Wheat farmers are considering attaching seed impact mills to the back of their combines during harvest to pulverize chaff and weed seeds.

The devices were the subject of a recent webinar hosted by Getting Rid of Weeds (GROW), scientist-led national network coordinating research to help farmers fight herbicide resistance.

“These aren’t just any old weed seeds,” said Michael Flessner, Virginia Tech extension weed science specialist. “These weed seeds have beaten whatever you’ve thrown at them that year, whether that was your herbicide program, crop competition, they’ve kind of won that battle.”

Three models are currently commercially available. All brands are over 98% effective at killing weed seeds, with only Italian ryegrass seeing a reduced kill rate, about 90% to 95%, Flessner said.

The technology was developed in Australia, where it is commonly used, said Drew Lyon, Washington State University weed science professor.  About 30 units are running in the Pacific Northwest, he said.

‘Sticker shock’

The mills cost about $75,000.

“It is somewhat of a sticker shock when you first hear that, but when you spread that across acres, the price comes down substantially,” Flessner said.

Nick and Dale Druffel, dryland farmers in Uniontown, Wash., run one combine with the mill where they have weed pressure, and run another combine without it.

“The initial investment up front is huge,” Nick Druffel said. “If you’re going to buy one, you better hopefully plan on it to be a five- to eight-year return on your investment.”

Green crops

They have to change to a higher-flow screen for green crops, or else the equipment plugs “instantly,” Nick Druffel said.

“If it’s too green, even in green wheat, it will plug,” Nick Druffel said. “For the most part, the last two years for us have just been a huge learning curve.”

“Anything green is a problem,” Texas farmer Rodney Schronk agreed. “If you’re harvesting a crop that tends to have a lot of wet stalk in it, you need to think twice until they get the technology more refined.”

Combine performance

Schronk said a combination of the mill and a good corn crop ate up so much horsepower on his combine he had to disengage the device for speed purposes. He estimated he slows from 5 mph to 3 mph. 

“It’s a substantial drag on your speed in good wheat,” he said. “If this is a long-term solution, what we will need to do is go to a higher-horsepower combine to meet those requirements.”

It takes a minimum of 100 horsepower to run the device, Nick Druffel said.

“You burn a lot of fuel,” he said, estimating the device costs $4 per acre in fuel to run in higher-yielding wheat.

Advice for farmers

The device is an extra tool for weed control, reducing pressure, but not likely to replace herbicides, the researchers and farmers say.

“The jury’s still out,” Lyon said. “It’s your early adopters right now who are taking it on.”

Two years in, Nick Druffel thinks he would recommend it.

“Hopefully, in a couple more years, I can say a ‘Yes or No’ answer,” he said. “It’s up for debate.”

Schronk also needs a few more years or two more before he’s certain that the concept works and is worth the investment.

“Where it’s a marginal problem, it’s a little bit more difficult to say that yet until I see l the longer-term studies,” he said. “But when you have a major resistance problem and there’s no other effective means, this is a no-brainer, from what I can see.”

https://growiwm.org/farmer-forum-recap-using-seed-impact-mills-for-weed-control/