AN UNUSABLE piece of water-logged land on a Tully banana farm has been transformed into a wetland in a bid to improve run-off water quality.
Tully grower, Patrick Leahy, saw potential for a constructed wetland on his 121 hectare farm.
"It was an unusable piece of land in a low-lying area of the farm," Mr Leahy said.
"I knew a wetland would work well in that location."
Wetlands are known to improve water quality by removing nitrogen, mainly through denitrification, which involves bacteria in the soil converting nitrate in the water to nitrogen gas.
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The wetland is the latest project for Mr Leahy, who has been proactive in improving water quality for the last 15 years.
"I've got several sediment traps and grassed drains already across my properties," Mr Leahy said.
"I'm happy to see that results to date show that the wetland is doing its job."
Griffith University researcher, Dr Fernanda Adame, and her team from the Australian Rivers Institute were tasked with investigating and setting a baseline for the performance of these treatment systems.
"The early indications look positive," Dr Adame said.
"The systems are starting to get the right conditions for the bacteria to remove nitrate from the water, and we are starting to see good levels of denitrification in the soil.
"We assessed soil and water characteristics and potential denitrification rates at the end of last year's dry season. Wetland species, bulkuru and grey rush, were planted at the site and a native, triangular sedge, is naturally vegetating the area.
"As vegetation establishes, the new leaves and roots...provide food to these bacteria, which will result in improved efficiency of this wetland with time - removing nutrients from the water before it leaves the property."
Like natural wetlands, constructed wetlands can also trap sediments, pesticides, metals and pathogens in water.
Wet Tropics Major Integrated Project catchment repair coordinator, Suzette Argent, is responsible for managing and monitoring catchment repair systems and works closely with landholders where trials are taking place.
"Building relationships with growers is imperative," Ms Argent said.
"Getting landholders on board and eager to trial new things is the cornerstone of the project.
"We enjoy taking growers on the journey and sharing the results with them. They can see the difference they're making."
Other treatment systems including bioreactors, high efficiency sediment basins and in-drain wetlands have also been installed and are being monitored on farms throughout the Tully and Johnstone areas as part of the project.
