Cropping Between the Lines

The bull’s-eye on corn ethanol could fade if the industry steps up and makes corn production and stover harvesting more environmentally friendly
By Holly Jessen | October 18, 2011

Conventional wisdom has long held that cropland should sit fallow over winter, with nothing growing on it. “That was absolutely the stupidest thing we have ever thought of in the world,” says Jim Hoorman, a member of the executive committee of the Midwest Cover Crop Council.

Today, no-till or strip-till farming is gaining ground, and researchers are examining systems that combine reduced tillage with planting perennial or annual cover crops. Instead of competing with the primary crop for nitrogen and water, as once was feared, planting cover crops offers farmers a way to improve the soil. Other benefits range from reducing erosion and water quality problems to increasing soil organic matter levels as well as providing insect and weed suppression.

This summer, Iowa State University revealed the results of a three-year study of cover crops in corn fields. The study found that planting a perennial cover crop with corn can keep soil, nutrients and carbon in the fields while providing corn yields equal to traditional farming methods. Unlike annual cover crops, which are planted in the fall and killed off in the spring, perennial cover crops save time and money on seeding, says Jeremy Singer, a research agronomist with the National Laboratory for Agriculture and the Environment, who participated in the ISU study.

It’s exciting news not just for corn producers, but for the ethanol industry. With corn stover high on the list of possible cellulosic feedstocks, many have wondered how much of it can be harvested before the scale tips and the practice harms the land. It’s clear that harvesting all the stover wouldn’t be a good idea. “[That would remove] the last buffer against severe soil erosion and severe environmental issues related to that practice,” says Ken Moore, a distinguished professor of agronomy at ISU and one of the researchers who worked on the perennial cover crop study.

In this way, cover crops provide an answer to the food vs. fuel debate—corn producers can truly produce feed and fuel from their corn crops, Singer says. “By using the cover crop you are protecting the soil, you are increasing nutrient cycling, you are offsetting a lot of the carbon that is being harvested in the stover,” he says. “We feel like you can harvest as much of the corn stover as you want, basically.”

Cover cropping addresses water quality concerns as well, such as the hypoxic zone in the Gulf of Mexico where nutrient runoff from the Mississippi River watershed creates a dead zone. Crops growing on the land only four months out the year add up to “sort of a leaky system,” Singer says. Nitrogen in the soil turns into nitrate, which can leach through the soil and contaminate surface and ground water. Cover crops help capture that nitrogen in the spring and fall. “It could help take corn off the bad list—that’s sort of the take home message of this,” he says.

Moore agrees. “This will make the whole system sustainable,” he says. “Nobody can really complain, under this system, that corn production is having severe adverse impacts on the environment.”

From Lawn to the Field

In every study, there are winners and losers. ISU’s study, which was funded by a Sun Grant for biobased research, identified Kentucky bluegrass—a common lawn turf—as a recommended perennial cover crop for corn. Thirty-five potential ground covers were screened to identify crops that, with little or no suppression, did not compete with corn, Moore says. Different corn hybrids were also tested to discover if there were varieties that worked better in a cover cropping system. The final component was determining which agronomic practices would be required to grow corn with perennial cover crops.

On the ground cover side, researchers identified a number of species that would work. “It turns out, based on our work, that just about any one will work as long as it’s suppressed and can take the suppression,” Moore says.

What made Kentucky bluegrass stand out from the crowd is how easy and inexpensive it is to purchase the seed. “It’s a very common plant in the Midwest,” he says. “It’s in everybody’s lawn—if everybody is lucky, it would be the only one in their lawn.” In addition, farmers are already very familiar with controlling it. “I think if we brought in an exotic species for a ground cover they would balk at that initially,” he says.

The study also revealed some winners and losers in corn hybrids. In other words, some hybrids performed better with cover crop competition, leaving the door open for further research and genetic work.  “We believe there is scope for improving the corn hybrids to grow better in a companion situation with a cover crop,” he says.

Finally, researchers mapped out exactly how to grow cover crops with corn. The combination that worked the best was a fall strip till about 4 inches wide combined with herbicide use, Singer says. In the spring, either before corn is planted or before it has emerged, they applied Paraquat, a contact herbicide, to burn back the green tissue of the grass without killing the plant completely. “So that buys corn some time,” Singer says. Then, as the corn starts to canopy, they applied a 10-inch band of Round Up to the herbicide-tolerant corn. “Just to make sure that we have that zone of no competition right over the row,” he adds. Then, during summer and fall, the grass begins to grow back before going dormant in the winter. Maintenance seeding may be needed every three to five years.

The most exciting results of the study were that corn yields with cover crops under this system were essentially the same as the control. In addition, no extra fertilizer was needed. “We didn’t have to increase the nitrogen rate to achieve that,” Singer says. “That’s a significant finding.”

At this point, the researchers aren’t recommending wide-scale perennial cover cropping for corn growers. “We’re not ready for prime time yet, but we think it’s absolutely doable,” Moore says. Additional research needs to be done to quantify the impact on nitrogen levels in a cover crop system. The question is, what’s the actual financial benefit—the return to producers—in increased soil productivity? If soil improves, that could be a selling point for producers. “The struggle with cover crops, whether they are annuals or perennials, any type of cover crops, has just been penciling out the cash benefits, the return to the producer, because a lot of the functions cover crops perform are longer term,” Singer explains.

