Herbicide-resistant giant ragweed is destroying crops across the Corn Belt. These farms have found a sustainable solution.
Herbicide-resistant giant ragweed is destroying crops across the Corn Belt. These farms have found a sustainable solution.
August 10, 2021
In 2016, Tom and Irene Frantzen were in the midst of a multi-year struggle with what they call an “evolutionary monster.” Giant ragweed, which can grow to be taller than most people, was sucking up nutrients from the soil and casting shade on the crops they grow on their 320-acre farm in northeastern Iowa.
The Frantzens take a diverse approach to crops and livestock production that’s rare in a region dominated by monocrops of soy and corn. And since the farm is organic, they rely heavily on a five-year rotation of small grains, forages for haying and grazing, and row crops to naturally build fertility and fight pests.
Because of its ability to get a jump-start on the growing season, giant ragweed hammered the Frantzens’ soybeans, cutting yields in half in some cases. But it was the oats that really suffered, which meant the farm was losing a key rotational partner in the form of a small grain crop, impacting everything from the establishment of forage to the fertility of the soil. In short, it threatened the farm’s very viability.
“It was getting worse every year,” recalls Tom, who has been farming since 1974 and whose operation has been certified organic since 2000. “I honestly think people across the road were saying, ‘Frantzen’s a good organic farmer, but he’s finally met his match.’ I felt that was absolutely true.”
Frantzen was recalling his family’s rumble with ragweed on a monochromatic day in early March as he guided his pickup toward a bright green stand of hybrid rye emerging in a 16-acre field. He had planted it the previous fall and was looking forward to harvesting the grain and straw in July, followed by a seeding of a nitrogen-fixing cover crop like peas, which provide grazing forage for the Frantzens’ cattle while building the field’s fertility for future crops such as corn and soybeans. But what the farmer was even more delighted by was what was not there. Five years after the Frantzens planted their first experimental plot of hybrid rye, ragweed’s reign on his farm appears to be over.
Over the past two decades, most farmers have been fighting plant pests like ragweed with the herbicide glyphosate (the chief ingredient in Roundup). As the weeds develop resistance to glyphosate, chemical companies have offered up a series of new products combining multiple older, more toxic herbicides such as 2,4-D and dicamba (along with the genetically engineered crops that resist them) in hopes of fending off this inevitable pest evolution.
So, the fact that the Frantzens and other farmers like them have had success fighting off a mega-weed without herbicides could have larger ramifications for the long-term viability of Corn Belt agriculture, which is suffering agronomically and ecologically from a lack of plant diversity. But can a single crop cure Midwestern agriculture’s biodiversity problem all by itself? No, says Matt Liebman, an agronomist and the H.A. Wallace Chair for Sustainable Agriculture at Iowa State University. After all, a fixation on the silver bullet approach is likely what caused the problem with ragweed in the first place. But Liebman says it provides an opportunity to apply a different, holistic strategy to addressing agriculture’s problems.
“This problem with giant ragweed lends itself to a kind of an ecological modeling approach,” he says. “What if, instead of just using a different herbicide in the same duoculture of corn and soybeans, we looked at changing the crop rotation, what would that do?”
Giant ragweed is the perfect pest: in addition to evolving a resistance to herbicides, it emerges from soil depths of up to four inches, and it has a large seed packed with energy, allowing it to sprout earlier in the spring than most other plants. It also loves high humidity and extreme heat—two weather extremes that are expected to become more common as the climate crises worsens. Weed evolution thrives in a simple farmscape, and it doesn’t get much simpler than the corn-soybean rotation that dominates the Midwest. So, it’s no wonder that giant ragweed is now one of the biggest pest challenges faced by Corn Belt farmers—organic as well as conventional. Liebman says fighting such a superweed requires an ecological approach—utilizing a crop that doesn’t fit into the typical plant-in-spring, harvest-in-fall cycle.
