Rui Liu1, Helen Suter1, Helen L Hayden2, Jizheng He1, Deli Chen1
1 Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia
2 Department of Economic Development, Jobs, Transport and Resources, Bundoora, Victoria 3083, Australia
The continuous increase of the greenhouse gas nitrous oxide (N2O) in the atmosphere due to increasing anthropogenic nitrogen input in agriculture has become a global concern. In recent years, identification of the microbial sources responsible for soil N2O production has substantially advanced with the development of isotope enrichment techniques and the discovery of specific nitrogen-cycling functional genes. However, little information is available to effectively quantify the N2O produced from different microbial pathways (i.e. nitrification and denitrification). 15N-tracing incubation experiments were conducted, using soil from different land-uses, under controlled laboratory conditions to quantify nitrification-sourced N2O production. Nitrification was found to be the main contributor to N2O production, contributing to 96.7% of the N2O emissions in the sugarcane soil followed by 70.9% in the cereal cropping soil and 70.9% in the dairy pasture soil, while only around 20.0% of N2O was produced from nitrification in vegetable soil. The greatest contribution from nitrification was observed at 50% and 70% WFPS regardless of soil temperature. At 50%, 70% and 85% WFPS, nitrification contributed 87%, 80% and 53% of total N2O production, respectively at 25°C, and 86%, 74% and 33% of total N2O production, respectively at 35°C. These findings can be used to develop better models for simulating N2O from nitrification to inform soil management practices for improved N use efficiency.