Can Cover Crops Cut Water Pollution in Farm Country?

Can Taller Cover Crops Help Clean the Water in Farm Country?

In Minnesota, a local water quality program might serve as a model for incentivizing the next steps in regenerative farming.

Alan Bedtka was paid to plant sorghum-sudangrass to develop organic matter in his soil and reduce his fertilizer use.

Alan Bedtka in a stand of sorghum-sudangrass, which he was paid to plant to increase organic matter in his soil and reduce his fertilizer use. (Photo courtesy of Alan Bedtka)

Under pewter-colored skies, Alan Bedtka tramps through the snow and past a stand of sorghum-sudangrass, its chest-high stems rattling in the harsh wind. The tall forage stands out in southeastern Minnesota’s corn and soybean fields, which this time of year have been reduced to stubble poking through the snow.

Bedtka is in his mid-30s and working to raising a small cow-calf beef herd profitably. That requires cutting costs and labor, and he’d like to keep input-intensive corn and soy out of the picture if he can. Instead, he wants his cattle to harvest their own feed via managed rotational grazing, even in the winter.

“Any day you can graze is better,” says Bedka.

It turns out a system that relies less on row crops isn’t just good for a time- and resource-strapped young farmer. A snowball’s toss away, a trout stream called Crow Spring snakes through the white landscape. Yet the bucolic scene belies an environmental problem roiling beneath the surface: The groundwater in this part of Minnesota is so contaminated with nitrates running off farm fields that the U.S. Environmental Protection Agency (EPA) has recently called on three state agencies to take action to protect the health of rural residents.

The Minnesota Pollution Control Agency says 70 percent of the state’s nitrate pollution is coming from cropland.

That’s where the sorghum-sudangrass comes in. It works as both a cover crop and forage for the cattle, and it’s helping Bedtka build up organic matter in his soil. He was paid to plant it by the Olmsted County Groundwater Protection and Soil Health Program, a local effort that seeks to reduce overall fertilizer use by building soil—therefore cutting down on the nutrients that enter waterways—while helping farmers save money.

In its inaugural season, the program has already helped keep tens of thousands of pounds of nitrates out of area water. The initiative goes beyond pushing the establishment of an isolated practice to take a holistic, integrative approach. And its early success has conservationists and lawmakers hoping it can become a model for local, state, and federal farm conservation programs, and in the process serve as a way of disrupting the corn-bean-feedlot machine that dominates Midwestern agriculture.

Nipping Nitrates at the Source

In 2022, Olmsted County commissioners Mark Thein and Gregg Wright approached staffers in the local soil and water conservation district office and asked a seemingly straightforward question: How can we keep nitrates out of the groundwater? Thein, whose family runs a well drilling business, is troubled by the increase in contamination he’s seen over the past few decades in the aquifers he taps throughout southeastern Minnesota.

“It’s not in society’s best interest to look the other way,” he says. “I don’t think it’s fair to the next generation.”

Southeastern Minnesota is a hollow land—its geology is characterized by porous limestone that allows contaminants to easily make their way into underground aquifers. Nitrates are a particularly troublesome pollutant, given their ability to escape the surface and seep deeper into the Earth, often in a mysterious and unpredictable manner. High nitrate levels can cause a sometimes-fatal condition called “blue baby syndrome” and has been linked to colorectal cancer, thyroid disease, and neural tube defects.

The EPA has set the drinking water standard for nitrate at 10 milligrams per liter, or 10 parts per million. Recently, research has hinted at serious health problems associated with nitrate levels lower than that. Minnesota Department of Agriculture testing has shown that over 12 percent of the private wells tested in the eight-county karst region of southeastern Minnesota exceeded the EPA’s drinking water standard. More than 9,000 residents in the region have been or still are at risk of consuming water at or above the EPA standard, according to a letter the agency released in November 2023.

