Nitrous Oxide Emissions and Carbon Sequestration in Turfgrass: Effects of Irrigation and N Fertilization.

Nitrous oxide (N₂O) and carbon dioxide (CO₂) are important greenhouse gases that have been implicated in global climate change. Furthermore, N₂O is the most important ozone-depleting substance in the atmosphere. Turfgrass systems are typically fertilized with nitrogen (N) and irrigated, which may result in significant N₂O emissions. Turfgrass also has the capacity to sequester or emit CO₂ from/into the atmosphere via photosynthesis and respiration. The development of management practices such as slow-release N fertilizer and/or deficit irrigation may mitigate N₂O emissions, but also affect carbon sequestration in turf soils. Our objective was to quantify the magnitude and patterns of N₂O emissions in turfgrass and determine how irrigation and N fertilization may be managed to reduce N₂O emissions and enhance carbon sequestration. A field study under a automated rainout shelter was conducted in Manhattan, KS from October 2014 to November 2015 on ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) maintained at 2.54 cm height. Two irrigation levels were implemented, a medium (75% evapotranspiration [ET] replacement) and a medium-low (50% ET replacement). The N-fertilization treatments included urea and a polymer-coated N, total application was 97.6 kg N ha^-1. N₂O emissions were measured periodically by static chambers placed over the turf surface and gas chromatography. Anicillary measurements of soil moisture, temperature, and ammonium and nitrate were collected at each sampling event. There were minimal differences in N₂O-N fluxes (ug N m^-2/h^-1) from October through May. Responses of N₂O fluxes to N fertilization and irrigation during the summer and fall periods, and cumulative N₂O fluxes during the entire study period will be reported.