Submitted to: Transactions of the ASABE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/22/2012
Publication Date: 9/1/2012
Citation: Miller, J.O., Hunt, P.G., Ducey, T.F., Glaz, B.S. 2012. Denitrification and gas emissions from organic soils under different water table and flooding management. Transactions of the ASABE. 55(5):1793-1800. Interpretive Summary: Agricultural practices in the Everglades of South Florida have contributed to land subsidence and nutrient runoff. In order to mitigate these environmental problems, water is being intensively managed in the Everglades Agricultural Area. One investigated option is management of water to obtain periodically high water tables. While achieving many desired results, this management makes the soils wetter. Consequently, it increases the possibility that enhanced denitrification in these soils may emit nitrous oxide, a potent greenhouse gas. To assess the impact of the water table management, we measured gas emissions and denitrification potential from organic soils of the Everglades Agricultural Area. In this lysimeters pilot study, water table depths ranged from 40 to 80 cm. Higher water tables did not increase denitrification or nitrous oxide emissions from these soils. Thus, results from this pilot study indicate that denitrification and nitrous oxide are not likely to be negatively impacted by periodically high water tables.
Technical Abstract: Draining the Florida Everglades for agricultural use has led to land subsidence and increase phosphorus loads to the southern Everglades, environmental concerns which can be limited by controlling water table depth. The resulting anaerobic conditions in saturated soils may lead to increased denitrification and gaseous nitrous oxide release. Sugarcane was grown in lysimeters using four water table treatments, ranging from 40 to 16 cm in depth. Gas emissions were measured in April, July, and September using a photoacoustic gas analyzer. Denitrification enzyme activity was performed on soil samples from the upper 6 inches using non-limiting carbon and nitrogen conditions. No differences in nitrous oxide emissions or denitrification were observed between water table treatments. Emissions of nitrous oxide were higher in the spring though, with carbon dioxide emissions being greater in the late summer. Overall, incomplete denitrification was very low in soil samples, indicating that shallow water tables will not increase nitrous oxide emissions in these organic soils. Additions of carbon versus nitrate increased denitrification, indicating that these organic soils are carbon limited. Both amoA and nosZ genes were not affected by water table management, but the abundance of the nosZ gene did increase from April to September, while amoA gene abundance decreased.