University of Arkansas weed scientist Jason Norsworthy plans to combine the planting of cover crops with harvest weed seed control tactics this year.
An innovation called the Integrated Harrington Seed Destructor is already pulverizing away in Australia, where farmers are battling herbicide-resistant ryegrass, radish and other weeds in wheat. The Destructor is now part of a U.S. study on the efficacy of harvest weed seed control practices being conducted by scientists in 15 states. So far, it looks to be a smashing success.
Davis found the Destructor is most effective on smaller seeds. “For example, with common waterhemp, which, like Palmer amaranth, has a small seed, we’ve had close to 99.9% efficacy. I haven’t seen any waterhemp seed survive.”
In-combine seed crusher is a smashing success in early research.
“In stationary testing over the winter, we had very high efficacy with the Destructor on the species we tried,” says Adam Davis, research ecologist with USDA Agricultural Research Service, based at the University of Illinois. “On all seven weed species we looked at, we’ve had greater than 98% destruction of the seeds.”
(Progressive Farmer image by University of Illinois)
NO SILVER BULLET. Like any weed-management tactic, weed seed control tactics need to be used before things turn into a total train wreck, Davis adds. “I don’t think you’d be able to salvage a field that’s become unplantable due to weed infestation. But, I think it could help a field from becoming unplantable,” he says.
Its major advantages are that it requires no post-harvest labour, such as burning, and there is no nutrient take-off. An iHSD unit costs about A$165,000 (£93,000).
They returned with funding secured, and Mount Gambier-based outfit De Bruin Engineering was licensed to build the first commercial machines in 2009.
“When it goes through the mill, the 40kg renders down into a hatful. They took all the chaff away in little brown paper bags and came up with a ‘kill curve’,” he says.
Harvest weed seed control kit – what are the options?
He adds that North America is somewhere that the machine could really take off, with herbicide resistant weeds – particularly to glyphosate – an increasing problem.
The machine uses a chaff and straw transfer system from a chaff cart, which moves the material from the back of the combine to the cage mill, driven by its own 160hp diesel motor. The pulverised material is then spread back on to the field.
After discussing the future of resistant weed management with Dr Powles, he had mentioned in passing his experiment with the cage mill – and within 24 hours received a phone call.
Similarly, in controlled traffic farming systems a chaff deck can intercept and place the chaff fraction behind the wheel tracks of the combine and in the rows, leaving the chaff and weed seeds to decompose. A retrofit kit will cost about A$15,000-A$20,000 (£8,450-£11,300).
We feature some of Davis’ earlier work on the Managing Weeds for Healthy Kids project site. He led a team whose research, published in 2012, documented that increasing cropping system diversity effectively suppressed weeds while maintaining yields and profit, when compared to conventional, herbicide-reliant weed management systems.
Instead, Borel highlights big new projects looking at large-scale patterns in weed resistance, and at how old farming techniques like crop rotation and cover crops can help prevent the spread of resistant weeds.
But in reality, this machine is towed behind harvest equipment to capture weed seeds and crush them into inert mush, thereby reducing the spread of resistance.
This stark analysis is part of the title of a new Scientific American deep-dive into efforts to battle weed resistance. The author, Brooke Borel, summarizes the latest science, including research done at North Carolina State University. Scientists at NC State reached the sobering conclusion that “[there is a] considerable chance that the evolution of pest resistance will outpace human innovation.” In other words, the likelihood that we will be able to “herbicide science” — or spray — our way out of current crises rooted in the spread of resistant weeds is slim.
The next step will be convincing farmers to change their habits. Quoted in a piece on the Harrington Seed Destructor, Davis urges that “every farmer needs to be thinking about how to do this now…There is no path forward for chemical-alone weed management. We have to reduce our reliance on herbicides because there’s nothing new in the pipeline.”