Nitrous Oxide (N₂O) is a potent greenhouse gas, with limited information concerning emissions from intensive dairy pastures in Australia. The objective of this research is to attempt to distinguish the contribution of nitrification and denitrification to N₂O emissions from intensive dairy pasture systems over a range of soil types. The soil environmental factors under investigation include the effect of water filled pore space (WFPS), available substrate levels and temperature; with results used calibrate the N₂O components of DairyMod and the Water and Nitrogen Management Model (WNMM). This will enhance the prediction of N₂O emissions, facilitating the development and testing of best management practices. The techniques applied to quantify denitrification and N₂/N₂O ratios from denitrification in incubation studies were acetylene (C₂H₂) inhibition, nitrate balance and two ¹⁵N labelling techniques, (mass balance of ¹⁵N-nitrate and the direct determination of ¹⁵N-(N₂O + N₂) in head space gases).

Preliminary results indicate that C₂H₂ is not 100% effective in inhibiting the reduction of N₂O to N₂, resulting in the use of ¹⁵N tracer techniques to distinguish the contribution of nitrification and denitrification to N₂O emission.