THE ASSESSMENT OF ENHANCED EFFICIENCY FERTILISERS (EEFs) IN A GLASSHOUSE EXPERIMENT TO INVESTIGATE NITROGEN LOSS PATHWAYS IN SUGARCANE

NITROGEN (N) LOSS RESULTING in negative offsite environmental impacts is an important issue for the sugarcane industry in tropical Australia. Enhanced Efficiency Fertilisers (EEFs) have the potential to reduce nutrient losses leading to improvements in nutrient uptake efficiency, productivity gains and environmental impacts. A glasshouse experiment compared fertiliser N lost in drainage and as nitrous oxide for conventional urea, polymer coated urea (PCU – AgroMaster®) and urea treated with DMPP (Entec®) applied at a rate equivalent to 100 kg N/ha. Loss of N in leachate at day 50 for PCU was approximately half that of urea and DMPP, which were similar (~28 mg/pot). Most of the N was leached as NOx–N (>77%) at both day 50 and day 150, when losses were low and similar for all treatments (<2.4 mg/pot). Both EEFs were effective in reducing loss of N as N2O at 50 days after fertiliser application. Nitrogen loss for DMPP was only 18% of the loss of N from urea, while PCU loss was 62% of that of urea. However, the maximum daily loss of N as N2O of 0.04 mg/pot/day at day 50 was very low in comparison to that lost in leachate (~28 mg/pot) at the same time. These results provide options for the selection of EEF based on anticipated loss pathway for a combination of soil type, position in landscape, and seasonal weather outlook. PCU, or a blend with urea, is the preferred N fertiliser for well-drained sites in higher rainfall areas where rate of leaching is expected to be high. DMPP, or a blend with urea, would be the preferred N fertiliser for poorly drained sites in wet areas or for prolonged wet growing conditions, where rate of N2O emission is expected to be high.