Researchers reduce herbicide run-off in sugar cane crops
Scientists from CSIRO’s Water for a Healthy Country Flagship have trialled a new approach to sugar cane plantation weed management in select Great Barrier Reef (GBR) catchments. The results of their study have been published in the journal Science of the Total Environment.
CSIRO research leader Dr Rai Kookana explained, “The conventional application of herbicides in furrow-irrigated sugar cane production is to broadcast spray across the whole field using boom sprayers, which applies herbicides to both beds and furrows. Irrigation water then carries the herbicides with the tail water into the drainage channels, into nearby creeks and rivers and potentially into the GBR lagoon.”
PSII herbicides are known to negatively impact reef ecosystems. According to Jon Brodie of James Cook University, “the amount of some herbicides in creek and estuarine waters during [the dry season] regularly exceeds Australian water quality guidelines and could potentially affect, for example, coastal seagrass”.
The new technique involves the use of a specially adapted shielded sprayer to apply the herbicides to only raised beds of furrow-irrigated sugar cane. It has been found to dramatically minimise the likelihood of PSII herbicides such as diuron, atrazine, ametryn and hexazinone coming into contact with irrigation water, resulting in a 90% reduction of herbicide run-off into waterways despite only covering 60% less area.
CSIRO scientist Danni Oliver said, “while there will certainly be some herbicide loss following the first irrigation or rainfall event, the marked decreases in losses documented in this study … could lead to significant improvements in off-site water quality, particularly during the dry season.”
Dr Kookana said the results “clearly demonstrate that the use of precision herbicide application technologies by the industry, including using shielded sprayers for furrow-irrigated sugar cane cultivation, can be highly effective in reducing herbicide run-off”. He suggests additional testing across different soil types and farming systems, and possibly with different combinations of chemicals.
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