Chop weeds before they set seed to help deplete the seed bank

Dave Button smiled when asked several years ago what he was building in his shed.

“You’ll see soon,” said the Great Bend, Kansas, farmer as he closed the shed’s door.

• READ MORE: Hard time for herbicides

Button was stymied by Palmer amaranth that resisted every herbicide site of action thrown its way on his farm. He searched for ways to kill it in his fields before Palmer amaranth could set seed to fuel future infestations.

“The most logical way to do that was with a rotary mower that could chop it within soybean and milo rows,” Button says. “I called the original prototype ‘Frankenstein’ because it was modified so many times.”

Now known as the Row Shaver, the unit complements herbicides to control weeds.

“Its purpose is not just killing weeds,” Button says. “We’re also trying to reduce the herbicide-resistant weed seed bank. If we chop the herbicide-resistant Palmer before it pollinates, its seeds are nonviable.”

Less seed translates into fewer weeds, which removes pressure on future herbicide applications.

Besides broadleaves, the Row Shaver also nixes grass weeds and seeds, such as johnsongrass.

Unlike some herbicide applications, no temperature, time-of-day, wind, or buffer restrictions exist.

Button says the Row Shaver also has an edge over cultivation.

“If you cultivate, you kill weeds, but you also kill yield potential because of evaporated moisture and pruned roots,” he says.

Challenges exist for the Row Shaver, such as regrowth following mowing.

“We clipped it [Palmer amaranth] as low as possible and were relieved when it didn’t regrow by the time the soybeans canopied,” Button says.

If needed, a second “shave” is less expensive than a follow-up herbicide application, he adds.

How It Works

The Row Shaver can fit on the front of a self-propelled sprayer.

Sprayers that have automated guidance may precisely traverse rows with no crop damage.

Existing hydraulic controls — supplemented by a safety bar — that enable booms to be raised or lowered also work for the Row Shaver.

Other features include:

• A quick hitch that enables operators to switch a sprayer between the Row Shaver and spray boom in a half hour.
• Various blade lengths that allow rows to be narrowed from 40 to 20  inches.
• Articulating blades that cause the unit to flex if it strikes a rock or pocket gopher mound.

The Row Shaver also can coexist with cover crops, says Button. Height can be adjusted so it clips weeds but still leaves cover crops intact.

Sprayer engine and hydraulic capacity is a balancing act between controlling cost and having sufficient power for the Row Shaver to whack weeds.

“There’s often not enough engine or hydraulic power to drive a Row Shaver with more than five rows,” Button says.

In that case, an auxiliary engine would likely need to be added, as Button did on his demonstration unit.

If an operator uses a corn detasseler as the Row Shaver’s base vehicle, Button says an engine/hydraulic pump addition may not be needed.

“This equates to a huge cost savings, but a corn detasseler also lacks a system to spray or fertilize,” he says. “It all depends on a customer’s needs.”

He also built a complementary machine called the Row Trimmer to remove weed seedpods or flowers above the crop canopy.

“It’s basically a stripped-down combine header — a sickle bar and reel — that floats on top of the crop canopy to also eliminate weed seed production,” Button says.

No Resistance to Steel

The Row Shaver is ready for sales opportunities, Button says.

It’s attracted national and international attention mainly from organic growers, but conventional farmers also are interested.

“Weeds can’t grow resistant to steel,” he says. “Herbicides are always going to have a place,” says Sarah Lancaster, Kansas State University Extension weed specialist. “But we need to find ways to take the selection pressure off weeds. We have to stop the weeds from going to seed. That’s where mechanical technologies like this come into play.”

Herbicide Comeback: Novel sites of action may be on the way

Resistant weeds may have knocked some corn and soybean herbicides down to the canvas.

Yet, much like a scrappy boxer, herbicides aren’t down for the count.

That’s because selection technology used in the pharmaceutical industry may bring new herbicide technologies by decade’s end, says Jacqueline Heard, CEO of Enko, a crop health firm that’s collaborating with chemical firms such as Bayer, Syngenta, and Nufarm.

Target-Based Approach

Scientists searching for new herbicides look for compounds that inhibit critical weed enzymes.

Glyphosate (Group 9), for example, kills weeds by inhibiting EPSP enzymes that interfere with amino acid synthesis, according to Iowa State University weed scientists.

Many herbicide discovery programs examine a potential  inhibiting compound by spraying it on a weed and assessing performance, Heard says.

Enko differs in that it uses a target-based approach based on a rapid screening technology used in the pharmaceutical industry, she points out. “We first identify the pest’s molecular target,” she says. “Then we screen billions of compounds to find those that selectively inhibit [pest enzymes]. That gives us a read on efficacy, selectivity for the pest, and [compound] safety all at the same time. This allows us to solely focus on compounds that will be commercially successful in our pipeline and make it through the regulatory process.”

The wide swath taken by Enko’s screening process also enables the firm to identify novel product starting points in new chemical families that scientists have not yet explored, Heard says.

Enko also uses this technology to combat weed resistance challenges within current herbicide sites for action, such as the target site for glyphosate. To do so, Enko scientists first examine the binding pocket, which is the spot where the herbicide molecule binds to a weed enzyme.

“Usually, enzymatic binding involves a slight conformation change in an enzyme as each molecular bond forms,” Heard points out. “You can think of it like putting on a glove and noticing your fingers reflexively bending a bit, so the glove forms in the right spot around your hand.”

Enko scientists aim to find molecules that can control both resistant and nonresistant weeds, Heard says.

“The interaction [between herbicide molecule and binding site] should work like a lock and key,” Heard says. “The chemical is the key that you want to precisely fit in the lock [binding site].” An airtight bind also enables a herbicide to be more environmentally friendly. “It can then be more effective in lower quantities and have little to no interaction with off-target organisms,” Heard says.

New Compound Coming

Enko has thus far found one novel corn and soybean herbicide for preemergence and postemergence use.

The herbicide likely will be commercialized before 2030, pending regulatory approval.

“We’re bullish on increasing novel and effective molecules in a cost-effective manner, and doing so faster than is done in pipelines today ,” Heard says.