Nitrous oxide (N₂O) is a greenhouse gas, with a global warming potential 300 times that of carbon dioxide (CO₂). Agriculture is responsible for 25-35% of Australia’s greenhouse gas emissions and the Australian Greenhouse Office estimates that N₂O contributes ~17.5% of agricultural emissions. There is large uncertainty in these estimates because there are few measurements from Australia and emission rates vary in space and time. N₂O emissions are thus poorly quantified and there is insufficient information for development of management options to reduce these emissions.

N₂O is produced primarily through denitrification, and to a lesser extent during nitrification. N₂O emissions are dependent on many factors, but especially on soil moisture content, labile soil carbon (C) supply and substrate availability. Large emissions typically occur after rain or irrigation events in systems with high nitrogen (N) and C availability, and are attributed to denitrification occurring under anaerobic conditions in wet soil.

To characterise the spatial variability and further understand the mechanisms contributing to emissions, 100 mini chambers were placed over a 100 m ² area of irrigated dairy pasture at the Kyabram Dairy Centre, DPI Victoria, and the head space was sampled for N₂O. Soil properties (soil moisture, pH, mineral N, total N and C) under each chamber were be measured, and N₂O fluxes analysed geostatistically to discern spatial patterns. The experiment was conducted twice, soon after two separate events of urea application with follow-up irrigation. Average N₂O fluxes from the chambers will be compared with fluxes calculated by micrometeorological techniques at the site.