The increasing challenge of herbicide-resistant weeds is prompting some no-till farmers to consider a return to tillage, a move that raises concerns about soil conservation. At the Chickasha Wheat Forage and Field Day, Dr. Liberty Galvin, OSU Weed Science specialist, discussed her research into strategic tillage as a potential tool for managing these problematic weeds in wheat fields.
Dr. Galvin highlighted the reliance on herbicides that contributed to the success of no-till systems. “A lot of our no-till producers became successful no-till producers because of the availability of chemicals. And a lot of producers have used traded crops. So Roundup-ready soybeans, for example. The continual use of those crops year after year after year has created a lot of herbicide-resistant problems, but when you do no-till, you take away all of your mechanical weed control options. So a lot of growers have said, ‘Well, I’m just gonna go back to tillage.'”
As someone with a strong background in soil conservation, Dr. Galvin expressed her apprehension about a widespread return to conventional tillage. “Hearing this now, sometime later, is terrifying because we want to maintain our soil conservation goals, all that carbon. But how do you control herbicide-resistant weeds when you don’t have any more chemical options and you don’t use tillage?”
To address this challenge, Dr. Galvin and her colleague, Dr. Daniel Adamson, a soil and water conservation professor, are investigating strategic tillage practices. “What my colleague, Dr. Daniel Adamson and I are looking at is how much tillage, how frequently you should till, and what type of tillage? So really the intensity.”
Dr. Galvin hypothesized that less frequent, deep tillage might be beneficial. “I think one really deep flip every five years could really help us bury these herbicide-resistant weeds to a depth that will no longer cause us problems.”
The research also considers weed seed dormancy. “If you bury it six inches in the ground and then you don’t do another tillage event for five or 10 years, you might actually be able to get rid of all those herbicide resistant Italian ryegrass plants,” Dr. Galvin suggested, noting the shorter dormancy period of Italian ryegrass compared to some summer weeds.
While the research is in its early stages, Dr. Galvin outlined the initial steps. “Part of our preliminary studies right now is we’re looking at how these seeds move through the soil profile. So before we do a tillage event, we take a soil core, separate it into zero to two inches, two to four inches, and we do a seed bank analysis.”
This involves painstakingly extracting and analyzing weed seeds at different soil depths. Dr. Galvin noted that seeds buried between two and four inches remain viable but often fail to germinate and emerge. The next phase involves tracking seed movement after tillage events. “Now that we’ve done tillage, we need to go back out and collect data to see how those seeds moved through the profile with our different tillage events.”
The research will also examine the impact of tillage on soil health. “We’re also trying to look at carbon-nitrogen movement. How does this 20-year no-till look after a massive tillage event? And is that really gonna mess people up for their coming crop? Is it gonna mess them up for multiple years?” Dr. Galvin explained, highlighting the collaborative nature of the research with a soil science PhD student.
Looking ahead, Dr. Galvin emphasized the need for broader collaboration. “We wanna find people who have been doing no-till for different amounts of time. So, five years, 10 years, 20 years. Just based on the literature, the folks who have been doing no-till for 20 years probably only have seeds in the top inch. That’s great because that means that there’s nothing scary lurking in the depths of the soil.”
The goal is to identify the most effective tillage tools and frequencies. “We want to figure out what the best two or three are, and then the frequency. So we’ll hit it in the fall. We’ll get some good results by next spring. And if we’re really doing good field research, we need to have at least two years, three years would look nicer.” Preliminary data on seed movement is expected to be presented at the Winter Crop School.
Dr. Galvin encouraged growers to stay informed and reach out with their experiences. “Y’all can find me on Facebook, that’s OK State Weed Science. We’re constantly posting about what all of our students are doing, but I do a lot of continuing education courses for pesticide applicators. I’m happy to travel anywhere in the state to talk about this research and herbicide resistance. We’ll be at Winter Crop School this coming December, but I’m also available via phone. Anybody can call me, anybody can send me an email, and I would love to talk to them about their soil concerns or their Italian ryegrass problems. I’m all ears.”
Interested individuals can contact Dr. Galvin at (405) 334-7676.
