Nitrous oxide emissions from wheat grown in a medium rainfall environment in SE Australia are low compared to overall nitrogen losses

Ashley Wallace1,4,5, Roger Armstrong1,2, Rob Harris3, Oxana Bellyaeva1, Peter Grace4, Clemens Scheer4

1 Department of Economic Development, Jobs, Transport and Resources, Private Bag 260, Horsham, Victoria, 3400.

2 Department of Animal, Plant and Soil Sciences, LaTrobe University, Bundoora, Victoria, 3086.

3 Formerly: Department of Economic Development, Jobs, Transport and Resources, Private Bag 105, Hamilton, Victoria, 3300.

4 Institute for Future Environments, Queensland University of Technology, Brisbane, Qld, 4000.

5 Corresponding author: [email protected]

Abstract

Efficient management of nitrogen (N) is critical to the profitability and sustainability of agricultural systems. Losses of N can both reduce productivity and in the case of  nitrous oxide (N2O) emissions contribute to global warming and ozone depletion. The limited number of studies from medium rainfall cropping systems have indicated that N2O  losses tend to be low to moderate, but that there is the potential to reduce these losses through altered fertiliser management. This study investigated the magnitude of N2O flux from a medium rainfall cropping system in south eastern Australia and the potential to mitigate N2O losses through altered timing (at sowing compared with in-season) of N application and the use of both nitrification and urease inhibitors. This study also measured overall N fertiliser losses and crop productivity. Losses of N2O and overall fertiliser losses were measured using static chamber and 15N mass balance techniques respectively, as part of a field experiment conducted in the Victorian Wimmera during 2012. Cumulative N2O loss from sowing until harvest of the wheat crop amounted to between 75 and 270 g N2O-N/ha with  fertiliser application significantly increasing losses. In contrast, total losses of fertiliser N ranged from 7‑11 kg N/ha (14-22% of applied N), indicating that N2O losses were low in comparison to both crop requirements and overall N losses.