A winter view of Alan Bedtka's sorghum-sudangrass cover crops during a soil health field day led by Olmsted SWCD staff. (Photo courtesy of Alan Bedtka)

A winter view of Alan Bedtka’s sorghum-sudangrass cover crops during a soil health field day led by Olmsted SWCD staff. (Photo courtesy of Alan Bedtka)

The Minnesota Pollution Control Agency says 70 percent of the state’s nitrate pollution is coming from cropland. Corn requires lots of nitrogen, and it’s by far the most commonly used fertilizer in the United States. Iowa farmers, for example, apply it on 87 percent of their fields at a rate of 149 pounds per acre. Annual crops take up only about half of the nitrogen applied, and the rest often ends up polluting groundwater in the form of nitrate.

This doesn’t just create problems in local drinking water wells. Nitrogen and phosphorus escaping Midwestern farm fields are the major cause of the hypoxic “dead zone” in the Gulf of Mexico, which is about the size of Yellowstone National Park. The EPA’s latest National Rivers and Streams Assessment found close to half of the country’s waterways were in “poor condition,” and nutrients such as nitrogen are a leading culprit.

Southeastern Minnesota’s Olmsted County is a microcosm of agriculture’s dependence on nitrogen fertilizer. Since the 1940s, oats, wheat, hay, and pasture have been replaced by a duoculture of corn and soybeans. In addition, large concentrated animal feeding operations, which have become more prevalent there in recent years, add to the problem by disposing millions of gallons of nitrogen-rich liquid manure.

Olmsted County officials acknowledge that water in certain areas of the county will continue to see increasing nitrate levels as the contaminant moves deeper into aquifers. And when nitrates are present, it’s inevitable that other contaminants, such as pesticides, are also polluting the water. “We’re allowing this to happen,” says Caitlin Meyer, the water resources coordinator for the Olmsted SWCD. “But what can we do to prevent this in the first place?”

Dialing up Diversity

One standard approach to cleaning the water that runs off farms is planting cover crops. Indeed, studies have shown that when cover crops grow between the corn and soy seasons, they provide the kind of soil environment that builds natural fertility and cuts nitrate leaching by anywhere from 40 to over 70 percent.

Cover cropping has also gained a reputation as a tool for sequestering carbon and thus mitigating climate change. Since 2016, the U.S. Department of Agriculture (USDA) has made available more than $100 million in funds to help farmers establish cover crops.

Despite the resources devoted to advancing the practice, however, only around 5 percent of U.S. farmland is regularly cover cropped. The cost can be prohibitive, and it can be tricky to fit them into a conventional row-cropping system. A 2022 Stanford University satellite study reported that although cover cropping reduces erosion and improves water quality, it also causes significant yield hits for corn and soybeans. And some scientists are concerned that cover cropping’s role in climate change mitigation has been overplayed.

For a time, the Olmsted County SWCD administered a traditional cover-crop program funded by the USDA that helped farmers with establishment costs. Angela White, a soil conservation technician for the SWCD, says the program was valuable in getting cover crops established in the region and showing that it could work, but it had limitations as far as producing environmental benefits. Farmers would often plow the cover under early in the spring before it could provide optimal soil health benefits, and USDA restrictions didn’t allow much flexibility.

Ray Weil, a University of Maryland soil ecologist who has worked with farmers in numerous states, says when farmers are paid to implement an isolated practice such as cover cropping, they can become too focused on the minimum needed to qualify for payments, and they don’t consider the overall soil health picture.

But Weil and other experts also say cover cropping can be a “gateway practice” for implementing the five principles of soil health promoted by the USDA’s Natural Resources Conservation Service or NRCS: armor the soil, minimize disturbance (i.e., reduce tillage), increase plant diversity, keep roots in the soil as long as possible, and integrate livestock.

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Plant diversity and covering the land has long been associated with more resilient soil. But experts say the integration of livestock via rotational grazing can also help reduce reliance on continuous plantings of fertilizer-intensive crops. And that’s where the Olmsted County Groundwater Protection and Soil Health Program enters the picture. The program pays farmers to plant cover crops, but it digs deeper to ensure that they get real results.

