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Diversifying crops can cut emissions and increase profits

Farmers across the Corn Belt tend to plant rotations of soy and corn. Diversification could boost returns and reduce pollution. Why don't farmers make the switch?

Aerial view of Mardsen Farm in Iowa

The photo above is of Marsden Farm in Iowa. That strip on the far left is corn. It’s bordered by soybean, followed by a second row of corn. Then it’s alfalfa that’s just been mowed and bailed. The rusty red rectangle is a mix of oats and clover. And so on.

Most farms in the area don’t look like barcodes. On around seven out of every 10 Corn Belt acres, growers alternate between just two crops: corn and soybean. These industrial-sized, two-crop rotations are hyper-efficient — this region has helped U.S. agriculture to increase yields over the past half-century without using more land. The flip side is environmental costs: big declines in local biodiversity and high greenhouse gas emissions.

Marsden is different because it’s run by Iowa State University. Since 2001, researchers there have been using the 22-acre site to study what happens when other crops are added to the mix. As best they can, the scientists mimic a regular farm: same kind of equipment; similar use of fertilizers. The hope is that what works at Marsden will make sense commercially. 

The data they’ve gathered shows that diversifying crop rotations does indeed make sense. Last month, for instance, Marsden researchers showed that a four-crop rotation such as the one you see above cuts greenhouse gas emissions by close to two-thirds. Unlike corn and soybean, oats and alfalfa do not require synthetic nitrogen fertilizer, the single biggest source of emissions in the two-crop system.

It takes three or four years before the results of a new system become clear, for example. If the current system is profitable, the jump may seem too risky.

It’s just the latest in a string of positive results from Marsden. Over time, the more diverse crop systems planted there almost eliminated herbicide use; increased corn and soybean yields per acre; reduced the incidence of sudden death syndrome, a key disease affecting Corn Belt soybean; built soil health; reduced fertilizer run-off and cut soil erosion. And, yes, worked commercially: In the most recent paper, researchers find that reduced spending on synthetic fertilizer and other production costs results in a 10 percent increase in net return per acre in the diversified system. 

This kind of result might feel familiar. Marsden is one of many experimental farms that have demonstrated the benefits of diversification and other regenerative techniques. So why do growers persist with the current system?

"Lots of things go into deciding what farmers grow," said Natalie Hunt, the University of Minnesota scientist who is lead author on the new paper. "It’s not entirely economic." It takes three or four years before the results of a new system become clear, for example. If the current system is profitable, the jump may seem too risky. Farmers also need access to a support structure that makes the switch possible, from access to manure to the right kind of crop insurance.

There’s clearly a role for government here, especially as the government created the current situation. Two-crop rotations aren’t some old-timey Midwest tradition — they’re born of policies that date back to the early 1970s, when Earl Butz, President Richard Nixon’s ag secretary, told farmers to "get big or get out." Now, farmers and the industrial complex that surrounds them are locked into the existing system by markets and subsidies that implicitly or explicitly support it.

One bright note: Successive administrations have let this problem develop, but many companies and nonprofits are building workable and profitable solutions.

The challenge of scaling regenerative approaches is something we’ll tackle in a two-part session at next month’s VERGE conference. The keynote sessions are free. A $99 pass — rates go up after today — gets you access to a week of food programming, plus more than 200 sessions on the carbon economy, circular systems, transport and energy.

This article was adapted from the GreenBiz Food Weekly newsletter. Sign up here to receive your own free subscription.

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