Turning creek weeds into compost in the Lower Burdekin

Evolution Mining
Lower Burdekin Water
TropWATER
Local landholders

Agriculture

On-ground work

(none)

Evolution Mining

$200,000

$120,000

1 July 2017

30 December 2018

Freshwater wetlands in North Queensland's Lower Burdekin region provide critical wildlife habitat. Invasive weeds in the area, if left unmanaged, choke these wetlands and reduce water quality to the Great Barrier Reef.

The project is focused on a major weed infestation at Kalamia Creek, near Ayr. The aim is not only to remove the weeds, but also to turn them into a compost to improve soil health and boost local agriculture.

To compost the weeds a permit to transport declared plant material was obtained from Biosecurity Queensland. To reduce the impact of spreading declared weeds and pathogens, the approved permit required the project team to comply with Australian Standards using best practice composting techniques. The project team was required to:

• Ensure the windrows maintained a temperature of 55 degrees plus for over one week then turn and repeat the process.
• Conduct weed seed germination trials on the composted material.
• The Australian Standards align with our desktop investigation in composting techniques, weed seed and pathogen treatment. To comply with the standards the landholder monitored the temperatures of the piles. The compost  sampled weekly for a month and on each occasion the temperature was recorded at over 60 degrees. Seed germination trials were conducted at the Lower Burdekin Landcare nursery.

Produce a beneficial bi-product of weed control activities.  The project has the potential to reduce nutrient run-off from agricultural sites.

The end-goal is to turn the compost into a marketable product to help recover some weed control costs.

There has been three minor challenges. Firstly, pieces of metal (e.g. old rubbish dumped in the area) were being found in the initial pile of the compost which was causing damage to the farmers compost turner. To minimise the impact, the project team bought the farmer a metal detector. The farmer now sweeps the metal detector over the windrows before each turn. If a signal is received, he manually digs into the pile and locates the object. Secondly, the grazier whose property is used to stack the weed material had concerns about potential loss of productive ground and grass cover due to the weed piles and machinery tracks. Access to this property is critical to the success of the project so the project team and the grazier discussed the issues and identified solutions. The outcome was that NQ Dry Tropics provided fencing materials so the grazier could expand his grazing area into a previously unused area.
Thirdly, there is more plant material on the banks than can fit into the composting area. The two possible solutions for this is to either leave it insitu and load it when space becomes available or adapt the composting methods from the current aerobic composting technique to anaerobic. To do this, the project team has been discussing options with a “no turn” composting expert. This solution, if successful, may result in the reduction in loading time, labour and expenses.

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