Progress towards variable rate N application within block – understanding crop N response

Nitrogen (N) fertiliser inputs for the majority of the Australian sugarcane industry are regulated in order to minimise off-site environmental impacts. There is on-going pressure to improve N use efficiency from an environmental but also economic perspective. Variable rate N application within block is uncommon in the sugarcane industry but may allow further refinement and advancement of the industry’s nutrient management practices. A key to implementing a variable rate N management program within block is to better understand crop responsiveness to N inputs and how this varies spatially. Simple solutions like applying more N on high yielding zones and less N on low yielding zones may not always be the most appropriate approach. The project will use N rate strips (low, standard, high) that run through variable soil conditions within block in order to better understand crop responsiveness. A combination of remote sensing, crop sampling, in-depth soil characterisation and machine learning tools will be used to explore key drivers of N response. Ultimately the projects aims to increase understanding of crop response to N across variable block conditions so that a robust approach for implementing variable rate N application can be introduced to industry.

The project aims to improve nitrogen use efficiency by developing a robust method to implement variable rate N management within block. To do this it will:
• Quantify changes in crop N responsiveness within blocks that have underlying soil/site variability.
• Characterise changes in soil traits across these variable blocks in order to interpret crop N response.
• Utilise remote sensing tools to assess crop biomass development, responsiveness to N and N uptake.
• Analyse data using a machine learning approach to explore relationship between soil traits and crop N response.
• Determine potential methodology to implement variable rate N management in sugarcane farming systems.