Will resistant wild oats bend to the plow?

CAMROSE, Alta. — Tackling herbicide resistance in wild oats may require a look back to farming methods long ago discarded, including plowing.

“It takes a while to wrap your head around plowing when you have not tilled for 35 years,” said Nathan Eshpeter, project manager for the Resistant Wild Oat Action Committee, a subcommittee of the Canadian Weed Science Society.

Eshpeter, also a farmer, has seen firsthand the expanding resistance of weeds to herbicides. A 2020 study estimates 69 percent of wild oats have herbicide resistance, up from 20 percent in 2000.

Those numbers have alarmed farmers and led Eshpeter and his father, Ken, and retired weed scientist Neil Harker to propose new ways to deal with herbicide resistance, especially in wild oats. The action committee consists of farmers, researchers and agronomists from across Western Canada, all seeking a solution to wild oat herbicide resistance.

Funded by a group of prairie crop commissions, the committee initiated research this spring that includes an inversion plow trial in 12 fields around Rosalind, Strome and Daysland in Alberta. The trials were in several areas known to have a heavy wild oat load and two areas with lesser infestations to act as a test or control. The idea was to see if burying the seed-rich top layer of soil would provide effective wild oat control.

“Our goal is to see how well (plowing) can bury residual weed seeds at the residual seed bank,” said Eshpeter. “Can we bury them and does that reduce their viability?”

The trial and other research works on the theory that burying the weed seeds will break them down, reduce their number and viability, and break their dormancy.

The initial review reveals as many questions as answers.

In the trials, plowing was the only change to the plots, which otherwise were managed like the rest of the field. If there was a pre-seed burn or granular herbicide treatment on the rest of the field, it was also done on the trial plots, which ranged from 70 to 200 feet wide by 500 to 800 feet long.

The committee rented a Kuhn 152 moldboard plow with a skimmer to turn the topsoil in the test plots. A skimmer is a small moldboard plow in front of the main moldboard. It removes the first layer of soil, where the main wild oat seed bank would be, and throws it into the adjacent furrow before it is buried by the plow behind it.

“The hope is that the top layer full of weed seeds will be put eight inches down,” said Eshpeter.

However, the layer isn’t buried perfectly or uniformly.

The plow design turns the soil strip on an angle. Some of the seed is buried three inches deep and other seed is buried eight inches deep.

Initial results are a mixed bag. Few wild oats emerged in some plots but on others there was a thin row where the topsoil wasn’t deeply buried. Other plots had wild oats scattered throughout.

“The initial emergence is based on anecdotal research of early seed emergence. The next step is what it looks like as the crop starts to head.”

Eshpeter said researchers need to see whether simple plow adjustments could produce a more consistent burial of seed, whether the findings are independent of the plow and whether the deeply buried seeds remain viable and will emerge throughout the summer.

“It is at a proof-of-concept stage. There are lots of things to work out before we can say this is a viable way of doing things,” he said.

If their theory proves true and the machine can turn soil consistently, maybe plowing every 10 years or so will be enough to reduce wild oats and other weed seeds.

“This isn’t your grandpa’s plow, designed for tillage. This is a plow that does inversion of weeds at the surface.”

Eshpeter said he feels he and other farmers have been “backed into a corner,” with few options to deal with the growing number of herbicide-resistant weeds.

“Do you spend $60 to $80 an acre to control weeds or do you come at it from a whole different angle?”

The research will also test different fall and spring tillage practices to encourage wild oat emergence more consistently and it will consider weed seed destruction at the combine.

“None of these things are simple and are a universal silver bullet, but we hope all will be a readily acceptable tool in the toolkit as part of an overall management strategy,” Eshpeter said.

The problem of herbicide resistant weeds is not limited to a small group of farmers who have misused chemicals by repeatedly using the same ones. It is a problem facing almost all farmers.

“We have managed herbicide use on our farm and we still have places where if you don’t use three seed treatments, it’s tough to squeak a crop out of the farm. It is a jungle of wild oats,” he said.

“This is a big, big deal. The population of oats, whether they are resistant or not, is kind of out of hand. Herbicide rotation is an important tool as well, but if it is the only (tactic) we use, we will wear them out.”

Eshpeter plans to undertake a literature review to see what knowledge is available on wild oat viability and dormancy and its reaction to plowing.

He will also survey a group of farmers on their management practices and awareness of the problem. They will be asked to scout their fields and send wild oat samples for herbicide resistance tests.

“We want to open up the discussion about the extent and existence of wild oat resistance,” he said.

As part of a larger awareness campaign, a video will be made this summer featuring farmers talking about herbicide resistance on their farms.