Research shows that allowing cover crops to grow to significant heights can dramatically reduce pollution. So, the program pays a farmer $55 an acre to grow their cover crops to at least 12 inches; at 24 inches, they receive an additional $20 per acre. Planting a cash crop within a living stand of cover crops, a technique called “planting green,” garners a farmer an additional $10 an acre. Farmers can also receive payments for growing so-called “alternative” crops such as oats and other small grains, and for converting crop acres to deep-rooted perennial systems like hay and pasture.

Each farm can qualify for a maximum of around $15,000 in payments per year. When Olmsted County SWCD staffers originally brainstormed with area farmers about setting up the soil health initiative, they considered a per-farm cap of $20,000 to $25,000. However, the farmers insisted on a lower cap so that more money could be spread around on more acres.

“I put $6,500 total expenses into seeding—the program paid back $3,500,” says farmer Logan Clark, who used the program to convert cropland to rotationally grazed pasture on his hilly, erosion-prone farm. “So, I’d at least be $3,500 more in the hole if I didn’t have the program.”

SWCD staffers say one advantage of the program is that because funding comes from the county—the commissioners agreed to set aside $5 million in American Rescue Plan Act funds for the program—rather than the USDA, they have more freedom to allow farmers to experiment and learn from their mistakes.

“I know farmers who have been cover cropping or strip tilling for decades … Now they are hungry for what’s next.”

Mark Stokes has been using no-till cropping for 26 years. Around five years ago, he noticed that even on his no-till acres he was seeing erosion, so he started growing cover crops utilizing traditional cost-share programs. He isn’t afraid to experiment—he’s grazed his beef cow herd on a mix of nine cover crops, and a few years ago, after seeing it being done on YouTube, mounted a seeder box on his combine so he can plant cover crops while he’s harvesting corn.

Stokes enrolled in the Olmsted SWCD program in 2023 to help cover the risk of yet another innovative practice. Through the contract, he agreed to plant his corn and soybeans into growing cereal rye green and terminate the rye after it hit 12 inches tall. It turns out the dry conditions made it a bad year to let a cover crop grow tall. On the other hand, the oats he raised in 2023 thrived.

When it came time to sign up for the 2024 round of the program, Stokes took advantage of its flexibility. “I signed up for more oats, so we don’t have to worry about the cereal rye so much, and if we have to, we can terminate it sooner.”

Not all participants in the program are going to check all five soil health principle boxes, but flexibility can serve as a seedbed for aspirational farming. Alan Bedtka wants to follow as many of the principles as possible. In 2023, he used the program’s funds to grow his cover crop to 12 inches. He also signed up to raise cover crops for seed production, which qualified him for the alternative crop portion of the initiative. Finally, his use of rotational grazing and the growing of forages on formerly row-cropped land qualified him for the haying and grazing payment.

“Protecting water quality is a perk, but the main reason I’m doing it is to try to be more profitable,” says Bedtka as he stands in a recently grazed cover-cropped field that he hasn’t had to add fertilizer to for two years. Nearby is an exposed limestone hillside, a reminder of the area’s vulnerable karst. Bedtka explains that his healthier soil absorbs and stores precipitation better. “So that means you’re growing more grass and more cows per acre. All the benefits are kind of tied up into one.”

Like Stokes, Bedtka is now able to take a more integrative, whole-systems approach with less financial risk.

“I know farmers who have been cover cropping or strip tilling for decades . . . Now they are hungry for what’s next,” says Kristi Pursell, who, when she headed up the watershed group Clean River Partners, supported farmers adopting practices to keep ag pollution out of southeastern Minnesota’s Cannon River. “The Olmsted SWCD program respects the knowledge that these farmers have of their land and their previous experience.”

