea or ammonium sulfate under different oxygen concentrations. They found that lower oxygen levels yield more NO and N₂O, the opposite of what researchers previously believed on the basis of indirect measures of oxygen availability. Urea fertilizer in particular produces more NO and N₂O. The results indicate that fertilizer choice and agricultural practices to promote soil aeration could help reduce emissions of the pollutants.