Slicing weeds down to size

Cereal stems move unscathed through the CombCut’s comb-like knives, while broadleaf weed stems are cropped close to the ground. Photo: Jennifer Blair

Organic grain growers have been snapping up CombCut machines ‘like crazy‘ — but they’re also a way to control herbicide resistant weeds

By Jennifer Blair
OrganicBiz staff 

A new piece of machinery is helping crop growers control broadleaf weeds on their farms — especially on organic operations.

“Organic growers are buying these CombCut machines like crazy,” said Steve Shirtliffe, a professor of plant sciences at the University of Saskatchewan.

“There’s a real buzz in the organic farming community. I’ve never seen equipment being taken up this quickly by organic farmers.”

Developed in Sweden by Just Common Sense — a green technology company — the CombCut has a series of comb-like knives on a rotating bar. Thin-stemmed crops, like wheat and barley, move through the knives unscathed, while thick-stemmed broadleaf weeds, such as thistle or volunteer canola, are clipped close to the ground.

“What they’ve found in Europe is that it works well for mustard and thistle — any broadleaf weeds that tend to be erect or tall,” said Shirtliffe, who demonstrated the equipment at canolaPALOOZA earlier this summer.

When you’re looking at non-chemical methods of managing weeds, it’s an integration. – Breanne Tidemann

“The cereal leaves can bend and go through it, and you can clip the weeds like mustard and Canada thistle that have the thick stem.”

The CombCut — which retails for about $20,000 for the six-metre-wide model — is mostly used in organic production, said Shirtliffe, who has been testing the equipment for about a month.

“For organic farmers, wild mustard and Canada thistle are pretty much their two biggest weed problems,” he said.

But conventional producers could also benefit from using the CombCut, particularly if they’re starting to notice herbicide resistance in their fields, said Breanne Tidemann, a graduate student at the University of Alberta.

“If conventional farmers would adopt it, that would be great because you could extend the lifetime of your herbicides by having these alternate measures,” said Tidemann. “The CombCut is being used by organic producers actively in their organic rotations, but for us, it’s really looking ahead and saying, ‘When our conventional farmers have that problem, what are they going to do?’”

The CombCut reduces the seed set of broadleaf leaves, and over time, producers will seed fewer weeds in their fields.

“It’s not just managing your weed competition but also managing how many weed seeds go back into your seedbank to try and reduce the amount of weeds that are there,” said Shirtliffe.

“But what they found in Europe was that one application isn’t going to do a lot. It takes several throughout the year. You have to start early and keep on it. For something like thistles, it would take at least a couple years to get them beat back.”

The CombCut gives producers another tool in their toolbox for dealing with weeds, added Tidemann.

“When you’re looking at non-chemical methods of managing weeds, it’s an integration,” she said. “You need multiple tools because none of our tools are as effective as a single herbicide application.”

The CombCut removes weeds early in their lifecycle, she said, and when combined with harvest weed seed management tools — like chaff carts or the Harrington Seed Destructor — producers can hit weeds “at two different points in their lifecycle to try to drive that population down.”

“Anything that we miss (with the CombCut), we’re trying to capture what’s left with harvest weed seed control and prevent it from going into the next year,” said Tidemann.

For conventional producers, using a new piece of machinery to control problem weeds might not be worth the expense and hassle — “but if your herbicide’s not working, what else are you going to do?”

“In the short-term, we’re trying to figure out what could work so that when a producer does have a resistance problem, we have something to offer him or her as a solution,” said Tidemann.

“We’re trying to get a feel for what will and won’t work before we’re actually at that point.”

This article was originally published on the Alberta Farmer Express