Chemical and Biological Sources of Nitrogen Oxide in Swine Waste Amended Soils
Nitric oxide (NO) from abiotic and biotic processes is examined through the experimental measurement of NO flux from autoclaved and non-sterilized garden soil sampled from Sarah B. Duke Gardens, Durham, North Carolina. The biological nitrifier activity is examined using nitrapyrin treatment as an autotrophic nitrification inhibitor. NO emissions comprise an important fraction of unaccounted nitrogen movement from soil to lower levels of the troposphere. Particularly, agricultural soils are a major contributor of atmospheric nitrogen in the form of NO in rural areas. In several ways NO is a missing link for understanding nitrogen cycling globally, as NO is an important constituent in various global change models including ozone formation and accumulation in the lower troposphere. Results from this study indicate microbial nitrifier activity in aerobic garden soil as the primary source of NO. Mean NO emissions were reduced from 7.23 to 1.16 ng N/m 2s, 2.7 to 0.63 ng N/m 2s, and 4.18 to 0.47 ng N/m 2s following nitrapyrin treatment of non-amended, water amended, and waste amended soil, respectively. Preliminary findings also suggest denitrifier activity as a negligible contributor to NO flux based on the lack of response following nitrogen/waste addition to nitrapyrin treated soil as compared with non-treated test soil. Further research should investigate the role of these contributors with respect to changing soil parameters and ambient conditions.
