99% efficient bioreactors, but whole-farm action matters
Horticultural producers on the North Coast are being encouraged to strengthen on-farm nutrient management, with innovative woodchip bioreactors proving their effectiveness in significantly reducing fertiliser pollution entering local waterways.
As part of an ongoing partnership between North Coast Local Land Services and City of Coffs Harbour, recent field trials conducted by Southern Cross University have shown the latest bioreactor designs can reduce nitrate (fertiliser) runoff into nearby waterways by up to 99%. The bioreactors use woodchips to support naturally occurring bacteria that convert excess nitrate in farm drainage into harmless nitrogen gas before water leaves the property.
The technology has proven particularly effective in high-intensity horticultural systems residing near important environmental assets such as the Solitary Islands Marine Park where nutrient-rich runoff poses a significant risk to biodiversity and water quality.
Senior Land Services Officer, Shaun Morris, said the results confirm bioreactors are an important tool and work best when supported by effective input management across the farm.
“Our research shows bioreactors can help treat a range of farm effluents including nitrate, phosphate and pesticides before they leave the property.”
Excess nitrate runoff not only degrades water quality and aquatic ecosystems, it can also release nitrous oxide to the atmosphere - a greenhouse gas with a global warming potential around 300 times greater than carbon dioxide.
North Coast Local Land Services General Manager, Alison Bowman, said climate change and water quality pressures mean horticultural producers need practical, cost-effective solutions that maintain productivity while protecting the environment.
“Climate variability, intense rainfall events and rising environmental risks are already affecting farming on the North Coast,” Alison said.
“Bioreactors are a valuable mitigation tool, but long-term protection of waterways relies on improving how nutrients, water and chemicals are managed across the farm.”
Research by Southern Cross University has shown that drainage water from some intensive systems can contain nitrate levels many thousands of times higher than water quality guidelines, particularly where fertiliser and irrigation are not well matched to crop demand.
“These results were made possible as a result of detailed research by PhD student Rebecca Woodrow who was able to show the effectiveness of bioreactors using specialised equipment,” said Professor Christian Sanders from the Southern Cross University, National Marine Science Centre.
North Coast LLS works with horticultural producers to reduce these risks through practical, tailored advice. Optimising fertiliser use is one of the most effective steps growers can take. Regular soil and tissue testing helps match fertiliser rates to crop needs, reducing excess application and saving input costs. Split fertiliser applications timed to crop growth can further improve nutrient uptake and reduce losses.
Shaun continued, saying improving irrigation management is the first step needed in reducing excessive fertiliser runoff laying the platform for improved production and reduced inputs.
“Efficient irrigation plays an equally critical role in nutrient management. Drip irrigation systems, accurate scheduling, and monitoring soil moisture can significantly reduce fertiliser loss while maintaining crop performance.”
Pesticide management is another key area. Integrated pest management approaches, combined with precision application, can reduce chemical use while maintaining crop protection. Vegetated buffer strips and grassed drains can also help reduce nutrients and chemicals before they reach waterways.
Ongoing efforts by North Coast LLS include pairing improved irrigation practices with refined bioreactor designs, and testing these efficiencies under extreme weather conditions, promoting their future uptake across the region.
“Real progress comes when growers, researchers and industry work together, to see solutions that are practical, effective and scalable,” Shaun continued.
Horticultural producers interested in improving nutrient management or learning more about bioreactors and runoff treatment options are encouraged to contact North Coast Local Land Services on 1300 795 299 for tailored advice and support.
Media Contact: For more information, please contact Michelle Gapes, Regional Communications Advisor, North Coast/Hunter via email michelle.gapes@lls.nsw.gov.au or 0467 291 890