So what needs to happen for cover cropping to catch on nationally? Iowa has seen a pretty dramatic increase due to a cost share program that provides USDA funding for cover crops in watershed states bordering the Mississippi River. Funding is available through the Natural Resources Conservation Service, with varying funding levels in different states and even among different counties within the same state. Still, Singer doesn’t feel that type of incentive is what’s going to work in the end. “I don’t think that government cost share is sustainable,” he says. “Government is shrinking right now—funding is shrinking for conservation practices. You can’t rely on cost sharing to increase adoption for producers.”

What’s really needed is for an industry or service sector to step up and help establish cover crops. That could mean agribusiness or, specifically, the ethanol industry. The motivation there would be a mutual effort to get the bull’s-eye off the back of corn-ethanol. “The corn ethanol industry depends a lot on farming and it’s important to your industry that farming keep sustainable,” Moore says.

Other Angles

It’s clear that soil should have something living and growing on it year round, says Hoorman, who, besides serving on the cover crop council, is a cover crops and water quality specialist for Ohio State University extension service. The more soil is used—the more plants growing on it—the healthier it becomes. He, like others, sees the exciting possibilities of using cover crops in concert with bioenergy feedstocks. “It would be a great way to give us that three-legged stool, for food, fiber and also fuel,” he says.    

Research at OSU has shown that cover crops in a continuous, no-till corn/soybean/wheat rotation can produce enough nitrogen to compliment or even replace fertilizer for corn production. Seven years of research identified two annuals, cow pea and winter pea, as ideal cover crops. “Cover crops produce enough nitrogen to where farmers many not need to add nitrogen fertilizer to their corn crop, but if they want to be sure of maximizing their yields, farmers can supplement the cover crops with 25 to 30 pounds of nitrogen fertilizer,” says Rafiq Islam, an OSU Extension soil scientist in a 2010 press release about the research. “That’s more than enough a farmer needs to support the corn crop.”

Commercial fertilizer wasn’t widely used until about World War II, Hoorman tells EPM. As time went on, farmers started using more fertilizer and growing more monocultures. In the 1980s, the U.S. imported 24 percent of the nitrogen used and by 2010, that number had increased to more than 60 percent, according to information from OSU.

Changing fertilizer practices is part of a movement to ecological farming—ecofarming—which includes eternal or exclusive no-till, cover crops and other best practices. “By working with Mother Nature, we’re finding we can produce maybe even better crops, higher yielding crops, than what we could before,” he says, “Because the one thing we really ignored was our soil quality.”

Brazil has used the concept of ecofarming or eco-agriculture for the past 30 years. Starting with worn out soils, the country has increased its soil productivity through the use of cover crops and is now producing 40 to even 60 bushel soybeans. “As our soils in the United States are decreasing in value and productively, theirs are increasing,” Hoorman says. “They are taking worn out soils and making them better.” 

In Michigan, researchers looking at cereal rye, another annual cover crop, for use with corn, combined cereal rye cover crops with 10- to 15-inch strip till. Since cover crops keep the soil temperature lower, the strip till gives the soil a chance to warm up to encourage faster corn germination, says Dale Mutch, a senior extension agent at Michigan State University.
With an annual cover crop, one of the challenges is timing. Michigan has a shorter growing season than Iowa and it can be difficult to get the cover crop planted quickly enough in the fall to provide the full benefit through the winter. One idea researchers are looking into is aerial applied cover crops, Mutch says. With a corn crop, the cover crop seed would probably be applied in the last part of August, giving it time to establish itself before harvest.

Author: Holly Jessen
Associate Editor, Ethanol Producer Magazine
(701) 738-4946



Cover Crop Veteran

Dave Brandt, a farmer from Carroll, Ohio, first incorporated no-till into his operation in 1971 and added cover crops in 1978. He uses a corn/soybean/wheat rotation on his farm and is an enthusiastic promoter of cover crops. When Brandt talked to EPM in September, he had about 350 acres of radishes and winter peas already planted for the winter cover crop. He was in the midst of harvesting another 300 acres of corn on land in which radishes and winter peas were planted the previous fall, and another 40 acres of corn that had been previously planted with hairy vetch as a winter cover crop.

Cover crops supply nitrogen and nutrients to the next crop. Brandt has found that planting winter peas and radishes reduces needed nitrogen inputs by about 75 percent, while hairy vetch reduces it by about 60 percent. In addition, it costs much less to plant cover crops than it does to fertilize, he says. Planting winter peas and hairy vetch costs him only $17.50 an acre, although that doesn’t include his time and equipment. Fertilizer, on the other hand, costs about $120 an acre at this fall’s prices. “We saved about half of our nitrogen costs, including the seed,” he says.

He’s also gotten some good results protecting sloped ground from erosion. Starting at normal tolerated soil loss, Brandt has reduced soil erosion on his farm to less than 50 to 80 percent using cover crops.

The long-term benefits are perhaps even more impressive. Brandt’s soil has gone from organic matter readings of half a percent to as high as 4.5 and 5 percent. That gain in organic matter adds up to measurable improvements in the crops themselves. “We have done some work with grain sampling and we found that our no-till corn with cover have more nutrients than corn that is in a corn/bean conventional rotation,” he says.

In general, Brandt finds that winter peas and radishes freeze out over a hard winter, while still providing the benefits of a cover crop. Hairy vetch, on the other hand, stays green all winter and needs to be suppressed in the spring before planting.

No-till and cover crops do take a little more management, he says. It can be a difficult switch for those used to doing things a certain way—some ever since their grandfathers farmed the land. “You have to change your mindset if you are going to grow covers,” he says, advising farmers to start small so they can see the benefits for themselves.

—Holly Jessen