That’s why the Frantzens were so excited when, in 2016, they received a call from the group Practical Farmers of Iowa (PFI) asking if they were interested in experimenting with a new hybrid rye that was being introduced into this country by KWS, a German seed company. Hybrid rye is a “winter annual”—a crop planted in the fall that stays alive through the winter and then is harvested the following summer for grain and straw. Hybridization has revolutionized corn production, but it’s extremely rare in small grains. If most Midwestern farmers are aware of rye, it’s probably as an open-pollinated, unimproved cover crop that keeps the soil covered in the cool months and is good for grazing but has little market value otherwise.
With Midwestern crop production so dominated by corn and soybeans to the exclusion of practically everything else, there is little incentive for the rest of the infrastructure to diversify. Everything from transportation, storage, and processing to marketing, livestock production, and research is constructed around these two crops.
In that environment, there’s little economic incentive or public support for developing a hybridized small grain in the test plots of universities and seed companies, says Liebman. But in many parts of Europe, small grains have remained a key part of cropping systems and livestock diets. The first varieties of hybrid rye were made available there in the late 1980s and Claus Nymand, a KWS product manager, estimates that 20 million acres of the crop are now grown from Russia to Ireland, and from Scandinavia in the north to Spain in the south.
As it did with corn, hybrid vigor in rye has paid off. For one thing, grain yields of hybrid rye can be as much as double that of its unimproved, open-pollinated counterpart. Just as importantly, the new varieties are resistant to ergot, a fungus that resembles rat droppings and is toxic for humans and animals; there’s evidence the Salem Witch Trials hysteria was the result of ergot-contaminated bread.
Liebman says such a winter annual is a perfect way to disrupt weed ecology. Since it’s harvested for its grain and not terminated early in the season like a cover crop, hybrid rye stays on the land until July or August, providing a thick cover and living roots in the soil for much of the growing season. Cover crops help make simple cropping systems more sustainable, but they aren’t a true third crop; it’s the difference between being a rotational partner and a rotational participant.
Hybrid rye has become the latter on the Frantzen farm. In July, they harvested their fifth crop of the grain, which they feed to their hogs (PFI trials conducted on the farm show the processed grain competes well with corn as a swine feed) and have sold it to a specialty miller. They also use the rye straw as hog bedding.
Over the past five years, a few other U.S. farmers have begun raising hybrid rye to break up weed cycles and diversify their portfolio. KWS’s Nymand estimates that as of 2021, 40,000 acres of the grain were grown in the U.S., a tiny fraction of the roughly 180 million acres of corn and soybeans planted this year. Planting hybrid rye is a significant investment—at a little less than $58, the per-acre cost of seeding can be almost double that of its open-pollinated counterpart, although that may seem like a bargain when one considers that herbicide resistance has bumped pesticide costs into the $70 per-acre range for many farmers. Most producers growing it in the U.S. have contracts with specialty millers or whiskey distilleries.
One of those farmers is Richard Magnusson, who farms 11,000 acres with two nephews in northwestern Minnesota. He experimented with 60 acres of hybrid rye in 2016 and this year, he’s set to harvest over 900 acres. He was the first to plant it in his area; now a dozen farmers in surrounding counties raise a total of around 5,000 acres of the crop.
“At times, it’s one of our best crops,” says Magnusson. He likes that it is winter hardy and requires few chemical inputs. At first, he had to haul his harvest several hours to the Twin Cities. Now, with more acres in the area, a local grain elevator has begun shipping it by rail. He’s lucky: many Midwestern elevators are not set up to handle anything other than corn and soybeans. The per bushel market price has ranged from $4 to $8, and Magnusson says he turns a profit when yields top 100 bushels per acre; he’s exceeded that by 40 bushels in spots.
Becca Brattain, the country manager for KWS, says the crop has a wide geographic range, doing well in Canada and from coast-to-coast in the U.S., but yields drop off significantly when it’s planted as far south as Kentucky and Tennessee. An expansive growing range could be good for the environment over a significant part of the Corn Belt. Long-term research out of Iowa shows that diverse rotations that include small grains can significantly reduce erosion as well as fertilizer pollution, while cutting fossil fuel usage.
Iowa State research shows that adding a third crop like a small grain to the corn-soybean rotation can cut greenhouse gas emissions by 54 percent; a fourth crop in the rotation lowers emissions by another 10 percent. A research model developed by Wageningen University in the Netherlands showed that hybrid rye’s carbon footprint is about a third that of corn.
