Can cover crops clean up the Corn Belt?

Laurel Delaware - Soil health field day featuring cover crops and air seeding cover crop into corn

Edwin Remsberg / USDA-SARE

Laurel Delaware - Soil health field day featuring cover crops and air seeding cover crop into corn

Edwin Remsberg / USDA-SARE

Iowa's got a water quality problem, and cover crops could help. But it will mean convincing 50,000 corn and soy farmers to diversify their fields.

To understand Iowa’s water problem, just follow the Raccoon River as it connects the country to the city, flowing south and east towards Des Moines. For more than a hundred years, Iowa’s state capital has relied on the Raccoon for its drinking water. But before it gets there, the river’s three tributaries first travel through some of the most productive farmland in the United States.

This is Iowa, after all, a state that is 85 percent farmland, punching far outside its weight class in terms of agricultural output. Only the 26th largest state by size, Iowa is the country’s second biggest producer of soybeans and its top producer of corn. Given current practices, it’s inevitable that the chemical inputs applied to nearby crop fields are going to end up in the Raccoon River, headed for Des Moines.

The Raccoon and Des Moines rivers join east of Des Moines, Iowa USDA / Flickr

The Raccoon and Des Moines rivers join on the east side of Des Moines, Iowa

In 2013, Bill Stowe, the CEO of Des Moines Water Works, sued the neighboring counties of Buena Vista, Calhoun, and Sac for making his life difficult. As executive of Des Moines’ water utility, it’s Stowe’s job to make sure that the city’s drinking water is safe to drink—no small task, considering the volume of nitrate fertilizer flowing from nearby fields into the river. Nitrates can make tap water unsafe, increasing likelihood of miscarriage in pregnant women and causing a condition called “blue baby syndrome” in infants; high nitrate levels can keep a baby’s blood from oxygenating properly, sometimes resulting in suffocation and death. The Clean Water Act stipulates that the nitrate level of drinking water cannot exceed 10 mg/L. In early summer, after farmers all over the state fertilize their crops, nitrate levels routinely reach 12 to 15 mg/L in the Raccoon River.

In 2015, Stowe told the Des Moines Register that he spent $1.5 million sucking nitrates out of the water at treatment plants outside the city. He estimates that to solve the problem permanently would cost $80 million, and he thinks the nearby counties should shoulder some of the financial burden. But earlier this year, a judge threw out his lawsuit, arguing that the dispute should be resolved by the state legislature, which could regulate farm runoff. That may not happen. Despite clear support among Iowans for improving water quality, the Iowa legislature has dragged its feet on this issue for years.

Still, the specter of regulation, mounting public pressure, and worsening water quality have been enough to get some farmers to agree it’s time to make a change. In fact, there’s already a pretty good solution on the table—one that doesn’t place limits on the amount farmers grow or the volume of fertilizer they use. The trouble is that the remedy requires farmers to plant more, not less, diversifying their fields in a land where corn is king and soybeans are queen.

Air seeder plants cover crops in a cornfield

Signs of hope

Matt Liebman, a professor of agronomy at Iowa State university, studies the economic and ecological benefits of more diversified fields. For over a decade, one focus of his research has been comparing the standard corn-soy rotation—where corn is planted one year, then soybeans the next—to longer, more diverse rotations in which small grain crops (like oats) and hay crops (like red clover or alfalfa) are planted between seasons of corn and soybeans.

Liebman’s rotation trial gained national media attention a few years ago when the published results showed both yields and profits were equal or higher for the longer rotations compared to the standard corn-soybean rotation, with a much lower environmental impact. Weed control was similar across all systems, while “freshwater toxicity”—the system’s potential to pollute adjacent water resources—was two orders of magnitude lower with the more diverse rotations.

Cover crops offer a relatively straightforward, low-cost way to achieve an array of agronomic benefits.

Case closed, you might think. Farmers all over the Midwest must be running out the door to plant small grains and legumes in between their corn and soybean crops.

