Levi Lyle calls it "one-pass farming." It isn't something he's been able to do on all of his fields, but it's a goal he's shooting for — limiting his fertilizer and weed control inputs down to a single pass with the planter and a front-mounted roller-crimper he built from a salvaged row cultivator frame.
Lyle, 42, started cover cropping about 10 years ago after he moved back to his family's farm in Washington County, Iowa.
"Shortly after I moved back to the farm, we started hearing more from growers in the area, like Steve Berger, and he had been doing it for decades over in Wellman. Growers like that have all this experience under their belt, and have provided a local resource," he says. "That helped give me a foundation to go in and seed 40 acres of cover crops and just assess it. Some of it came 1 acre at a time. That led to planting soybeans into green rye."
Terminating while planting
At the core of the one-pass system is the roller-crimper. Lyle was introduced to the roller-crimper concept before he came back to the farm — when he was working as a high school biology teacher.
"I learned about it 15 years ago and wasn't even back on the farm yet," he says. "When I got back and started doing organic inspections, it suddenly came back to me. I could see the frustration on growers' faces when I would visit them. I saw farmers struggling on the soybean side with weed control. I thought something else needed to be done."
In addition, there weren't many roller-crimpers available in the Midwest. So, using a design borrowed from USDA, he worked with a local manufacturer to build his own roller-crimper, with blades arranged in a chevron pattern — angled in a "V" on the roller — to prevent bouncing and keep the blades in constant contact with the soil. He now leases the roller to other farmers in the area.
"The chevron blade allows it to make constant contact with the soil, and the weight is dispersed," Lyle says. "The chevron design is so that if you have that V shape, you make it so the machine has a smooth ride; it doesn't bounce around like a straight-bar machine. It's also a front-mounted implement, which is why it works so well in terms of cost savings.
"It keeps the rye in contact with the soil, and that way, the rye terminates slowly — it doesn't chop it off. It allows the rye to lie as a mat to suppress weeds," he says. "Once rye hits anthesis, it will die when the stem is creased. It will die very slowly over six weeks and provide good protection against weeds. It started out just on organic, but we realized it's working on the conventional side, so we've used it more on the conventional side as well."
By planting soybeans — and in a few cases, corn — into a green cover crop, along with 10 years of cover cropping, Lyle has seen some significant returns.
He has noted data collected in 2019 and 2020. He planted soybeans into a standing rye cover crop before terminating the rye with the roller-crimper, and corn into terminated rye residue. The analysis was conducted on a per-acre basis and extrapolated across the 250 acres where he had seeded rye. The total net returns were $39.28 per acre on corn and $11.33 on soybeans. This eliminated his preemergence herbicide applications in soybeans, a savings of $21.85.
"We planted the corn green, and terminated rye after it. That's $25 per acre of rye we put on. We planted 2 bushels of rye per acre," Lyle says. "Those net returns are mostly due to eliminated passes and the reduction in herbicides used."
There were greater savings in corn — and Lyle attributes this to spending $37.33 less per acre on fertilizer. He's also working toward reducing fertilizer applications on the rest of his corn acres. The goal is to minimize the leaching of excess fertilizer by holding it in the cover crop, therefore improving fertilizer efficiency.
In 2019, Lyle's farm received abundant rainfall in May, preventing him from terminating until rye was far enough along to produce mature seed as it lies in the field. This resulted in 60 acres of volunteer rye, which he partially credits to the nitrogen released later in the season.
"We're growing a cover crop that didn't cost anything, because it was volunteer," he says. "The nitrogen was scavenged by the rye and released back to the corn crop."
He notes he did apply 15 gallons of UAN 32% in-furrow with the planter to help meet the early-season nitrogen demand of corn, while his overall use of nitrogen was reduced by 30 pounds per acre.
"With corn, rye is going to tie nitrogen up for a while. That's not ideal, but it takes baby steps to enhance the soil microbes' ability to perform their task of decomposition and mineralization, therefore feeding crop roots," he adds. "Changing the biology of the soil to work better takes time."
Work in progress
Typically, the one-pass approach is restricted to soybeans planted into cereal rye. Rye is typically terminated with herbicide before planting corn, to prevent it from tying up nitrogen that would otherwise be used by the corn crop.
However, Lyle is participating a project to plant corn into standing legume cover crops on a plot on his farm, and he hopes this may lead to more one-pass opportunities in corn. The project, which is funded by an Natural Resources Conservation Service Conservation Innovation Grant, is in partnership with Iowa State University, the University of Wisconsin-Madison and Rodale Institute.
"The one-pass approach has really been a soybean approach. On the Iowa State corn plot, we're using a one pass approach," he says. "On that plot, we rolled hairy vetch this year and planted corn. Then, we don't need nitrogen, because hairy vetch has fixated all the nitrogen we need from the atmosphere.
“The potential is there for one-pass in corn. That potential lies in growing legume cover crops. We know there are challenges with growing rye before corn. If we're serious about mitigating climate change through our farming practices and maximizing our true return on investment, then we need to roll down legume crops before corn."