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How Growing Corn Could Produce Less Pollution

The greenhouse gases emitted by corn farmers could be cut by more than half, using better farming practices



Michael Gil/Flickr

In a little corner of the Great Plains, corn growers are using proven methods to cut their carbon footprint.

The tri-state corner of Minnesota, South Dakota and Iowa is marked by rolling hills dotted with trees, a transition between the dry prairies and woodlands. Recently, it has become a laboratory for more sustainable corn, and one research team has found that the processes used can cut carbon emissions by more than half from the national average.

The management practices, outlined in an as-yet-unpublished study, are surprisingly straightforward. Here, farmers spread manure from their cattle operations, and some use GPS systems to maximize efficiency. They intersperse their corn with cover crops, plants that infuse nitrogen into the soil, which lowers the need for synthetic fertilizer. They significantly reduce soil disturbance with less tilling, the practice of digging up the ground to plant seeds and remove weeds.

"There's no magic bullet," said David Kolsrud, a Sioux Falls, S.D.-area farmer and owner of DAK Renewable Energy, an ethanol company. "We use agronomy practices well-known to us, but utilized in a matter that can maximize the amount of product per acre without overdoing it."

Corn yields in this region are about 20 percent higher than average. At the same time, farmers are able to displace about 14 percent of industrial fertilizer with manure. Emissions of nitrous oxide -- a greenhouse gas with close to 900 times the global warming potential of carbon dioxide -- are more than one-third lower than the national average.

Keith Alverson and his family have been using a method called ridge tilling for the last three decades on their Chester, S.D., farm. A modification to the traditional way of tilling soil, ridge tilling allows Alverson to clear out weeds and warm up the soil -- advantages of tilling -- while reducing the release of carbon dioxide and nitrous oxide and keeping soils rich with necessary carbon.

"A lot of these things require a little more management, attention to detail," he said. "But we get benefits on multiple levels, benefits for those on the farm and benefits for those across the nation."

These growers have the cold northern climate to thank for making these practices easy. The cold winters prevent too much nitrogen leaching in the soil, and growers can apply a light, more efficient layer of nitrogen fertilizer. A dry springtime in the region also helps. No-till farming and low-till farming can be challenging in rainy regions, he said, because the soils get too wet to properly manage them.

Some growers, wary of another event like the 2012 drought that devastated the Corn Belt, may choose to play it safe by planting early. This requires dredging and drying the muddy soils before the usual start of planting season, said Barry Fisher, a state soil health specialist and agronomist with the Agriculture Department's Natural Resources Conservation Service (NRCS) office in Indiana.

Higher yields for lower GHGs
Three years ago, renewable fuel company Gevo purchased an ethanol plant in Luverne, Minn., in the heart of the region, to produce isobutanol -- a corn-based cousin of ethanol that doesn't need to be blended with gasoline and could qualify as an advanced biofuel under the federal renewable fuel standard. Gevo bought the plant from the Cornerstone Farmers Cooperative, of which Kolsrud is a member.

"Gevo wanted to find out just how sustainable their greenhouse gas footprint looked," said Jack Huttner, who worked at Gevo when the study was initiated and now leads Huttner Strategies, a consulting firm.

With the oversight of John Sheehan, a professor at the University of Minnesota's Institute on the Environment, Gevo released a survey to nearly 350 farmers in the region, potential suppliers of corn to the Luverne plant. About 35 farms were chosen and studied over three years.

The study found that 40 percent of farmers use livestock manure to fertilize their fields on part of their cropland, rather than synthetic fertilizers made with natural gas. Higher corn yields also lead to lower fuel consumption per kilogram of corn.

Now Sheehan is preparing to submit new numbers on the farming practices to peer review, this time using a newly updated model from Colorado State University researchers. It quantifies the amount of carbon that remains in the soil of these farmers' fields, due to no-till and low-till practices. The change is remarkable, said Sheehan.

"I kept going back to the CSU guys, asking, 'Are you sure this is for real?'" he said. "I think these reflect genuine improvements on the model."

These farmers, according to Sheehan's latest estimates, produce corn that requires, on average, 164 grams of CO2 per kilogram of grain. The U.S. average is 371 grams, according to studies from Argonne National Laboratory.

No-till could be the biggest deciding factor in how well a crop can perform. Most corn growers in the United States till their soils, preventing the sequestration of carbon and releasing nitrous oxide. Manure management and livestock integration are the toughest changes to make, he said, as concentrated feedlots have largely disconnected cattle raising and pastures.

"There is a real cost, economic and environmental, associated with getting that manure to the farm," said Sheehan.

Farmers are like 'shoppers on Black Friday'
Changing tilling practices has been a tough sell to farmers nationwide. There are several reasons farmers are averse to no-till or conservation tillage, said Fisher of the NRCS. The main barrier is the fear of change.

"Our internal risk alarm goes off," Fisher said of the farmers. With about $500 per acre of variable costs at stake, it's a lot to bring to the table.

Harmful insects and fungi proliferate in unturned soil. Although soil amendments and seed technology exist to overcome these barriers, many of these farmers tried two decades when the tools were not available. Growers also find it difficult to change the nutrient management system they have relied on for decades.

Advertising influence is at play, too. Agricultural equipment companies don't tout technologies, like no-till, that do away with the rotary tiller or other machines.

"Farmers are no different that shoppers on Black Friday," he said. "There's a lot of advertising on tillage and tillage equipment, and they receive mixed signals from it."

The percentage of corn acres in Indiana that were not tilled or were minimally tilled jumped from 36 percent to 45 percent between 2004 and 2009, according to the state's Conservation Tillage Program. Since then, the level has remained stagnant.

Nevertheless, said Fisher, farmers know soils are not functioning as well as they once did. Although the adoption of low-till and manure management is low, growers are beginning to realize they can make up for potential yield losses and improve their soil's water-holding capacity.

"They are really taking to the soil health campaign and the message," he said. "At any time, you can reverse the loss process, you can turn that around."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

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