But when I reach Liebman by phone in his office in Ames he sounds discouraged—and it’s easy to understand why. In many ways these feel like grim times for natural resource conservation in Iowa. It’s not just the dismissal of the Des Moines Water Works suit. Now a state budget shortfall—linked to low commodity prices—makes funding for environmental measures even less likely. In April, the Iowa House and Senate voted to eliminate all funding for the Leopold Center for Sustainable Agriculture, an internationally renowned research and education effort established at Iowa State in 1987. In short, Liebman summarizes, “We are going to be dealing with water quality issues in Iowa for awhile.”

At the same time, there may be signs of hope. Take an issue central to Liebman’s research: the use of cover crops—usually a small grain or legume, like those used in Liebman’s trial—to cover and protect the soil through the winter. Using cover crops isn’t the same as introducing a longer rotation, but it’s a big step in the right direction, helping to prevent soil erosion and keep nutrients out of waterways. The number of farmers using cover crops in Iowa is small—accounting for just 2.6 percent of corn and soybean acres, according to a newly released study—but it’s increased significantly in the past few years.

Soybeans and Cereal Rye Cover CropCarlyn Iverson and USDA-SARE

Planting cover crops like cereal rye in between seasons helps reduce fertilizer runoff and improve soil health

That’s because cover crops offer a relatively straightforward, low-cost way to achieve an array of agronomic benefits. According to Rob Myers, an agronomist at the University of Missouri and regional director of the USDA Sustainable Agriculture Research and Education program, cover crops “are like a Swiss Army knife in the variety of purposes they can serve.” They soak up and hold nutrients at the end of the season, inhibit soil loss to water and wind erosion, and feed soil organisms when nothing else is in the field. In the case of legumes, they can supply nitrogen to the subsequent crop. They build soil organic matter, making soils more resistant to drought. And they can be part of a diversified weed-management strategy in a context of mounting concerns about herbicide-resistant weeds.

Now, some influential people—including Iowa Secretary of Agriculture Bill Northey—are looking for ways to make cover crops a standard practice across the Corn Belt, tight budget picture or no. When newly confirmed Ag Secretary Sonny Perdue toured Iowa last week, he held up a “Don’t Farm Naked” shirt for the cameras—a slogan popularized by the Practical Farmers of Iowa to promote cover cropping. It’s a sign that the practice is gaining traction at the highest levels of the federal government.

“We are talking about a potential for 15 to 17 million acres of cover crops in Iowa,” says Ray Gaesser, a farmer in southwest Iowa who is working on the idea with Secretary Northey. Gaesser is what you call a farm leader—a former president of both the Iowa Soybean Association and the American Soybean Association, a winner of Wallaces Farmer magazine’s “Iowa Master Farmer” award. Gaesser and his family grow corn and soybeans on 6,000 acres, and they sowed 3,100 of those acres to cover crops last fall. He estimates that about 10 percent of the farmers in his neighborhood use cover crops, fewer on a big scale like he does. “But interest is definitely growing,” he says. “There are lots of articles, lots of field days at planting and terminating time. It’s building momentum.”

Secretary of Agriculture Sonny Perdue holds up a “Don’t Farm Naked” t-shirt in Nevada, Iowa

Myers confirms that commodity crop farmers across the Corn Belt and beyond are increasingly interested in cover crops. The USDA Census of Agriculture included numbers on cover crop acreage for the first time in 2012 (a sign in itself of their emerging importance). The US total for cover crop plantings that year was 10.3 million acres; Myers thinks the 2017 Ag Census could show US cover crop plantings approaching the 20 million-acre mark. Myers’s office has been coordinating an annual cover crop survey since 2012, which has turned up some interesting details, including the fact that average cover crop acreage per respondent has more than doubled over the survey period, suggesting that once farmers try cover crops they are pleased with the results and plant more.

For Myers, the uptick in cover crop adoption reflects a new interest in soil health among conventional commodity crop farmers. You can see signs of this browsing conventional farming publications like Successful Farming or Corn and Soybean Digest, which now regularly include articles on cover crop management and other soil health topics. Myers points out that the Commodity Classic, the premier annual gathering for conventional corn, soybean, and cotton growers, has included cover crops among its headline educational themes for the past three years in a row. “Ten years ago they weren’t even talking about them,” he notes.

