Nitrous Oxide Emissions in Turfgrass: Effects of Irrigation Amounts and Nitrogen Fertilizer Types.

Nitrous oxide (N₂O) is important greenhouse gases that has been implicated in global climate change and 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. 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. A field study under a automated rainout shelter was conducted in Manhattan, KS from October 2014 to November 2016 on ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) maintained at 2.54 cm height. Two irrigation levels were implemented, a medium (66% evapotranspiration [ET_o] replacement) and a medium-low (33% ET_o replacement). The N-fertilization treatments included urea, slow-release (polymer-coated N), and an untreated no-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. Visual turf quality and green cover percentage calculated by digital images were measured during the summer. In the first year of measurements, urea fertilizer had higher peak N₂O-N fluxes (ug N m^-2/h^-1) after fertilization and overall annual emissions than polymer-coated N-fertilizer and differences were negligible due to irrigation treatment. Responses of N₂O fluxes to N fertilization and irrigation treatments, and cumulative N₂O fluxes during the entire 2-yr study period will be reported.