The Effects of Fertilizer Sources on the Mitigation of Greenhouse Gas Emissions from Creeping Bentgrass Greens and Kentucky Bluegrass Roughs.

The purpose of this project is to determine the impact that cultural management strategies have on greenhouse gas emissions which are known to contribute to global climate change. An ongoing field study evaluating fertilizer source (Urea, Encapsulated Polyon, and Milorganite), turfgrass species (Agrostis stolonifera and Poa pratensis), and site location (soil moisture regime) on greenhouse gas (carbon dioxide [CO₂], methane [CH₄], and nitrous oxide [N₂O]) emissions was initiated in June 2013. Samplings occurred weekly throughout the summer and fall of 2013 and will continue through 2014. Gas samples were taken using a vented closed gas chamber that was placed over the plots for 40 minutes following the USDA-ARS GRACEnet methods. Soil temperature, soil moisture, canopy greenness, and turfgrass quality were also collected. Results from 2013 show a trend (p<0.1) indicating higher CO₂ emissions on the green than on the two rough sites. Methane (CH₄) emissions were significantly (p<0.05) higher in the control than in the encapsulated polyon treatment across all sites. Site location also showed significant (p<0.001) influence on N₂O emissions; although treatment effects were not significant.  The rough in the dry location showed significantly higher N₂O emissions than the other two sites; this trend was consistent across sampling dates. Soil temperature and soil moisture were found to be significant predictors of CO₂ and N₂O emissions. Site location was significant (p<.0001) for canopy greenness on all sampling dates in 2013 except for two dates in September following fertilization. Fertilizer source was significant on four of the sampling dates where turfgrass quality was significantly (p<.0001) higher for the Milorganite and Urea treatments compared to the control. The results from this study will provide information about turfgrass management practices that minimize greenhouse gas losses for cool-season turfgrasses which can be utilized to evaluate the environmental efficacy of our current cultural management practices.