Hybrid rye grows well in the Corn Belt, has multiple uses, and has a lower carbon footprint. Does that mean it’s ripe for a major breakthrough in American agriculture? Not exactly. On the one hand, Albert Lea Seed, a Minnesota company that was one of the first to sell hybrid rye seed in this country, has seen demand increase every year. “In my 30 years in this business, I think it’s the most exciting thing we’ve ever launched,” says company owner Mac Ehrhardt.
However, Ehrhardt estimates that the U.S. is already raising about 90 percent of the rye needed for milling and distilling, meaning that the hybrid version faces the same chicken and egg dilemma other new crops do.
“Production and use have to kinda balance each other out. You can’t just produce a whole bunch and hope it sells,” says farmer Richard Magnusson.
Hybrid rye’s road to mainstream success may actually run through the barn. University of Minnesota Extension crops educator Jared Goplen has crunched the numbers for corn-soybean farmers looking to diversify. “There are ways to make small grains like hybrid rye pay, but it’s going to take livestock as part of the system,” he says.
Around 70 percent of European hybrid rye is fed to livestock, mostly hogs. U.S. feed trials reinforce what the Frantzens have discovered: it can work as a good replacement for soy and corn-based rations. A handful of farmers in Iowa, Minnesota, South Dakota, and Canada are feeding hybrid rye to conventional and organic livestock. Goplen says even CAFOs are showing interest in raising it as feed—since it is harvested in the summer, it provides a window for liquid manure applications on crop fields that would usually be covered in row crops during the growing season.
However, one barrier to making crops that aren’t corn or soy a consistent reality on farms is lack of support for not only developing and adapting local varieties, but helping farmers establish them. In Europe, hybrid rye was developed by university researchers working with KWS. Tom Frantzen is thrilled that he has a new rotational crop, but concerned that it’s not based on homegrown science. “Why isn’t this work being done in the Midwest?” he asks.
The majority of farmers taking part in the 2017 Iowa Farm and Rural Life Poll agreed that small grains were good for soil health and helped break up pest cycles, but just 28 percent felt that such rotations could be as profitable as the corn-soybean duoculture. Lack of consistent small grains markets was a major reason for their concerns, and half of the respondents said the “culture of Iowa agriculture” is not supportive of stepping out of the corn-soybean lane. After all, Iowa, once the nation’s leader in oats production, saw a 99 percent drop in acres planted to the crop between 1950 and 2020. “Culture” can include what kind of science there is to back diversification. Two-thirds of respondents rated lack of technical support and small grains varieties with “elite” genetics as major impediments.
“In Iowa, we haven’t had a small grains breeder for 14 years,” says Iowa State’s Liebman. “It’s a self-fulfilling prophecy—we can’t diversify rotations because we don’t provide what farmers need when it comes to elite genetics.”
It’s not just an Iowa problem: throughout the U.S., the kind of public plant breeding that can provide support for diverse crop rotations is in a “crisis,” funding-wise, according to numerous studies.
Back on his farm, Tom Frantzen says making hybrid rye a player in mainstream agriculture will mean reaching not only conventional farmers, but policymakers and members of the public who would like to see their tax dollars supporting landscape diversity. That will require operating on many fronts: locally, regionally, nationally. As he drove his pickup near the town of Alta Vista in early March, he pointed out a local success: thanks in part to Frantzen’s prompting, the fields on several small Mennonite dairy farms were sprouting hybrid rye.
On a broader scale, he recently worked with fellow Iowa organic farmer Ron Rosmann to pen a letter to Secretary of Agriculture Tom Vilsack inviting him out to see hybrid rye in action and to hear about what the agency can do to promote diversification. The farmer wants to make it clear that this is not just about hybrid rye, or any one crop, for that matter. This is about accepting the reality that agriculture must evolve to stay viable. After all, for years the Frantzens thought their previous five-year rotation was the ultimate answer—evolutionary biology said otherwise.
“The idea to change the corn-soybean monoculture is not to be taken lightly,” wrote Frantzen and Rosmann in their letter to Vilsack. “But, neither can the consequences of the current dominant cropping system.”
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