Truckloads of Disruption

Soon after the Olmsted County program was launched as a pilot in 2022, 52 farmers signed up to grow tall cover crops—more than double what was expected. In total, they agreed to grow cover crops up to 12 inches high on over 5,300 acres and 24 inches on 2,700 acres. This year, over 70 farmers have signed up to raise cover crops under the program, representing almost 13,000 acres.

There are 240,000 acres of cropland in the county, so the majority of the area’s farmers aren’t participating in this initiative. But the program may be having an outsized impact on soil health. The SWCD estimates the environmental results of the program by combining the nitrate reduction directly observed on its own research farm with some of the wider research that’s been done. It estimates that in 2023, the program kept roughly 310,000 pounds of nitrates out of the county’s drinking water.

Surveys show that most farmers plant more cover-crop acres than they are getting paid for— something they can afford to do because the SWCD contracts pay so well, says Martin Larsen, a farmer and conservation technician for the district. When the SWCD includes those additional acres, the amount of nitrates being kept out of the water goes up to 560,000 pounds—or the equivalent of 23 semi-truckloads of urea fertilizer.

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“The contracts are generating a nearly two-to-one payback in terms of soil health practices that are put in place on the farms,” says Larsen.

At the SWCD office, Caitlin Meyer, the water resources coordinator, points to a color-coded map that shows where farmers have signed up for the program so far; soil-friendly practices are being used in most areas of the county. “If we could get 30 percent in our subwatersheds put into cover crops, we’d be making real progress,” she says. One estimate is that some watersheds are approaching the 20-percent mark.

Larsen, who got his start using regenerative practices by planting cover crops a few years ago, then displays a chart showing what kind of acreage changes could occur if the program lives up to its potential over the next five years—9 percent less corn, 13 percent fewer soybeans, 417 percent more cover crops, 95 percent more oats, and 5 percent more pasture. If the effort succeeds, in other words, it could significantly disrupt the corn-soybean system in the region.

“For generations we’ve been telling farmers to do exactly what they’re doing. If we want them to change, we need to change.”

It might also serve as a model in other counties in Minnesota and beyond. Dagoberto Driggs, who coordinates the National Healthy Soils Policy Network, says the data from the Olmsted effort’s research farm helps determine an accurate estimate of the program’s benefits, ensuring public resources are being invested wisely. He adds that a program like this fits well with the current push on the part of regenerative agriculture groups across the country to create conservation incentives that are flexible enough to allow farmers to innovate and adapt. Driggs would like to see something like the Olmsted County program tried in other parts of the country.

“We really need a more holistic approach based on the soil health principles, which is what I find striking with this program,” says Driggs.

Mark Thein, the well-driller and county commissioner, hopes a cost-benefit analysis could show that such a proactive program saves taxpayer money by reducing the need for new drinking water infrastructure to deal with pollutants. It would be ideal, he adds, if the state would create a large-scale version of the program, taking pressure off local governments.

The timing could work in his favor. An analysis by the Star Tribune newspaper found that despite the fact that Minnesota has spent hundreds of millions of dollars to reduce nitrate pollution over the past few decades, the problem has not gone away.

When the 2024 session of the Minnesota Legislature convened in February, lawmakers began drafting legislation that would create a pilot nitrate-reduction program modeled after the Olmsted County initiative. Pursell, who is now a state representative, is working on the legislation. She’s frustrated with the lack of progress made to reduce ag pollution and blames federal policy such as the farm bill, which encourages farmers to grow little other than corn and soybeans.

If a local pilot is successful, Pursell says it could help farmers transition out of the corn-soybean duoculture in a financially viable manner—and give taxpayers a return on their investment in the form of clean water, a crucial public good.

“I want to make sure that when we are spending money, it’s for an outcome, and it’s not just to tick a box,” she says. “For generations we’ve been telling farmers to do exactly what they’re doing. If we want them to change, we need to change.”

Brian Devore is the author of Wildly Successful Farming: Sustainability & the New Agricultural Land Ethic (University of Wisconsin Press). He edits the Land Stewardship Project Letter and produces the Ear to the Ground podcast. Read more >

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