New trials on Mackay farms are testing ways to trap pesticide waste at the source – and early results show they can stop contamination at hotspots like chemical mixing and wash-down sites.

Farmacist, an agricultural advisory service based in the region, are the first in Australia to develop and implement ‘biobeds’. These recyclable on-farm systems create an environment rich in microorganisms, naturally breaking down 99% of pesticides in contaminated water to levels where they are no longer harmful.

Growers can create biobeds using materials mostly already on the farm, like soil, cane trash, compost and mill mud in 1000L intermediate bulk containers (commonly used on farms for storing liquids).  

It is low-cost, simple to set up and shows strong potential to reduce harmful pesticide exposure to both people and the environment in the long-term.

Pesticide hotspots overlooked

Until recently, chemical mixing and wash-down were not recognised as an important source of contamination. But recent monitoring has revealed how significant they can be.

Sugarcane grower and Farmacist director Rob Sluggett, said mixing and wash-down sites are likely hotspots because chemicals are mixed at the same site year after year. 

“Each time a we rinse  out spray equipment, flush the boom, or we have a spill, pesticide residues build up at that site,” he said.

“You can often see the effects at these sites. There’s little to no grass or vegetation growing, sometimes discoloured soil, and even a chemical smell.”

While these sites may seem small and contained, runoff sampling shows they can contribute significantly to pesticide contamination if not properly managed, risking movement into groundwater and runoff into waterways.

“Raising awareness is the first step. When growers see their results, from their own sampling, they want to act. At first though, we didn’t have a clear solution to the problem and then my team trialled biobeds,” he said.

“Early trials show Biobeds can bring pesticide levels down to safer limits in a practical way on the farm. There’s still work to do to fine-tune the design, but the system is already showing real promise.”

What the data says in the Mackay region

Pesticides are essential for protecting crops from pests like sugarcane grubs and invasive weeds – without them, farmers risk having crops with lower yield, reducing the profitability of the farm. Yet, water quality monitoring programs have detected pesticides in local waterways, with the Mackay Whitsunday region recording some of the highest concentrations in the Great Barrier Reef catchment.

Water quality scientist, Associate Professor Ryan Turner, and University of Queensland’s Director of the Reef Catchments Science Partnership, works with growers across the Great Barrier Reef to reduce pesticides and fertiliser losses.

“Extensive monitoring has shown that certain pesticides are regularly detected in some freshwater waterways in the greater Mackay region. At times, the levels exceed what’s considered safe for ecosystems. We’ve also found that the commonly detected pesticides are often the most harmful to the environment,” he said.

“The challenge is managing pesticide losses from the landscape and recognising that these losses travel through a complex network of waterways, wetlands, and groundwater systems.

“That’s why we need initiatives like biobeds. It targets high risk areas and results from trials indicate there is potential for it to significantly help bring pesticide concentrations down in waterways.”

The region boasts a strong history of rigorous water quality monitoring across paddock and creek scales. Many growers in the region are adopting improved farm management practices and are involved in various Reef programs.

“This kind of close partnership drives real progress. It bridges the gap between science and agriculture to support growers and extension staff in managing pesticides more effectively,” said Associate Professor Turner.

Scaling biobeds across catchments

Dr Zoe Bainbridge, TropWATER water quality scientist and facilitator of the Water Quality Science and Agriculture Hub, said these kinds of initiatives need to be more accessible to growers.

“Here we have farmers, extension staff, and scientists working together to find solutions that are low-cost and realistic for farmers to implement,” she said.

“This was a trial, but a very successful one. Now it’s about scaling it up and making this science more accessible to other growers in this region and across the Great Barrier Reef catchment.

“This is exactly what the Water Quality Science and Agriculture Hub is about. We’re helping connect extension staff and growers with rigorous, relevant water quality science and initiatives – giving farmers the confidence to adopt practices that reduce off-farm losses while maintaining profitability.”

This project was funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation, under the Regional Water Quality Program. Additional funding was provided by Farmacist Pty Ltd.