Nutrients and pesticides in end-of-paddock run-off water for farming practices in the Central region

Results from end-of-paddock run-off water quality monitoring conducted in the Central region are presented. By measuring nutrient and pesticide concentrations in run-off leaving the paddocks, we aimed to identify farming practices with reduced environmental footprints. This knowledge can be used by growers and advisors to select farming practices that are less harmful for the environment, specifically local waterways and the Great Barrier Reef lagoon. Three trial sites were implemented in the 2022/2023 growing season. Each trial was designed as a strip trial, with treatments replicated two or three times. At each site, nutrient and pesticide concentrations in run-off were monitored over the wet season. Side dress application of liquid imidacloprid in ratoons appeared to reduce imidacloprid load leaving the paddock as compared to stool split application. Liquid imidacloprid and granular slow release imidacloprid applied at fill-in stage of a plant cane crop showed similar imidacloprid losses in run-off water leaving the paddock. DIN run-off losses for an Enhanced Efficiency Fertiliser (EEF) compared to a sub-surface applied liquid fertiliser were lower at the first run-off event, but higher at subsequent run-off events. Banded mill mud increased the run-off of isoxaflutole and amicarbazone compared to where no mill mud had been applied, where the herbicides had been applied above the banded mill mud. Placing the herbicides beneath the banded mill mud appeared to further increase the run-off losses of the two residual herbicides.