Measurements of nitrous oxide (N₂O) emissions were made using mini-chambers placed at 100 locations over an 8,100 m² area of irrigated dairy pasture to characterize the spatial variability in emissions and to improve understanding of its causes. Nitrous oxide fluxes were analysed using geostatistics to discern spatial patterns and to investigate the effects of soil variables on N₂O emissions. Soil variables measured at each location were moisture content, temperature, pH, mineral N, total N and C because these affect microbial activity responsible for N₂O emissions. Experiments were conducted in the summer and autumn of 2004, after grazing events that were followed by urea application and irrigation.

Average N₂O fluxes from the mini-chambers were 160 and 143 ngN-N₂O m^-2 s^-1 for the two experiments and N₂O fluxes showed spatial autocorrelation below 77 and 74 m, respectively. Fluxes were strongly correlated with soil nitrate (NO₃^-1) in the autumn experiment, however compromised soil extractions prevented relationship of fluxes to soil chemical variables being inferred in the summer experiment. The observed N₂O fluxes agreed well with predictions of the submodel of the spatially referenced water and nitrogen (N) management model (WNMM). The average mini-chamber fluxes were compared with fluxes measured by automatic chambers installed at the site as well as by micrometeorological techniques. Average fluxes from the mini-chambers compared well with those of the large chambers, however micrometeorological and mini-chamber results were not in agreement, probably because chambers and atmospheric measurements sampled differing areas.