Chemical, mechanical and physical weed control is the future


University of Missouri tests show that 70-110 pounds of grain rye planted per acre in the fall and completed shortly after planting soybeans in the spring can reduce water hemp stands by 50-70% for 28 days after planting.

Cover crops supplant weeds for light, water and nutrients. The biomass of completed cover crops mitigates weed emergence.

“Growing weeds are delayed, giving farmers more time to apply a post-emergent herbicide,” Steckel said.

John Lindamood agreed with Steckel. The Tiptonville, Tennessee farmer said cover crops in his fields choke weeds or delay emergence so he can apply herbicides in a timely manner.

“The goal is to keep weeds at bay until the crops cover, then you are free to go home,” he said.

At times Lindamood has said he has been able to reduce herbicide rates through effective weed control by cover crops or eliminating a pass of herbicide. With soaring prices for agricultural inputs and some hard-to-obtain herbicides, cover crops can help allay both concerns, although seeding and disposal of cover crops is far from free.


Lisa Behnken, a recently retired University of Minnesota (U of M) agricultural extension specialist, believes the message that weed control can’t just come from a jug is getting across.

On average, 30% of the 3,200 Minnesota farmers surveyed by the U of M from 2017 to 2020 admitted to pulling weeds.

“We have to be creative to outsmart the weeds,” Behnken said, which could mean reverting to control measures before herbicides become the main weapon.

She recommended mapping weed escapements to focus control efforts the following year. Mowing streams and ditches is also an effective pre-harvest weed control tool. Combines can catch weeds from the edges of fields or streams and spread weed seeds. While not desirable, Behnken said it might be necessary to mow small weed-infested crop plots to prevent weeds from going to seed.

“Herbicide resistance is here to stay, but there are control options that can work on different farms,” she added.


Many farmers who were not involved in organic production sold or parked mouldboard plows and row cultivators decades ago. Circumstances may require growers to use the tools again for weed control.

Barber said turning the soil to bury weed seeds or pull weeds out of the soil during the growing season can be effective control measures. He does not suggest doing it on every acre, but on certain areas where it is needed.

“I know that deep plowing goes against conservation practice and thinking, but it may be necessary,” said Barber.

“One of the weaknesses of amaranth is that the longevity of seeds in the soil is quite short, like three to five years,” he continued. “It won’t completely reduce amaranth, but it will significantly reduce them.”

For farmers who no longer own a plow or tiller, used parts are available for sale. Marzolf Implement Co., in Spring Valley, Minnesota, for example, has several options.

According to the dealer’s website,, a Case-IH 720 six-bed plow is available for $ 5,000 and a Koen 4RW row cultivator can be purchased for $ 1,200.


The Seed Terminator and Integrated Harrington Seed Destructor destroy weed seeds at harvest so they cannot germinate in the future. Both systems are combine harvester attachments that use hammer mills to pulverize plants, including weeds and weed seeds, after the threshing process.

Weed seed killers are widely used in Australia. A handful of machines are tested and used on farms in the United States.

According to a study from the University of Missouri, the success rate of the Seed Terminator in destroying aquatic hemp seeds is over 90%. Similar results were found in the Harrington university tests. However, it takes many years to reduce the weed seed banks.

“If you get something that keeps about 90% of the weed seeds that go into a combine from going back into the ground, that will be very helpful,” said Kevin Bradley, weed specialist at the University of Missouri. .

Learn about the university’s work on destroying weed seeds and watch a video of the Seed Terminator in action at….


Editor’s Note:

This article originally appeared on on November 13, 2020, as part of our Conquer Your Soybean Costs series. You can read the original version here:….

Matthew Wilde can be contacted at [email protected]

Follow him on Twitter @progressivwilde

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