- ‘Prosperity,’ customer pressure help stir cover crop interest
- The ‘yo-yo’ principle of managing cover crops
- Is USDA overpromoting cover crops?
This is the first part of a four-part series examining the promise of cover crops, the potential for them to meet the nation’s environmental goals that rest on their success, and the potential pitfalls and unintended consequences of trying to make cover crops work in parts of the country where they currently don’t. Future installments will look at what it takes for cover crops to work financially; the potential for turning cover crops into cash crops; and the impact of policy barriers and incentives on the practice.
A field on Barry and Eli Little’s South Dakota farm is riddled with green one day this fall well after the harvest of their winter wheat crop. The green is the first telltale sign of a complex mixture of plants that are increasingly seen as the key to addressing some of America’s most pressing environmental challenges, from water pollution to climate change.
The tops of purple radish bulbs pop out of the ground, surrounded by the leaves of 14 other plants. Barry Little rattled their names off one by one: cow peas, millet, sun hemp, turnips, flax, sunflowers, oats, buckwheat, African cabbage, crimson clover, sorghum, sudangrass and soybeans. Each species has a distinct function, he says.
The plant mixture is the Littles’ cover crop for this winter, and the benefits include reduced soil erosion and compaction, less runoff of sediments into waterways, improved water infiltration, and fewer weeds, just to name a few.
“Under the soil, there's a lot going on,” Barry Little said.
Eli, his son, jumped in and added, “We even found where we did some of the inter-seeded cover crop on the corn and on hilltops, we had better corn than we've ever seen.”
That promise of improved crop yields, coupled with the potential for reduced inputs and the potential for payments from state and federal governments as well as private companies are fueling increased farmer interest in cover crops in many regions of the country.
Even President Joe Biden, who referred to incentivizing the practice for its climate benefits in his first address before Congress, has his eyes on their potential.
The $2 trillion Build Back Better bill that he’s trying to push through Congress includes more than $27 billion in new conservation funding, which could add rocket fuel to the cover crop movement. The bill includes a new, five-year program that would pay farmers $25 an acre for planting up to 1,000 acres of cover crops.
Cover crops could also provide farmers with new revenue streams. Some farmers already are cutting them for hay and allowing them to be grazed. Others are starting to earn credits through fledgling carbon markets. The U.S. airline industry is looking at oilseed cover crops as a potential feedstock for the biofuel needed to reduce the carbon footprint of jets.
But cover crops may not work well everywhere, and some farmers are warning about the unintended consequences that could occur if the federal government and private industry go too far in promoting the practice.
In water-strapped areas of the central and southern Plains and western regions of the United States, cover crops can pose a challenge for farmers like Dan Atkisson, who gets around 20 to 22 inches of rainfall each year on his cattle, wheat, sorghum and corn operation in northwest Kansas. He said many producers who raise sorghum in dry climates feel the same way.
“Moisture is going to be our limiting factor to what we can produce, and hence, our profitability,” Atkisson told Agri-Pulse. “So, we don't want to see any kind of a mandated-type cover crop in a system, because they just don't necessarily work in every geography.”
Sorghum and wheat growers are also concerned that incentives for cover cropping systems, which may work well for corn and soybean growers in the Midwest, will simply encourage growers to plant more corn and soybeans in arid regions of the country — thereby reducing plantings of winter wheat and sorghum or incentivizing more irrigation.
A great deal depends on how you would structure a cover crop incentive program, says Clay Pope, a wheat grower and member of the National Association of Wheat Growers who farms near Loyal, Oklahoma. “Every area is going to be different,” he adds. “You've got to have some flexibility and the opportunity to make changes as more information becomes known.”
Cover crop usage spreads, but still concentrated
In every county in the United States where there is a cash crop such as wheat, corn, soybeans, cotton or fruit, nuts and vegetables, at least one farmer is now planting a cover crop, from Delaware to California and even Hawaii, says Rob Myers, the national liaison on cover crops and soil health for the Sustainable Agriculture Research and Education (SARE) program and the director of the University of Missouri’s Center for Regenerative Agriculture.
“The surge in interest really started happening around a decade ago and a lot of that was connected to soil health,” Myers told Agri-Pulse. “As people have learned more about how to manage soil health, the interest in cover crops has really shot upwards.”
