Can improved fertiliser technology allow reduced fertiliser N rates in sugarcane?

Mike Bell

The dominant form of nitrogen (N) lost from the sugarcane industry via surface runoff and deep drainage is dissolved inorganic N (DIN) derived from fertiliser applications. This N form represents an immediate risk to marine ecosystem health. Minimising DIN losses requires a combination of management strategies that collectively maximise the proportion of fertiliser N captured by the crop while minimising the risk of DIN loss in runoff or deep drainage. The large sugarcane N requirement, coupled with an extended period of crop N uptake that can coincide with the monsoonal wet-season, makes these objectives challenging.

Our NESP project explored the feasibility of combining new fertiliser technologies (Enhanced Efficiency Fertilisers – EEF’s) with N application rates matched to historical records of productivity at the block scale as a way of maintaining productivity while improving fertiliser N recovery and minimising N loss. This work, at seven sites and focussed on high-risk times of fertiliser N application, was complimented by a much larger scale program (EEF60) funded by Reef Trust IV. This investment used a similar approach, although with a constant proportional N rate reduction of 20%, establishing 60 sites on different soil types and fertiliser application times across Reef catchments.

Our results show that using EEF’s can reduce the risk of yield loss from reduced N rates, and reduce runoff losses in most instances, provided the crop is able to acquire the N as it is released. The higher cost of EEF products/kg N applied will be a driver for product choice in the industry.