When herbicide-resistant waterhemp began rewriting the rules of weed control for farmers in Illinois, Frank Rademacher didn’t respond by using more products. Instead, he doubled down on no-till and cover crops, betting that a living carpet of rye and roots could do what herbicides alone no longer could.
Rademacher, who farms with his father in Champaign County, recalls the initial transition was a steep learning curve, complicated by making too many changes at one time.
“When we got into cover crops heavy, that was also basically the same year we switched everything over to no-till, and the same year we switched all of our crops to non-GMO,” he says. “Boy, that was a mistake on a lot of fronts, because your weed populations really shift in the process of switching to no-till, at least initially.”
Despite the early hurdles, cereal rye became the foundation of Rademacher’s weed-control program. On his east-central Illinois fields, drilled cereal rye—planted early at roughly 50 pounds per acre—has provided enough biomass to simplify herbicide programs in his non-GMO soybeans.
“There [have been] a lot of times where we have just done like a one-pass herbicide program, so no post spray, and that was in non-GMO beans, and they were really clean,” Rademacher says.
Match Cover Crop Species to Farm Goals
Hundreds of miles away in Virginia, Paul Davis follows a similar philosophy. No-tilling since 1999 and using covers since 2005, Davis views weed control as inseparable from soil health.
“They do so many things,” says Davis, who farms in New Kent County. “Providing erosion control, providing something growing all winter to scavenge any nutrients... making nitrogen, especially this year for my corn crop.”
While Rademacher leans on cereal rye for soybeans, Davis centers his program on a cereal rye-vetch system ahead of corn. Both farmers aim for enough biomass to smother weeds while keeping the cash crop competitive and thriving.
Managing the Fine Line Between Weed and Crop Control
The balance is delicate, particularly with corn. Rademacher warns: “As it relates to corn, the line between enough biomass to fight weeds all season long, and the line between that and having no crop at all can be a pretty fine line. It’s pretty easy to have really good weed control, but also really good crop control.”
To avoid tying up nitrogen, Rademacher opts to use wheat or barley ahead of corn rather than the more aggressive cereal rye.
Davis manages these tradeoffs by decoupling his grass and legumes in the spring. He kills the cereal rye early with a grass herbicide to prevent the Carbon-to-Nitrogen (C:N) ratio from becoming too high.
“I don’t want the cereal rye to go that long, because once it gets a hollow stem, it takes a lot of bacteria eating nitrogen to break that hollow stem down,” he explains.
By late March, Davis terminates the cereal rye but feeds the vetch, letting it grow until it blooms. By mid-May, the vetch forms a two-foot-tall mat that suppresses weeds and allows him to scale back on products.
“That’s really where I’ve cut my herbicide program back the most, in my corn rotation with the heavy vetch stand,” he says.
The Biomass Trap and Termination Timing
Both farmers emphasize that covers complement, rather than replace, good chemistry on their fields. Rademacher warns that a “middle ground” of biomass can actually be detrimental.
“There is kind of a point where you’ve got enough biomass that inhibits some of your herbicide from hitting the ground—too much residue, but not quite enough to get really good weed control to replace that impact,” he says.
He is also “hyper vigilant” about the weather during termination, noting that nighttime temperatures should be above 50°F to ensure the plants don’t shut down. He also cautions about the spray mix used. He sometimes sees termination failures when farmers add clay-based residuals like atrazine in poor temperature windows.
Davis scales his herbicide use based on biomass volume. “If you’re planting into [6,000 to 8,000 pounds], you definitely can reduce your herbicide program,” he says. However, “If you have a weak stand of rye... don’t plan on cutting your herbicide program back.”
On a related front, Davis and Rademacher have been able to reduce their insecticide use. After noticing spider webs in his fields 12 years ago, Davis stopped using them entirely. “I haven’t used an insecticide since—not on corn, beans, wheat, pumpkins, anything,” he says.
Rademacher reports that beneficial predators on his farm now control pests like slugs. “We’ve got such a huge beneficial population... because we haven’t used insecticides now on anything going on six or seven years,” he says.
Weed Control As Part Of A System
Both farmers say weed control is now the product of a broader system they’ve adopted: no-till, continuous roots, high-residue covers, and a more complex biological community above- and below-ground.
To get started with cover crops, Rademacher tells farmers to begin where he believes there’s room for error: with soybeans. “I would get cover crops to have soybeans figured out,” he says. “Just plant… whatever [your] local NRCS recommendations are for cereal rye rates.”
Davis would start out using covers ahead of corn, using a focused cereal rye–vetch program and learning to time termination for both weed control and nitrogen. He stresses growing enough biomass to matter, killing the cereal rye before it gets too lignified, and then letting vetch build the mat that suppresses weeds and feeds the crop.
His main advice to farmers is to think long-term. “It takes five or six years before you really start seeing the benefits,” he says. “God didn’t make Earth in one day, so don’t expect miracles in one day.”
Davis and Rademacher shared their experiences incorporating the use of cover crops on their farms during an online GROW farmer forum addressing the topic of using cover crop mixes for weed suppression. GROW stands for Getting Rid Of Weeds. The organization is a scientist-led network coordinating research to help farmers across the U.S. fight herbicide-resistance with a greater diversity of weed control strategies to complement chemical use.
