MOBILISING THE MOSSMAN AND MURRAY PROJECT
VEGETATED CANE DRAINS – THE “NO FRILLS” WETLANDS
4 NOV 2022
The legacy of denitrification trials in an ambitious reef water quality project is flowing into the toolbox of practices that farmers are using to improve the quality of water leaving farms.
The ecological benefits of restoring wetlands are long established, but the characteristics that vegetated drains share with wetlands means they can act as a cost-effective system for treating nitrate.
Farm drains retrofitted to enable nitrate removal were first trialled during the Wet Tropics Major Integrated Project, which concluded in 2021. While results varied between systems depending on the ecological development, environment and dissolved inorganic nitrogen signature, the project was able to demonstrate the effectiveness of vegetated farm drains at removing nitrate when they have the right characteristics.
Mossman Ag’s Rebecca McHardie says that the work required to retrofit drains is far less than constructing or restoring a wetland, making vegetated drains more accessible to farmers. “Considering the amount of farm drainage we have in the Wet Tropics, the potential is exciting,” said Mrs McHardie.
Jack Murday is one of several farmers in the Mossman region giving farm drains a makeover. He and his father have reprofiled one of their drains to be wide and shallow, and constructed rocky retaining dams to further slow down the flow of water. It will be seeded with native grass and sedges.
“Before we retrofitted the drain, it was narrow, steep and eroding, and the only option to maintain it was to spray it out. The new shape means we can slash rather than use spray, preserving the nitrate and sediment-capturing vegetation” said Mr Murday.
“As proven elsewhere, having the right density of vegetation in the drain will trap sediment and treat nitrate in the water. It aligns with our farm’s long term management plan to reduce our inputs and improve production, sustainably.”
The drain will treat 9 hectares of cane paddock on Mango Park and contributes to the total of 200 hectares of cane farming land being treated by vegetated drains in the Mossman area.
Vegetated drain projects in Mossman have been made possible through a Prod180 grants round designed by Mossman Ag with input from local growers. It is part of a larger project, Mobilising the Mossman and Murray, delivered by Terrain NRM and funded by the Australian Government’s Reef Trust.