Despite this momentum, Iowa has only 600,000 acres planted with cover crops today. Will it really be possible to plant 15 million acres every winter across Iowa?

Farm country in northeast Iowa from 10,000 feetUSDA / Flickr

Farm country in northeast Iowa from 10,000 feet

The road to 15 million acres

For starters, it helps to know where the 15 million number comes from. A key player in Iowa’s water quality discussion is the Iowa Nutrient Reduction Strategy, a framework document first published in 2012 and updated regularly as new data become available. The INRS was developed by scientists and managers at the Iowa Department of Agriculture and Land Stewardship, the Iowa Department of Natural Resources, and Iowa State University in response to a request from the EPA’s Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, also known as the Hypoxia Task Force. In its 2008 Action Plan, the Task Force asked each of the twelve states along the Mississippi River to outline how they would meet a 45 percent reduction target for nitrogen and phosphorous loss into the Mississippi River watershed.

Meeting the 45 percent reduction target is voluntary, although under the Obama administration there was an assumption that the request could turn into a requirement if it wasn’t taken seriously. With President Trump in office, that assumption has been turned on its head, but Iowa politicians (many of whom are farmers) have always preferred to emphasize voluntary compliance in any case. “If we don’t do something on our own we’re going to be faced with regulations,” Tim Smith, a corn and soybean farmer from Eagle Grove, told Politico last year, in article that highlighted the local preference for self-policing.

“Fifteen million acres of cover crops means something like 50,000 farmers planting cover crops.”

You could say that now is an excellent time to test the potential of the voluntary approach.

In Iowa, the vast majority of nutrient loss into waterways comes from agriculture. The INRS had teams of scientists working on the nitrogen question and on the phosphorous question; they assembled tables showing the reductions achievable through the use of different practices—for example, by applying nitrogen fertilizer in the spring instead of in the fall, or by shifting to longer rotations—as well what implementing those various practices would cost. Finally, they came up with a list of eight scenarios showing how the 45 percent reduction could be achieved through different combinations of practices, and what those combinations would cost.

Two scenarios rose to the top as meeting both the nitrogen and phosphorous targets for a relatively reasonable price tag. Both rely heavily on the use of cover crops, in part because cover crops are among the few proposed practices that reduce both nitrogen and phosphorous loss. One scenario proposes 60 percent cover crop adoption, the other 95 percent. With around 23 million acres planted to corn or soybeans in Iowa each year, 15 million acres in cover crops would amount to about a 65 percent adoption rate.

Achieving those numbers would be no mean feat, to be sure. At the farm level, introducing a cover crop into a corn-soybean rotation is challenging because harvest for these crops is so late—October or even running to November—leaving little time to get a cover crop established. Most farmers in Iowa use cereal rye, which germinates well even in cold temperatures. The best method is to drill or broadcast the cover crop seed immediately after combining; some farmers hire a pilot to drop the seed by plane into the standing crop earlier in the year. Killing or incorporating the cover crop in the spring prior to planting also requires management decisions: some farmers use herbicides; others use tillage or crimper-rollers; for those with livestock, the spring cover crop growth can also be used as forage.

In Elizabethtown, PA Jim Hershey of Hershey Farms squats in a cornfield. The spring's corn crop can be seen emerging through the winter's cover crop residueEdwin Remsberg / USDA-SARE

In Elizabethtown, PA Jim Hershey of Hershey Farms squats in a cornfield. The spring’s corn crop can be seen emerging through the winter’s cover crop residue

Sarah Carlson, Midwest Cover Crop Director for the non-profit sustainable agriculture group Practical Farmers of Iowa, has been working on these kinds of technical questions with farmers across the state for the past nine years, creating detailed information resources on cover crop species selection, planting dates, seed suppliers, and more. Her work and the work of PFI more generally has been instrumental in facilitating the growth in cover crop use that has taken place so far. So has a small amount of conservation funding at both the national and state levels, for instance to help farmers pay for cover crop planting when they first try it out.

