A newly developed pesticide risk assessment method could determine whether climate change will increase or decrease the risk of pesticides leaching through the soil profile and contaminating ground water and the environment.
Rainstorms could be washing pesticides out the farm gate and across the countryside, contaminating water bodies in their wake.
This is a concern, considering that about 31,000 tonnes of insecticides, herbicides and fungicides are applied annually across Australia.
The University of Western Australia (UWA) Faculty of Natural and Agricultural Sciences has therefore developed a risk assessment method, combining three key factors: rainfall characteristics; soil properties controlling water flow; and pesticide fate in soil.
UWA School of Earth and Geographical Sciences senior lecturer, Dr Christoph Hinz said the common myth that once pesticides had served their purpose they degraded into harmless substances, before reaching groundwater, was a fallacy.
“Unfortunately, pesticide residues can be found in almost all water bodies, from groundwater to streams and lakes, indicating they might move more rapidly and further than expected,” he said.
Previous pesticide risk assessments ignored the importance of rainfall and climate, which can cause fast flow events.
The new assessment method developed by Dr Hinz and his PhD student, Gavan McGrath, was funded by the Water Corporation and the Australian Research Council.
Dr Hinz explained that the first step was to assess if a rainfall event would cause a fast flow event that carried pesticides off-site.
“However, to unravel this we need to understand how rainfall occurs and look at rainfall at time intervals as regular as minutes, which represent a much higher temporal resolution than reported by the Bureau of Meteorology.
“We also need to know the intensity that fast flow processes are triggered, which requires us to have in-depth understanding of soil properties,” he said.
“Thirdly, we need to assess how much pesticide will be released from the soil to be transported with the fast flowing water, which related to how pesticides are retained by the soil and how quickly they degrade,” Dr Hinz said.
“Combining the three factors allowed improved assessment of the risk of which storm, of all storms occurring annually, would generate fast flow events carrying pesticides offsite.
“The more frequent these critical events are, the greater the risk.
“Using new models that capture rainfall’s characteristics, from minute to daily resolution, we can now develop risk maps for specific environments and soil types,” he said.
According to UWA Institute of Agriculture Director, Professor Kadambot Siddique, this demonstrated UWA’s capacity for solutions oriented research which incorporated fundamental and applied science.
“With Australian growers spending an average of $40,000 a year on crop and pasture chemicals, any savings from better climate forecasting, decision support systems and risk assessment would improve productivity and benefit the environment,” he said.
Professor Kadambot Siddique, Telephone (+61 8) 6488 7012, Mobile 0411 155 396
Dr Christoph Hinz, Telephone (+61 8) 6488 3466