Investigation of the contribution of nitrification and denitrification to nitrous oxide emissions from intensive dairy pastures
1The University of Melbourne, Institute of Land and Food Resources, Parkville, Melbourne, Victoria 3010, Australia. E-mail: ljwylie@pgrad.unimelb.edu.au
2Victorian Department of Primary Industries, Ellinbank, Victoria, 3820, Australia.
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.
