By-pass mode can extend impact mill life
Esperance Sandplain growers Stewart and Jessica Wallace of Wallbrook Farms started out with chaff carts in 1997 to collect wild radish and annual ryegrass seed at harvest. After two decades of harvest weed seed control, Stewart swapped the chaff carts for a seed impact mill when he upgraded his harvester in 2019.
He finds that the Redekop SCU mill, coupled with a MAV chopper, is doing as good a job or better than the chaff carts – without the need to burn the chaff.
“In our high rainfall environment, it was often difficult to burn the chaff heaps, and our non-wetting sands need as much organic matter as possible. So it is really beneficial to retain all our crop residues on the paddock while still driving down the weed seed bank,” says Stewart.
The Wallaces have a 3000 ha cropping program with roughly 30 per cent each of wheat, canola and barley. Stewart uses the mill in all crops, although he expects to be able to set it to by-pass mode in the canola phase because the crops are usually very clean at harvest.
“In the canola we implement several weed control tactics, and if the crops are clean, I am confident that we could save some wear and tear on the mills by switching to by-pass mode,” he says. “We will make that call based on what we see in the paddock at harvest time.”
Stewart says they usually start harvesting canola early, often around 11 per cent moisture when the stalks are still green. This brings harvest forward and they are partners in a local grain drying operation, allowing them to reduce the moisture level of the grain after harvest.
In 2021 and 2022, Stewart ran an integrated Redekop SCU on a John Deere S790 harvester with a MAV chopper. The mills operated well in all crops, including the canola, targeting their three main weeds – annual ryegrass, bromegrass and wild radish.
“Cutting the crops low to put everything through the mills and the chopper makes it much easier to manage straw at seeding,” he says. “The chopper spreads the crop residue quite evenly across the 12 m swathe behind the harvester in our controlled traffic system.”
Stewart has observed that harvest weed seed control has selected for the early shedding trait in some weed species. He has found that the strategic use of Roundup Ready canola in paddocks with brome grass has effectively kept weed numbers low.
Another tactic Stewart has employed is growing shorter stature barley varieties that produce less biomass without compromising yield. He says getting the weed seed into the mill is easier because there is less bulk to process.
This year, Stewart will be running a Redekop SCU on a new John Deere X9 harvester.
Redekop SCU representative Marney Strachan says grain, sand and overall throughput all affect the life of weed seed impact mill components.
“We have simplified the drive mechanism for the SCU mill, so there is less maintenance required than earlier models,” he says. “The new belts are made of a compound material that has extended the belt life significantly, and the new straw divider stops ropey green material from dropping onto the shoe.”
Harvest weed seed control is one of the WeedSmart Big 6 tactics to limit the impact of weeds that have evaded herbicide during the cropping phase. Three companies offer seed impact mills in Australia, and all are WeedSmart partners.
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