In 2017, U.S. farmers planted 15.4 million acres of cover crops, according to a report by the U.S. Department of Agriculture’s Economic Research Service. That’s a 50% increase from 2012, when farmers planted 10.3 million acres.
Producers are asking how cover crops can benefit their yields and overall soil health, and people like Jared Knock, who works in business development for Millborn Seeds, encourage everyone to be thinking about multiple benefits.
In recent years, he’s seen more organizations, both public and private, “who are looking to help farmers voluntarily adopt these practices, which have shared benefits, not only for the farmer but for the rest of the ecosystem.”
“There’s more prosperity in the farm community than we’ve had in a while so people are able to think longer-term, bigger picture, about what my farm might look like in 100 years instead of just trying to make annual payments,” Knock said. “Couple that with the talk about agriculture’s role of decarbonizing the environment and people are seeing that climate-smart agriculture is really conservation agriculture.”
Cover crops are more commonly used in some areas of the U.S. than others. In Maryland, where planting cover crops has been heavily promoted and incentivized by the state government to curb pollution into the Chesapeake Bay, cover crops were grown on 33% of the cropland in 2017, according to USDA. Other northeastern states have also seen high levels of adoption.
But in the Midwest and Great Lakes regions, the practice has grown at more moderate rates, and some states in the West — including Colorado, Washington, Wyoming and New Mexico — have actually seen declines in cover crop adoption.
Many species of plants can and do work for cover cropping, but some of the most common types are grasses, brassicas and legumes — including winter annuals like crimson clover and summer annuals like cowpeas.
Agronomists say producers have to factor in what might grow best with their soils, weather patterns and topography as they look to use cover crops to solve some of the problems they see in their fields.
“The thing is, like much else in ag, there cannot be a cookie-cutter approach,” said Francisco Calderon, the director of the Columbia Basin Agricultural Research Center at Oregon State University.
Management is key to getting the benefits
Lee Briese, a crop consultant in North Dakota, said effectively getting benefits from cover crops takes time, effort, and experimentation. He compares it to learning how to do yo-yo tricks. Nobody can just pick up a yo-yo and know how to do advanced tricks. They have to take the time to learn them, one after another.
“This is a new technique,” Briese said. “This is a new practice for a lot of farms and you actually have to work your way up to it. You have to learn how to get it to work in your system, and everybody's system is a little bit different.”
For a detailed look at cover crop benefits, read: Cover crops can benefit farmers as well as the environment
PepsiCo Inc., one of many food industry giants that are trying to reduce their greenhouse gas emissions by working with farmers to sequester carbon through regenerative agriculture practices, has found that it’s critical to provide growers with knowledgeable advice about cover crops.
The use of cover crops represents “a big change in an operation. You do not want to mess up your cash crop in doing cover crops the wrong way,” said Margaret Henry, PepsiCo’s director of sustainable agriculture.
PepsiCo provides payments directly to farmers and provides technical advice through independent organizations such as Practical Farmers of Iowa and the Illinois Corn Growers Association. Farmers in the program planted 89,000 acres of cover crops in 2020 and the goal was to have 200,000 acres in 2021.
In California, Braga Fresh Family Farms has incorporated Merced rye and a few cover crop mixes into its crop rotation plan for its operation that grows cool-season vegetables.
Eric Morgan, Braga Fresh’s vice president of environmental science resources, said the company aims to help stabilize slopes. He also said cover crops helped to capture residual nitrogen in the winter and convert that nitrogen into plant tissue, which can sometimes be made available for their first or second crop in the spring.
“A crop after a cover crop will have better yield, the soil will be softer,” he said. “Cover crops help us out quite a bit.”
Caleb Akin, who runs A&W farms in Cambridge, Iowa, with Noah Wendt, regularly deals with weeds like water hemp, ragweed, buttonweed, and foxtail — which he emphatically says is “the worst.” But for the farm’s organic, no-till soybean field, he and his partner needed a way to fight weeds without spraying, so they’ve implemented buckwheat between rows.
“Cover crops are the key to it,” Akin said. “Where there could be a weed growing, you're putting a cover crop there instead. So now you're in control of what weeds you're dealing with.”
