Monday, November 13, 2006 - 9:00 AM

Effects of Turfgrass Species on Nitrous Oxide Fluxes under Typical Nitrogen Management Regimes.

Jason Lewis and Dale Bremer. Kansas State University, Throckmorton Plant Sciences Center, Manhattan, KS 66506-5506

Urban ecosystems are rapidly expanding and their effects on atmospheric nitrous oxide (N2O) inventories are unknown.  A field study was initiated to quantify the magnitude and patterns of N2O fluxes and to estimate cumulative seasonal fluxes from three turfgrass species. Soil fluxes of N2O were measured over the summer and fall of 2005 using static surface chambers and gas chromatography. Field plots were established on existing swards of two warm season turfgrasses, bermudagrass (Cynodon dactylon (L.)) and zoysiagrass (Zosia japonica (Steud.)), and one cool season turfgrass, perennial ryegrass (Lolium perenne (L.)) in northeastern Kansas, USA. Plots were fertilized with urea N at 145 kg ha-1 yr-1 in bermudagrass and perennial ryegrass, and 60 kg ha-1 yr-1 in zoysiagrass, which were considered optimum fertilization rates for maintaining high quality turfgrass in each respective species.  Soil temperature and volumetric water content was collected at 5 cm.  Fluxes ranged from 18.9 to 1939.5 µg m-1 hr-1 in bermudagrass, from -11.4 to 767.8 µg m-1 hr-1 in perennial ryegrass, and from 22.3 to 767.8 µg m-1 hr-1 in zoysiagrass.  Seasonal fluxes of N2O during the study were 1.10 kg ha-1 in bermudagrass, 0.57 kg ha-1 in perennial ryegrass, and 0.82 kg ha-1 in zoysiagrass. Fluxes from perennial ryegrass were lower than from bermudagrass, despite receiving the same N nutrition input.  Fluxes of N2O were generally greater when soil water content increased.  Results indicated significant N2O emissions from the three turfgrass species that were strongly affected by management practices, which potentially could be manipulated to reduce N2O emissions from urban landscapes.