Mills turn weed seeds into dust

19 November 2023 by
Seed Terminator, Kelly Ingram

[January 2023]

Article originally posted on the GRDC GroundCover written by Nicole Baxter. 

Damien Schneider’s investment in harvest weed seed control is part of an integrated strategy he uses to drive down the population of herbicide-resistant annual ryegrass on his farm.
The southern New South Wales grower produces grain and prime lambs with his wife Carissa across 1100 hectares near Culcairn.
He bought a Seed Terminator® in 2019 after trialling and ruling out narrow windrow burning, chaff lining or chaff tramlining.
After analysing the costs, Damien decided a dual-impact mill system was something he could not do without.
“When I saw how much ryegrass seed exited the harvester after cutting half a paddock for hay and harvesting the rest, we had to do something about it,” he says.
Damien estimated that a dual-impact mill would cost about $35 per hectare on average over three years to repay. On top of this cost, he estimated additional fuel consumption for his Case IH 7230 Class 7 harvester of three to four litres/ha.
With herbicides now costing some growers more than $70/ha per year, he views the impact mills as a cost-effective tool for helping to manage ryegrass.
He says there were no problems fitting the mills to his harvester.
When working in canola, the harvester requires more power, mainly because of the extra canola chaff going over the sieves.
The mills work well in cereals, he says. However, he removed them when direct-heading late-sown canola and lupins to prevent green material from jamming the mills.
Damien says his stripper front and impact mills work well together.
“The mills need about 58.8 kilowatts, which is about 80 horsepower, but the stripper front frees up about the same amount of power because the harvester has to process less straw,” he says.
“The efficiency gain we saw in terms of tonnes per hour, fewer harvester hours, less fuel used and reduced labour was phenomenal.”
While Damien was initially concerned that his stripper front might not gather all weed seed escapes, a University of Sydney study with GRDC investment confirmed that there was comparable seed collection to draper fronts.
“When I see weeds in paddocks when harvesting, I lower the front and chase them so that the mills smash the weed seeds into dust,” he says.
“The airflow from the mills enables us to spread a layer of fine dust evenly across the full 12-metre width of our harvester front.”
After three years, he replaced the original mills with a new set before this coming harvest.
While his herbicide use has not yet changed, Damien says he has not needed to plant oaten hay on paddocks for the past two years to reduce the weed seed population.
This year he has chosen to grow the mid-maturing hybrid conventional canola Nuseed® Quartz on some paddocks because the annual ryegrass seedbank is so low.
In the future, he hopes to reduce his reliance on expensive herbicides and add more diversity to his crop rotation with fewer weed blowouts in subsequent crops.

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