Briese said that cover crops can provide a lot of solutions to problems that are becoming increasingly harder to solve mechanically, like controlling herbicide-resistant weeds. But he warns farmers that cover crop effectiveness depends on a variety of factors, some of which are out of the producers’ control.
“It's a biological thing, it's not a mechanical thing,” he said. “When we do something mechanically, whether tillage or mowing or whatever, you can force it to happen. When you're talking about biology, you need the environment to work for you.”
But Missouri producer MacCauley Kincaid believes that a shift in mindset from depending on mechanical practices and chemicals to biologically based solutions is important for the long term.
“When you start thinking about your farm as an ecosystem, instead of a chemistry set, then that's when we can really start doing ecological benefits for the environment,” Kincaid said
Good management is critical to sequestering carbon, too
Cover crops add biomass to the soil, which helps to pull more carbon out of the atmosphere and store, or sequester, it in the soil, which can help reduce greenhouse gas emissions. That’s why cover crops are a key part of the Biden administration’s strategy to use agriculture to help cut U.S. emissions in half by 2030.
To keep the carbon from returning to the air, the biomass has to stay in the ground, which is why effective carbon sequestration also requires management practices that don't break up the soil, said Rattan Lal, a renowned soil scientist at The Ohio State University who was awarded the World Food Prize for his research around restoring soil fertility and carbon sequestration.
When plants photosynthesize and take in carbon dioxide, they create biomass, one of the most common forms of soil organic carbon below and above the ground. That biomass returns to the same land where the plants are growing and, over time, gets broken down by soil microbes into humus — a substance similar to compost, but made without oxygen.
“Grow a cover crop,” Lal said. “Suppress it, mow it, but don't plow it. Then, carbon will stay in the soil.”
Jinshi Jian, a former research associate at the Pacific Northwest National Laboratory-University of Maryland Joint Global Change Research Institute, was part of a group of scientists that collected 1,195 soil organic carbon comparisons from 131 different studies and conducted a meta-analysis that looked at soil organic carbon changes after the use of cover crops.
The researchers found that cover cropping caused a 15.5% increase in soil organic carbon in soils at or above 30 centimeters deep, leading them to conclude in the paper that “inclusion of CCs (cover crops) into agricultural rotations can potentially increase soil carbon sequestration.”
“The results clearly show that if we manage our croplands properly, then we can increase the carbon stock,” Jian said.
Additionally, the study found that soils planted with cover crop mixes had larger soil organic matter increases than mono-species cover crops. Legumes and legume mixtures also saw significant soil organic carbon increases, while grass and grass-legume mixtures did not change soil organic matter significantly.
Jian said legumes tend to do better than grasses with storing soil organic carbon because they tend to have more biomass and a low carbon-to-nitrogen ratio.
“Combined, these two tend to have a good feedback to the soil organic carbon,” Jian said.
Soil types also play a role. Fine-textured soils saw a 39.5% mean change in soil organic carbon after cover crops, while coarse-textured and medium-textured soils saw mean changes of 11.4% and 10.3%, respectively.
Too dry? Too cold? Cover crops won’t work for me, some farmers say
Farmers cite several challenges with cover crops. One is the additional time and labor they require; some 38 of 66 cover crop non-users surveyed by SARE and the Soil Health Institute raised that concern.
Planting a cover crop, in addition to a cash crop, creates a new burden for a farmer to bear. In addition to caring for their cash crop, farmers must think about what their cover crop requires, particularly when it comes to seeding and termination. And, since some producers wait until after harvest to seed cover crops, they only have a limited window of time to get that crop planted.
“One reason farmers that have not yet used them often cite as a barrier is they feel they don't have time to get them planted such as in the fall if they're growing summer crops like corn and soybeans,” Myers said. “So they may feel really busy in the fall with harvest and fall fieldwork, and they just don't have time to do a cover crop.”
That planting window can get especially small in the northernmost U.S. states. Briese said in North Dakota, where frosts tend to come at the end of September or sometime in October, it can be difficult to establish a cover crop in the time right after the corn or soybean harvests.
“The recommendation really is if we can get them seeded before the third week in August, we get pretty good cover crop growth,” Briese said. “If we get into September, then it's marginal whether or not you want to do it, just because we don't have enough time for growth.”
