Nitrous oxide emissions from a fertilized grazed grassland in Ireland

A field experiment was undertaken to compare nitrous oxide (N2O) emissions from a grazed pasture receiving three different nitrogen (N) fertilizer application rates (0, 225 and 390 kg ha− 1) and to identify the effects of controlling variables over a 2-year period (2002 and 2003). The N2O-N losses, expressed as a percent of the N applied, in the cooler and wetter 2002 were 0.2–2.0%. In contrast, the percentage loss in the warmer and drier 2003 (3.5–7.2%) were substantially higher. An empirical model was developed to enable simulations and scenario analysis to be undertaken, assuming various climatic scenarios and N fertilizer application regimes. Results suggest that inter-annual variability due to climatic factors increases with the amount of applied fertilizer N and decreases with frequency of application.