Variable-rate application of fertiliser – a new tool for farm system and environmental performance?

Nitrogenous fertilisers – especially urea – are key inputs into many farming systems. With increasing restrictions on nitrogen fertiliser application, there is an urgent need to ensure that nitrogen is used effectively. One technology that has been developed to contribute to this challenge is variable-rate application (VRA) of fertiliser. The theory is that fertiliser is applied at higher rates where there is sufficient grass cover to utilise the fertiliser, and at lower rates where grass cover is reduced (or absent). This trial looked at the effect of VRA on pasture production on five farms over one season and estimated the impact of those changes on farm system metrics, including environmental performance. Averaged over all five farms, there was no statistically significant difference between VRA and blanket-rate application of fertiliser on pasture production. However, one farm did show a significant difference. Although the absolute difference was small, it suggested that VRA could be a useful tool in addressing the challenge of driving better farm performance with reduced environmental impact.