Growing cover crops, like all other plants, requires water, which can be another challenge to producers in arid and semiarid regions of the Great Plains and West.
Steven Nielsen, a former USDA Agricultural Research Service scientist, told Agri-Pulse he’s grown frustrated with the Natural Resources Conservation Service for what he deems the “universal promotion” of cover crops, which spurred him to research their applicability in the water-scarce regions of the Central Great Plains.
NRCS "made some incredible claims about them not using water to grow and so that was the impetus of my research, to really determine whether cover crops grown in mixtures didn’t use water, which was just an annoying claim to me, and, I thought, irresponsible to farmers in the Central Great Plains,” Nielsen said.
Through his research, Nielsen said he has found that aside from providing cover and increasing resistance to wind erosion, cover crops “aren’t very useful” in water-limited areas of Kansas, Oklahoma, Colorado and Texas. His studies have tested grasses, oats, some oilseeds and some legumes.
“Cover crops have their potential uses in high precipitation areas or under irrigation,” he said. “They don't really have a valuable use in water-limited situations and in dryland agricultural systems. That's my opinion.”
One report he helped author on the subject states that on dryland operations in semiarid regions, “cover crop water use may result in significant yield loss in following crops such as winter wheat.”
Barry Evans, a cotton grower near Kress, Texas, midway between Lubbock and Amarillo, worries about farmers irrigating their cover crops to get them to grow. He fears that will further deplete the Ogallala Aquifer, the lifeblood of the region’s agriculture.
“I think there can be some negative things in our area about being incentivized to pump water” for cover crops, he said.
Evans, who was recently named farmer of the year by Field to Market, an organization that works with the ag supply chain to facilitate sustainable farming practices, protects his soil’s fertility and moisture with rotations of high-residue crops such as sorghum or wheat and leaving fields fallow.
John Holman, a professor of agronomy at Kansas State University, has also been researching some cover crops like winter triticale, winter wheat, winter lentils, spring oats, spring triticale, spring peas and some mixes to try to figure out how cover crops impact moisture in Kansas soils.
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One of Holman’s findings: The longer a cover crop grows before the next cash crop, the more negative the impact on the cash crop’s yield.
“If you terminated that thing the minute it came out of the ground — right when it emerged — it's not going to use any water, but you're not going to get any benefit either,” he said. “And if you let it grow too long, what we’ve seen is it’s a lot bigger impact on the next crop.”
Farmers face similar concerns in water-stressed Western states.
“Most guys can't put water on a cover crop because it's not returning much economic yield and the water that they have they're trying to save for the crops they're trying to grow,” said Cannon Michael, who grows tomatoes, melons, extra long staple cotton and other crops in California’s Central Valley. “There's some additional challenges, I think, with California.”
Most of the research on cover crops has been done in other regions of the country, so it’s not clear how effectively they can be used in the Central Valley, he said.
“We're just trying to learn and see if it's going to be beneficial and what other practices might make sense,” he said. “We're not against them, but it's just a little bit more complicated out here.”
However, some scientists are trying to find ways to make cover crops work in dryland systems. For example, Oregon State University researchers are testing cover crops on winter wheat cash crops in Morrow County, Oregon, which gets around nine inches of rainfall a year. One of the researchers, Christina Hagerty, said they’re seeing some promise with winter peas, spring barley and a mixture of fall-planted cover crops.
“Those were kind of our standouts in terms of getting nice biomass and that biomass is then what contributes to eventual organic matter, trapping snow, things of that nature,” Hagerty said.
Don Hineman, who farms 10 miles outside of Dighton, Kansas, hasn’t had much success with cover crops. But he has found after the summer wheat harvest, if he leaves the remaining stubble in the soil until the spring, he can get some of the benefits.
“We absolutely see an increase in yields for corn and milo (grain sorghum) when we plant into standing wheat stubble,” he told Agri-Pulse.
Other regions of the U.S. have problems with excess water, an entirely different challenge for cover crops. One of those is the Delmarva Peninsula, the flat region sandwiched between the Atlantic Ocean and the Chesapeake Bay that has poorly drained soils.
