Seed Impact Mill Technology Hammers Herbicide-Resistant Weeds

Seventy-five-thousand dollars is a lot of money to put into a tool whose only job is to obliterate weed seeds. 

But buying such a tool – called a harvest weed seed control system (HWSC), which uses seed impact mill technology – and installing it on your combine can be a good investment, says one Texas farmer who has done just that. The one caveat for his endorsement of such tools? You need to have at least one significant herbicide-resistant weed that is gaining the upper hand in your fields.

“Where you have a major weed resistance problem and there's no other effective means (to control it), I think this is a no brainer from what I can see,” says Rodney Schronk, who grows dryland corn, cotton, wheat and sunflowers about an hour south of Dallas.

Schronk is going into year three of using a Redekop Seed Control Unit. The three weed species he is most concerned about and is targeting with the unit are Italian ryegrass, redroot pigweed and Johnsongrass. 

While he suspects all three weeds exhibit some degree of herbicide resistance on his farm, the Italian ryegrass is particularly concerning. “It has very strong resistance to glyphosate,” he says.

Schronk says his No. 1 reason for purchasing the Redekop was to run it during hard and soft red winter wheat harvests.

“It has worked flawlessly in that scenario,” he says. “We've had no trouble whatsoever.”

Three Systems Available Today
Schronk first heard about the Redekop and what it was capable of doing from his son who had learned about it from one of his professors at Texas A&M. The Redekop is one of three HWSC systems available commercially today. The other two are the integrated Harrington Seed Destructor (iHSD) and the Seed Terminator.

The basic premise of these tools, called seed impact mills, is they destroy weed seeds during harvest. As plant material moves through the combine, the mills damage weed seeds and render them non-viable. 

While each of the three systems has some different features between them, each one is effective, according to Michael Flessner, Extension weed scientist at Virginia Tech.

“All three brands are very effective at killing the weed seeds with, generally, over 98% kill,” says Flessner. “The one weed that we've had less than that percentage of control with is Italian ryegrass, where we're seeing more of a 90% to 95% kill. So, they are very effective.”

Flessner led a farmer panel discussion on HWSC systems using seed impact mills on behalf of GROW (Getting Rid of Weeds) in December. The discussion is available to watch in full on YouTube here. 

Few On The Farm, So Far
Flessner says he estimates there are about 50 HWSC systems on U.S. farms in operation today. He believes the $75,000 price tag is the main reason more have not been purchased. 

“It is somewhat of a sticker shock when you first hear that, but when you spread that across acres, the price comes down substantially,” he says. “In Australia, they kind of equate it to about the price of a cheap herbicide pass.”

Flessner estimates about 1,250 seed mill units are currently used on farms in Australia, where weed resistance problems are often as severe or worse than those in the U.S. 

While the HWSC systems are effective, farmers interested in purchasing them will want to consider some of the pros and cons. Here are some of the factors the farmer panel discussed:

1. The systems work better in some crops than others. Along with that, green plant matter often leads to plugged up systems. 

“They don’t like green, period,” says Nick Druffel, who farms with his brother, Dale, near Uniontown, Wash. The brothers grow wheat, peas, lentils, chickpeas, and from time-to-time, some barley. 

They purchased a Seed Terminator to address some of their most problematic weeds, such as Italian ryegrass, wild oats and dog fennel. 

“When it comes to cutting lentils, we have to change out our mills to a high-flow mill; otherwise, it’ll plug instantly,” Nick says.

“We kind of have to pick and choose a little bit. If (the crop) is too green, even in green wheat, it will plug. But for the most part we're getting we're getting a handle on it,” Nick adds.

Schronk says he had a similar challenge with the Redekop in sunflowers. “Where our sunflowers were very dry, it worked just fine. But the second we got into some sunflowers with a little bit of moisture, it stopped up.”

2. The systems can have significant horsepower requirements. “It takes a minimum 100 hp to run it,” says Nick Druffel of the Seed Terminator. “Fuel-wise, you burn a lot of fuel. We figure it cost us about $4 an acre.”

Schronk adds that significant plant matter in big crops can slow the harvest process, when the systems are used.

He says the Redekop performed well in his 2022 corn crop but that a “good” 2023 corn crop ate into his available horsepower.

“We really like using (the Redekop) in corn, but this year it was slowing us down tremendously. So we had to disengage it to get through our corn crop just because of speed,” he says. “We’ll have to go to a higher horsepower combine to meet those requirements.”

3. Herbicides still play an important role in weed control. The Druffels say the Seed Terminator they purchased is another tool in their toolbox that is helping them deplete their weed seed bank – their ultimate goal. They believe that goal will require multiple practices to achieve, including herbicide use.

“When we went into this we didn't change anything that we did,” Nick says. “We still spray the same, we don't cut rates, we just basically added another tool to our toolbox to help with the weed situation.”

Flessner encourages farmers evaluating whether to purchase an HWSC system to consider the kinds of weeds that are escaping their current control methods. Many are herbicide resistant.

“These aren’t just any old weed seeds,” he says. “These are weed seeds that have beaten whatever you've thrown at them, whether that was your herbicide program, crop competition, or whatever. They've kind of won that battle. And currently, we are rewarding them across millions of acres in the United States and around the world with a conventional harvest. These (tools) can really put a stop to those weed seeds before we spread them out around the farm.”

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