NITROGEN FERTILISER MANAGEMENT IN THE AUSTRALIAN SUGAR INDUSTRY: STRATEGIC OPPORTUNITIES FOR IMPROVED EFFICIENCY

For more than a decade, N fertiliser use has been greater (almost double) than that required to produce the actual cane (and sugar) yields obtained in the Australian sugar industry, with deleterious consequences for productivity, sugar quality and environmental impacts in sugarcane growing areas. Over-application of N fertiliser is a rational reaction by growers to uncertainty about the size of the forthcoming crop and the negative impact of inadequate long-term N fertiliser applications on profitability. New fertiliser management strategies have been developed that provide greater sitespecificity, an important consideration for growers. This paper seeks to identify concepts that may be the basis of further improvements in N fertiliser management. While sustained under application of N fertiliser undoubtedly reduces profitability, there is considerable evidence showing that greatly reducing N fertiliser applications for a single crop does not significantly reduce sugarcane production. Consequently, a new philosophy to N fertiliser management can be envisaged that removes the uncertainty driving growers’ decisions to over-apply N. Rather than aiming to fertilise the coming crop, one could aim to replace the amount of N lost from the previous crop, the majority of which is in harvested cane and can be easily estimated. To better examine this new ‘replacement’ N management strategy, long-term simulations were undertaken of a trash management experiment in Mackay. The replacement strategy had similar productivity, greater profitability and lower environmental N losses than conventional N fertiliser management. The ‘replacement’ strategy is evidence based, transparent and defensible; all attributes that are important for the sugar industry to maintain selfregulation of N fertiliser management. We suggest that the N replacement concept in may be useful for further improvements in N fertiliser management.