Agronomy professor and cropping systems specialist with K-State Research and Extension, John Holman, sees changes ahead as far as using tillage as weed control. He’s heard of farmers—who swore they’d never till again—“dragging old implements out of the tree row.”
Holman spoke during the Southwest Research and Extension Center’s Tillage Field Day June 13 in Garden City, Kansas.
“We have a site where the last five years we’ve been comparing some no-till to what we call strategic, or occasional, tillage,,” Holman said.
Bob Gillen, administrator at the center, said tillage is becoming more relevant and important as weeds become more of a challenge.
“Certainly tillage is one of the foundation decisions that producers have to make,” Gillen said. “Tillage, crop rotation, weed control—we can make a long, long list but tillage has to be right up in there. Especially over the last several years.”
Gillen said crop production has been going in one direction, and things have changed “as they always do.” Farmers and researchers alike are going to have to change the way they think when considering whether to re-use tillage.
“We thought we had that going in one direction and I think tillage is a very relevant topic,” Gillen said. “We’ve had a lot of questions about it over the last several years.”
Comparisons
Alan Schlegel has been working on cropping systems in Tribune, Kansas, for many years. In his studies, he’s compared no-till, conventional till and occasional tillage. Schlegel is the agronomist-in-charge, soil management at the Southwest Research and Extension Center.
“When we first started this, the first five years we didn’t see much response to no-till,” he said. “The next five years we’ve seen quite a bit. This follows that same pattern. It takes a while to get the benefit.”
The change in the soil properties isn’t instantaneous. Typically, Schlegel used wheat, sorghum, fallow rotations in his research and wheat often showed a positive response, while for sorghum it wasn’t as pronounced.
“Even that short term, no-till is 50 percent higher yields with continuous versus the short term,” Schlegel said. “We thought we could get a really good response to no-till.”
The yields might not be as attractive if herbicide cost is just too much.
Economics
Monte Vandeveer, Extension specialist, agricultural economics at Garden City, put the “dollars and cents” to the numbers Schlegel talked about. For him, the biggest difference between the systems shows up on the sorghum side.
“Does the sorghum yield advantage we get from no-till kind of swamp everything else? Right,” Vandeveer said. “So then when we look at the returns over the entire wheat, sorghum, fallow for each system, we get kind of the same result we saw on the sorghum side.”
The benefit they observed from the advantage on sorghum yields makes the no-till system look a lot better.
“That’s not just on the average, most of these years you see our no-till returns looking a little bit better,” Vandeveer said.
In the first study comparing no-till, conventional till and reduced till, it was the yield advantage for grain sorghum that carried the overall advantage in that system over time.
“When we look at the reduced till, we didn’t see a huge difference on the yield side,” Vandeveer said. “Maybe there is a small advantage to tillage after sorghum or before wheat if we were comparing those two treatments.”
The cost of the extra tillage came to about $11 an acre and the added grain yield translates into maybe two or three bushels of wheat or about three bushels of sorghum.
“How would we compare that to the cost if we were going to make an extra herbicide treatment in there instead,” Vandeveer said. “A lot of ideas in there to chew on and talk about.”
Resistance
One of those ideas isn’t new. Weed Management Professor Curtis Thompson, Extension and Research at K-State, said for him the irony is when he started in Extension in 1993, the focus was merging from a wheat-fallow system using no-till or reduced tillage to increase crop intensity and profitability. He spent a lot of time focusing on weed management in no-till.
“Back then glyphosate worked well as a substitute for tillage,” Thompson said. “It’s kind of ironic, because today we’re talking about the effects of tillage on weeds and weed seed.”
Back then getting into no-till was a little expensive, but farmers found a way to be creative and keep the weeds in check. That was until resistance to certain chemicals became prevalent.
“For a while as a weed scientist I was concerned that I was going to be out of business,” he said. “No need for a weed scientist if you have a glyphosate that kills all those weeds. But, trust me, the last several years we’ve been fully employed.”
Thompson said he understands why weeds are resistant and how to control them by using tillage, but a farmer first needs to ask why till. Financially, the days of tilling just to till are over. Preparation of the seedbed is important, and he’s always strongly suggested, as a weed scientist, to start with a good, clean seedbed.
“But I’ve heard more than once, the only way to manage these weeds is with a cultivator. Work them black,” Thompson said. “To be honest with you, it doesn’t control them. You kill the vegetation. But everything comes back. So it isn’t necessarily an effective way to manage perennial weeds.”
Another thing he’s heard about tillage through the years is there are no steel-resistant weeds. Annual weeds are killed by the tillage. Thompson isn’t so sure.
“Last summer I saw fields that were full of palmer amaranth that had been tilled once or twice and guess what, they were still full,” he said.
Tillage effectiveness depends on weed species; the size of the weeds; when tillage occurs and the environment post-tillage.
Thompson said he doesn’t agree tillage has an affect on the crop herbicide program simply because turning the soil buries the seeds deeper. Moldboard plows rolled the seeds under, and were effective in controlling at least the small seeded weeds. But on the second pass with the same plow, those seeds were rolled back up.
Tillage is a disruptive process. It uproots plants that are small enough, or even buries them. Weather following needs to be effective to make the whole process a successful one.
“Again, to damage the integrity of that weed so that when we get that 100 degree weather and a little breeze we actually get pretty good control,” he said. “The other thing I think we need to think about is what is it doing with the weed seed laying on the soil surface?”
There’s pros and cons to burying the seeds, especially when there’s more than one use of tillage.
“Our large seeded weeds benefit from tillage because we move them through the profile to increase that soil to seed contact,” Thompson said. “So they can take enough moisture on to grow and germinate. And yet there are some weed seeds that get buried below that germination zone and will lay dormant until they get moved closer to the surface where they can grow again.”
Tillage can provide effective control over annual herbicide resistant weeds if needed, but Thompson still contends it can be done with no-till. Herbicides can get expensive, but they can be used effectively.
“We know that tillage system does have an effect on our weed species that are out there in a no-till system probably does favor our smaller seeded weeds—the pigweeds, the kochia and summer annual grasses,” Thompson said.
As the old iron equipment used to be a trusted friend in the days of tillage, there are some allies in the no-till field too.
“We do know surface residues are our friend,” Thompson said. “It’s our friend from the standpoint of moisture conservation, reducing erosion, but it’s also our friend from the standpoint of weed control.”
Kylene Scott can be reached at [email protected] or 620-227-1804.
