Kristina S. Walker, 205 Hill Hall, University of Minnesota, Crookston, MN and Katy E.. Smith, Department of Math, Science, and Technol, University of Minnesota Crookston, Crookston, MN
Soil moisture and temperature are known predictors of greenhouse gas (GHG) losses from highly managed turfgrass. Irrigation management practices that conserve water use have the potential to reduce GHG losses but may adversely affect overall turfgrass quality. A field study was developed to evaluate the impact irrigation regimes (Business as Usual, Supplemental Rainfall, Syringing, and Natural Rainfall), nitrogen (N) source (Urea and Milorganite), and rate (146 kg N ha-1 yr-1 and 293 kg N ha-1 yr-1) has on GHG (carbon dioxide [CO2], methane [CH4], and nitrous oxide [N2O]) emissions from creeping bentgrass (Agrostis stolonifera) greens. Sampling occurred weekly throughout the 2015-2106 growing season. Gas samples were taken using a vented closed gas chamber for 40 minutes following USDA-ARS GRACEnet methods. Soil temperature, soil moisture, canopy temperature, canopy greenness, and turfgrass quality data were also collected. Results indicate that nitrogen sources applied at the high N rate resulted in significantly higher (p<0.01) emissions of both CO2 and N2O. Irrigation practices exposed to full sunlight (Supplemental Rainfall & Syringing), thus having a higher soil temperature, resulted in significantly higher emissions of both CO2 and N2O; the reverse was true for irrigation treatments experiencing shade from nearby trees (Business as Usual, Natural Rainfall). Both turfgrass quality and canopy greenness were significantly (p<0.05) impacted by irrigation practices, N source, and rate. Canopy greenness was improved with the higher rate of Milorganite and Urea. Higher turfgrass quality was associated with the use of Milorganite at both the high and low N rates. Canopy temperature was significantly (p<0.001) affected my irrigation regime; supplemental rainfall and syringing had elevated canopy temperatures due to a lack of shade and moisture. Water conservation practices implemented on non-shaded greens resulted in higher soil and canopy temperatures that contributed to GHG losses from creeping bentgrass putting greens.