Managed properly, cover crops can actually help soak up some of the excess moisture, said Ray Weil, a professor of soil science at the University of Maryland.
“Even when your water's a problem, it's less of a problem with the cover crops, especially if you learn to plant green,” he said, referring to seeding the cover crop before the cash crop is harvested.
Jay Baxter, who farms near Georgetown, Delaware, half an hour from the Atlantic Ocean shoreline, says one low spot in his field that sees continued soil compaction can become a “puddle” after filling with water. However, cover crops have helped him get rid of some of that excess water by increasing infiltration.
“As long as we can keep from having 6-, 8-, 10-inch rain, we generally can shrink that puddle,” he said. “We’ve seen year in and year out that we’ve been able to average things out a lot easier.”
“We can still do it (cover crops). We can still get away with it. But it's proper drainage. As flat as we are, you need the drainage,” said Doyle, who is vice president of the American Soybean Association.
It’s taken time, but SD farmers sold on cover crops benefits
When the Littles started planting cover crops on their South Dakota farm in 2014, their main goal was to get another feed source for their cattle. But the possibility of having living roots in the soil throughout the winter became more important as the Littles learned about — and saw — the soil health benefits.
"There's people who think that planting cover crops is our goal,” Barry Little said. "But cover crops are just a tool to fix our soil."
The turnips, radishes and sunflowers break up soil compaction. The millet scavenges nitrogen. The sorghum sudangrass has become a nutritious source of feed for their cattle. The remaining species contribute in some way to the overall health of their soil.
"It seems to work,” he said.
Cover crops can benefit farmers, earth in many ways
The Midwest Cover Crops Council, the Northeast Cover Crops Council and the Southern Cover Crops Council have created tools to help producers in their regions decide on the right cover crops based on their goals, soil types, growing season lengths and locations.
USDA-funded Sustainable Agriculture Research and Education program and other experts say that if used correctly, cover crops can provide the following benefits in certain conditions:
- Carbon sequestration: Farmers who use the right cover crops in conjunction with a no-till system can trap an extra 750 to 800 pounds of carbon per acre per year in the soil, says Rattan Lal, a soil scientist at The Ohio State University. Similarly, a study analyzing data from 131 different studies found that cover cropping increased soil carbon by 15.5% near the surface. Lal cautions that the soil must be left unplowed to retain the carbon. Biomass also could be lost through haying and grazing, he says. Carbon sequestration rates depend on temperature, latitude, soil texture and other environmental and management factors.
- Reduced fertilizer costs: Cover crops such as hairy vetch, medium red clover, Austrian winter peas and fibrous-rooted cereal grains can contribute nitrogen to the following cash crops. Reducing nitrogen usage, in turn, can reduce emissions of nitrous oxide from fields, the largest source of greenhouse gas emissions from U.S. agriculture.
- Reduce soil erosion: With enough stalk and leaf growth, many cover crops can help prevent soil loss, particularly in winter months when nothing else will grow in fields.
- Suppress weeds: Cover crops use water and nutrients and block light that is needed by weeds. Cover crops also change the soil surface temperature or possess herbicidal compounds in their roots that can effectively prevent weeds. Cereal rye, barley, oats and mixtures can be effective for keeping weeds at bay, SARE says.
- Improve soil health and nutrient cycling: According to SARE, there are several ways that cover crops can improve soil health. For example, rye can add organic matter to the soil, sorghum sudangrass has deep roots that can help relieve soil compaction and ryegrass can “stabilize field roads, inter-row areas and borders when soil is wet.”
- Conserve soil moisture: Cover crops can help increase water infiltration and reduce evaporation. Rye, wheat and sorghum-sudangrass hybrids can effectively cover the soil surface, while legumes like medic and Indianhead lentils may conserve more moisture than conventional bare fallow in dryland areas.
- Protect water quality: Cover crops can reduce pollution from sediments, nutrients and chemicals by taking up excess soil nitrogen, reducing erosion and slowing runoff. Authors of the SARE report cite a study conducted on Georgia corn fields that found a rye cover crop “scavenged” between 25 to 100% of residual nitrogen.
Next: Many farmers who try cover crops complain that it costs more to grow them than they’re worth. How do farmers make them work financially, and how long does it take?
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