But everyone recognizes that there will never be public money to pay the entire cost of reaching 15 million acres of cover crops in Iowa, much less for funding full implementation of the INRS, estimated at about $4 billion. Acknowledging this reality, a group called the Iowa Agriculture Water Alliance, backed by three of Iowa’s core commodity groups—the Iowa Soybean Association, the Iowa Corn Growers Association, and the Iowa Pork Producers Association—has been focusing on economic development arguments for pursuing the clean-water strategy. Last year, Secretary Northey got behind this effort, announcing a new “Conservation Infrastructure” initiative intended to identify the business opportunities and infrastructure requirements necessary to make the INRS succeed.

Northey recruited Gaesser as his co-chair for the initiative, and Carlson as his cover crop expert. Carlson summarizes their discussions: “We are asking, ‘What are the gaps to scaling conservation in Iowa?’ The first step is to identify those gaps; the second step is to address them. What’s needed to meet the nutrient reduction guidelines? What do we need out there in the landscape?” Taking cover crops as an example, she does the math: “There are about 88,000 farmers in Iowa. Fifteen million acres of cover crops means something like 50,000 farmers planting cover crops.” Among other things, “That means 400,000 acres of [cover crop seed] production. Those are economic opportunities” for farmers, for seed dealers, for co-ops, for equipment manufacturers. Already, a few young farmers have launched businesses providing custom cover crop services.

“We are asking, ‘What are the gaps to scaling conservation in Iowa?’”

“We need to get creative,” Carlson emphasizes. “There’s money to made by being green in the winter in Iowa.”

The group’s argument is backed up by research at Iowa State University’s Center for Agricultural and Rural Development, which has estimated that 2,801 direct and indirect full-time jobs would be created by implementing the INRS scenario involving 60 percent cover crop adoption.

A test plot of crimson clover at USDA NRCS Plant Material CenterEdwin Remsberg / USDA-SARE

A test plot of crimson clover at USDA NRCS Plant Material Center

Carlson has also spent time thinking about how consumers could get involved in bringing about these kinds of changes in the Iowa landscape—for instance, through the creation of a “rotationally raised” label for corn and soybeans, so purchasers could know they were buying corn and soybeans grown with cover crops, or in longer rotations like those modeled in Liebman’s study. The metrics to document these kinds of labels already exist, Carlson notes, in the form of projects like the Field Print Calculator, developed by Field to Market, or the Cool Farm Tool, a greenhouse gas and biodiversity calculator developed by the Cool Farm Alliance. Both of these are industry initiatives, with limited consumer recognition or market return to farmers, at least for now. Carlson would like to see such projects go further, both in encouraging farmers to adopt more sustainable practices and in passing on to farmers the added value such labels could create. Alternatively, she’d like to see farmers themselves organize to define and create a market for “rotationally raised” corn and soybeans.

These kinds of ideas point to a final benefit of making winter cover crops a standard practice in Iowa, which is that they can act as a driver for stimulating adoption of three- or four-crop rotations on at least a portion of Iowa’s corn and soybean land, with the potential to generate additional economic and environmental benefits. Take the case of oats: Iowa used to grow a lot of oats—872,000 acres as recently as 1978, according to USDA data—which is one reason there are still major oat processing facilities in Iowa. Today, those mills process oats grown in Canada or the Ukraine, and when Iowa farmers try to grow oats they sometimes have trouble finding a buyer. Since any of the small grains—rye, barley, oats, triticale—can be grown as cover crops, and since they can all be transformed into a variety of food and feedstuffs for both animals and people, growing lots of cover crops has the potential to stimulate a whole range of market opportunities for agricultural diversification in the Midwest.

Diversification like that might lie far in the future; for the moment, farmers like Ray Gaesser are focused on corn and soybeans. But making corn and soybeans compatible with clean water is starting to sound like an idea most Iowans can get behind.

Correction: An earlier version of this story misstated the year the results of Matt Liebman’s crop rotation trial were published. 

Laura Sayre is a freelance writer and native Iowan currently based in Massachusetts. She has previously written for and Edible Jersey, among other publications; and she is the co-editor of the book Fields of Learning: The Student Farm Movement in North America.