Nitrous oxide (N₂O) emissions from broadacre cropping represent both the emission of a potent greenhouse gas (GWP 298, IPCC 2007) and the loss of an important nutrient. DEPI in collaboration with the Wimmera Catchment Management Authority, BCG and the Irrigated Cropping Council have commenced a program comprising replicated research trials, ‘in paddock’ demonstrations and communication of options for mitigating these emissions as part of the ‘Carbon Farming Futures’ program. Preliminary findings indicate that generally N₂O emissions are low, particularly from a productivity perspective (<10 g N₂O-N/ha/day). This paper presents preliminary findings and experiences from an integrated program, focusing on identifying and communicating mitigation options where productivity impacts can be marginal.

Six field sites were established during 2012 across high, medium and low rainfall zones plus two sites under irrigation in Victoria to investigate the impact of various options for mitigation of N₂O loss. Mitigation options included altered fertiliser rates and timing as well as applying nitrification and urease inhibitors; other sites focussed on decision support tools to guide fertiliser management strategies. Emissions were measured using static chambers with the most intensive measurements undertaken at the ‘research’ sites (Horsham and Hamilton). Measurements at other sites were less intensive but targeted towards periods when anticipated emissions were likely to be greatest (following fertiliser application and rainfall or irrigation events). Introductory communications activities were also undertaken with collaborating grower groups during the first season.

Nitrous oxide emissions were low at most sites (except high rainfall and irrigation situations),  peaking at  <10 g N₂O-N/ha/day in farming systems where  up to 50 kg/ha of fertiliser N is often applied annually.  However grain yield responses were often significant, providing a critical financial impact for farmers. Early indications suggest that separating inherent ‘background’ emissions from management induced increases can be difficult in line with Harris et al 2013.  As a result, communications activities undertaken have focussed on two main areas: (i) developing understanding of key drivers behind N₂O loss so that participants can take a risk based view of their farming system, (ii) tools and strategies to better match nitrogen supply to crop demand thereby enhancing productivity/profitability (with  reduced risk of excess N₂O loss an added bonus).  It is suggested that in  environments where the productivity cost of N₂O loss is low and there is no cost placed on these emissions that a risk mitigation approach such as this is adopted.