While some grain growers have disengaged harvest weed seed control mills in high-yielding crops to improve throughput and speed, others are keeping them working to drive down the annual ryegrass seedbank in every crop.
Weed seed control mills, made by commercial manufacturers, are an add-on fitted to harvesters.
Previous research with GRDC co-investment has shown that a high percentage of weed seed passing through the high-speed mills can be rendered unviable for germination.
South Australian grower Tim Williams and his family, who crop just over 1100 hectares near Conmurra, invested in a Seed Terminator for their John Deere S760 harvester seven years ago.
The family shifted to a John Deere S780 harvester a year later to improve the cleaning area, power and capacity.
In 2022, they upgraded to a newer Seed Terminator and fitted it to a New Holland 9.90 harvester.
Tim says the New Holland twin-rotor machine had more power, a larger cleaning area and an improved discharge beater.
With annual ryegrass, wild oats and bedstraw the top three weeds in the Williams family’s continuous wheat/barley/faba bean farming system, Tim says they opted to move into harvest weed seed control to delay the onset of herbicide resistance.
Gamble pay-off
“It was a bit of a gamble, but it is starting to pay off for us,” he says. “We are now treating our paddocks with fewer pre-emergence herbicides in our disc seeding system, so the decision to buy the mills was validated.”
With milling wheat and barley crops yielding six to eight tonnes per hectare, he says chaff carts or chaff lining are impractical because the residue levels left on the paddock after harvest are too high.
In addition, the window for burning is often not wide enough in his area located 50 kilometres from the coast in SA’s south-east. It is also “a nightmare” to seed through unburnt chaff lines.
Tim and his family investigated the Seed Terminator because they were unsure about the Integrated Harrington Seed Destructor (iHSD) with its hydraulic drive, while the Redekop Seed Control Unit had yet to be released commercially.
Accordingly, the family invested in the mechanically driven Seed Terminator in 2017.
“Back then, the screens fitted to the hammer mills had holes about the size of your finger,” he says.
“But later-model screens, with much thicker holes, massively reduced power use, fuel use and the economy of harvesting the crop.”
Tim and his family opted for the AeroImpact 3 hammer mill screens because they wanted a 99 per cent annual ryegrass kill.
Other options are available, but he did not think they would significantly reduce fuel use or increase the harvesting speed for eight to 10 per cent fewer weed seeds destroyed.
Harvest low
Tim says barley was windrowed, with the cutter bar “on the ground or as low as possible (about beer can height)”, to pick up as many weed escapes as possible.
“We windrow the barley as early as we can, to the point that we might sacrifice a bit of yield, and then pick up the windrows with our New Holland 9.90 harvester fitted with the Seed Terminator.
“We aim to pick up as much of the annual ryegrass as we can in the barley phase of the rotation.”
Unlike some growers who disengage the mills in high-yielding crops, Tim and his family keep them working in wheat and faba beans, fixing issues as they arise.
“We are happy with how it is going now. We haven’t used pre-emergent herbicides on our barley paddocks for three years because prosulfocarb plus s-metolachlor (Boxer Gold®) was our only option with a disc seeder and we didn’t want to cause any crop damage.”
He says the new model Seed Terminator has a Dynamic Straw Streamliner to keep the straw separated from the chaff. This prevents milk thistle, thistle or wild radish from entering the mill, which is ideal for preventing too much straw from overloading the system and causing belt slip.
More information: Tim Williams, timmi24tw@gmail.com