DIFFERENT NITROGEN MANAGEMENT REGIMES AFFECT NITROUS OXIDE EMISSIONS AMONG ONE COOL-SEASON AND TWO WARM-SEASON TURFGRASSES

摘要

Emissions of nitrous oxide (N2O) from turfgrass may be increasing with urban expansion,but varying N management regimes among species may affect N2O emissions and turfgrass selection may be a means to mitigate N2O emissions.Our objectives were to quantify N2O fluxes in one coolseason and two warm-season turfgrasses under typical Nmanagement in the temperate,continental climate of Kansas,USA.Turfgrasses investigated were bermudagrass (Cynodon dactylon L.Pers.x C.transvaalensis Burtt-Davy) and perennial ryegrass,(Lolium perenne L.) with N applications of 200 kg N ha-1 yr-1,and zoysiagrass,(Zoysia japonica Steud.) with N applications of 100 kg N ha-1 yr-1.Emissions of N2O were measured weekly for 600 days using static surface chambers and gas chromatography.Fluxes of N2O ranged from 1,633 μg N2O-N m-2 hr-1 after summer fertilization to -17.63 μg N2O-N m-2 hr-1 in late fall.Fluxes of N2O generally increased 4.2 to 9.8 times above prefertilization levels after N application and with increases in soil water content and soil temperature.Flux responses after N applications were greater in summer than fall,especially when accompanied by significant rainfall.Summer fluxes from perennial ryegrass averaged 26% lower than bermudagrass and zoysiagrass,but fluxes in fall were highest in perennial ryegrass among species,following patterns of N fertilization timing.Cumulative annual N2O-N emissions were 3.36,3.35,3.12 kg N ha-1 yr-1 for bermudagrass,perennial ryegrass,and zoysiagrass,respectively,but differences were not significant among species.Data did not support our hypothesis that species selection can be used for mitigating N2O emissions from turfgrass,although further research may be warranted.