An economic evaluation of controlled release and nitrification inhibiting fertilisers in the Burdekin

THE USE OF controlled release and nitrification inhibiting fertilisers may improve the availability and uptake of Nitrogen (N) by sugarcane under certain soil and climatic conditions, while reducing losses via leaching, runoff and denitrification, and increasing nitrogen use efficiency. This paper utilises production and operational data from twelve Burdekin trial sites during the 2014-15 growing season to evaluate the profitability of using these fertilisers. In particular, this paper examines whether these fertilisers can maintain farmer profitability at N application rates lower than a conventional rate based on the Six Easy Steps guidelines. Out of the 12 trial sites, nine tested rates 40 kg N/ha lower and three tested rates 60 kg N/ha lower. Two controlled release blends were investigated in these trials. One treatment had 25% of total N coated with sulphur and polymer, while the other had 50% coated. For the nine sites that tested rates 40 kg N/ha lower than a conventional rate, analyses of variance were completed for each individual trial site but none identified a significant treatment effect. As all sites in each group had identical fertiliser treatments, multi-environment trial analyses were undertaken to improve statistical power. The results identified that the controlled release treatment with a 50% blend was significantly less profitable than all the other treatments except for the controlled release treatment with a 25% blend. In contrast, for the three sites comparing the conventional N rate with rates 60 kg N/ha less, treatment effects were identified at two of the three individual sites. However, the multi-environment trial analysis indicated no significant effect of treatment