Carbon and Sustainability – A demonstration on vegetable properties across Australia
Five demonstration sites were established on four vegetable production farms on the east coast of Australia. These sites were used to trial and implement greenhouse gas (GHG) emission reduction techniques to increase the ability of the vegetable industry to manage their emissions and improve their productivity. On farm demonstration and communication of the business case were used as drivers for the uptake of these practices to reduce GHG emissions. The project also aimed to provide information for vegetable producers to supply produce that meets consumers growing demand for food that is grown in sustainable and low emissions production systems. Farm demonstrations focussed primarily on reducing GHG emissions from the application of fertilisers. While potential exists to reduce GHG emissions from energy use and fuel use on farm, the most immediate opportunity to reduce emissions without significant capital investment, or changing any other practices, came from changed fertiliser practices. This project has clearly demonstrated that nitrification inhibitors can very effectively reduce nitrous oxide (N2O) emissions in vegetable crop production. Further research is required however to understand which type of inhibitor fits best with what crop. In these trials the potential of a nitrification inhibitor to reduce GHG emissions (N2O emissions) was heavily dependent on the type of inhibitor/fertiliser combination, and whether organic amendments were also added to the production system. The effect of inhibitors on GHG emissions could not be considered alone within this demonstration study. Trials have also shown another major benefit of nitrification inhibitors i.e. improved nitrogen (N) use efficiency. This has the potential to reduce nitrate leaching, reducing pollution of groundwater and offer great potential to reduce the number of applications of high analysis fertilisers, particularly calcium nitrate (CaNO3), treatments to vegetable crops without reductions in yield. The results in trials in Victoria in 2012 indicated that at least one fertiliser application could be dropped due to improved N efficiency. This saves fertiliser costs, fuel costs and labour costs estimated at over $500/ha. It indirectly also allows reduced fertiliser application rates for crop production which will further lower N2O emissions. Therefore a key finding from this research is the need to understand the effect of inhibitors on the total nitrogen budget of the vegetable production system. Manures were found to emit GHG’s at rates of up to 20 times higher than inorganic fertilisers in this project. Given this result and the frequent use of manures in vegetable production systems, there is great potential to reduce GHG emissions through better manure management. Trials conducted in Victoria demonstrated a 19% reduction in GHG emissions from the application of nitrification inhibitors on manure on the surface, and a 60% reduction on manure treated with inhibitors and incorporated into the soil. This result is significant and practice change as a result of this work can be immediate. The added benefit of inhibitors on manure was the increased yield response seen across the trials (in the absence of the CaNO3 side dressing). This project has identified areas for improved emissions management on vegetable farms. However, the demonstration focus in the two year period has only just scratched the surface in terms of answering some of the complex questions related to reducing GHG emissions on farm. Further work is needed to understand the complexity of emissions reduction across such a diverse industry and the integrated supply chain. This being said, this project has provided the vegetable industry with enough information to make more informed management decisions on farm to reduce GHG emissions.