Ecosystem-scale measurements of nitrous oxide fluxes for an intensely grazed, fertilized grassland

An eddy covariance (EC) system with a tunable diode laser trace gas analyzer was used in a field setting in Ireland to measure N2O emissions on a continuous basis over an eight-month period, spanning a range of seasonal conditions. Intensely-grazed grassland fields within the footprint area of the EC sensors were subject to chemical fertilizer and slurry applications in order to boost grassland yield, and the amounts of these applications were documented by the farmers on a monthly basis. Three major emission events, covering a timeframe of 16 days (6.6% of the measurement period) contributed to over half (51.1%) of the observed cumulative flux. Two of these events occurred during the summer, while the third occurred during the winter, with vastly different soil moisture and soil temperature conditions associated with these times of the year. The type of N applications (fertilizer vs. slurry), soil moisture and temperature status had implications for controlling the short-term rates of N2O emissions. Cumulative N2O emissions, however, were driven by fertilizer and slurry N applications, as the emission factor of approximately 3.0% displayed consistency throughout the eight-month period.