ROBERT SIEGEL, HOST:
A lot of big food companies have promised to do their part to slow down climate change. As we reported yesterday, that quest has been surprisingly complicated. That's because many of those greenhouse emissions are the result of farmers giving their crops the nutrients they need. Any real change could reshape the landscape of American farms. NPR's Dan Charles picks up the story.
DAN CHARLES, BYLINE: All over the Midwest in farm country, you see businesses like Key Cooperative in Grinnell, Iowa. It's a farm supply place. It sells seeds and pesticides and fertilizer.
So this is the Corn Belt.
BRENT DEPPE: Yep. It's sitting in the middle of it.
CHARLES: Brent Deppe is one of the managers here. We step through the back door of the co-op, and there's a big, white, round storage tank.
This is a huge tank. What's in here?
DEPPE: This is the liquid nitrogen tank. It's a million-and-a-half-gallon tank.
CHARLES: Nitrogen is the most important fertilizer. It's like the fuel that drives the production of food.
How much nitrogen goes out of here in a year?
DEPPE: Not enough since I'm in charge of sales.
CHARLES: For the environment, though, the answer is way too much. Manufacturing that fertilizer releases lots of carbon dioxide into the air. And then when farmers spread it on their fields, most of it doesn't stay there. Rainfall washes it into streams and lakes. And Philip Robertson, a researcher at Michigan State University, says some of the rest becomes food for bacteria in the soil.
PHILIP ROBERTSON: These bacteria are there naturally, but once they get exposed to fertilizer nitrogen, they really light up.
CHARLES: And they release a super powerful greenhouse gas called nitrous oxide. Nitrogen pollution is a huge global problem, and a few years ago, food companies like Walmart and General Mills started to talk about how to reduce greenhouse emissions from fertilizer. This caught the attention of a man named Matt Carstens.
MATT CARSTENS: So it got pretty specific where they were targeting, and that kind of hit close to home for me with a farming operation that I'm from here in Iowa.
CHARLES: Carstens was also selling fertilizer at the time for a company called United Suppliers. He got so interested he flew to Washington, D.C., to meet with the Environmental Defense Fund, an advocacy group that was working with Walmart on ways to reduce the climate impact of the food it sells.
CARSTENS: You can't help but sit back as somebody that's deeply entrenched in agriculture and go, we've got to understand this. And again, you can take two approaches at that point. You can try to fight it, or you can try to be a part of whatever solutions are out there.
CHARLES: On the flight home, Carstens thought to himself, I know some solutions. Maybe I could build a business selling them to farmers, solutions like chemicals you can mix with a nitrogen fertilizer to keep it from washing away so quickly or computer programs that show farmers how much nitrogen is in their soil so they don't add more than they need. It'll work, he thought, if those tools put more money in farmers' pockets, if it means they can spend less on fertilizer per bushel of corn.
CARSTENS: You can't go to the farm and just say, you have to do this because. We have to put it in a way that is economical and profitable for them.
CHARLES: Carstens turned that brainstorm into a program that farmers can sign up for. He called it SUSTAIN. Then two years ago, Land O'Lakes, a giant agricultural co-operative that spans the country, bought his company and adopted his program, took it national. Environmental groups have praised it. Walmart wants farmers to sign up for this to help the company reduce its greenhouse gas emissions. The real test, though, is what happens at places like Key Cooperative in Grinnell, Iowa, where this program meets farmers like Ben Lauden.
BEN LAUDEN: We're all row crops, which are soybeans and corn. I raise about 1,800 acres.
CHARLES: Lauden has signed up with SUSTAIN. He's doing all those things that are supposed to let him use nitrogen more efficiently. But he's not sure if it means he'll really end up using less of it.
LAUDEN: I think you would use less, but I don't - I can't quantify it (laughter) I guess.
CHARLES: If he does use less, it won't be much less. He and Brent Deppe, the manager from the co-op, both say farmers already use nitrogen efficiently. For them, this program is mainly a way to get that message to consumers, which is why some environmentalists say despite all the corporate cheerleading for SUSTAIN, it's just tinkering around the edges of agriculture. Food companies could do so much more.
Sarah Carlson, who works for a group of environmentally minded farmers called the Practical Farmers of Iowa, has confronted Walmart executives about this.
SARAH CARLSON: I was, like, why are you only focused on nitrogen fertilizer management? Like, that just makes such little impact on water quality and such little impact on greenhouse gas reduction.
CHARLES: Carlson says here's what you really need to do. Give farmers a financial incentive to move beyond just growing corn and soybeans. Bring back small grains like oats, for instance. That small change can have a big impact, she says, because farmers can combine oats with a so-called cover crop of clover. That clover adds nitrogen to the soil the organic way - no synthetic fertilizer needed. Plus, cover crops add carbon to the soil - also good for climate change.
CARLSON: You know, maybe, Walmart, you should suggest to your commodity buyers they buy more small grains for feed rations.
CHARLES: Feed rations for cattle or pigs.
CARLSON: We have all these pigs in the state. Five percent of their diet could be oats. Like, we can just sprinkle it in there.
CHARLES: Just one crucial obstacle - relying on oats for your bacon costs a little more money, and somebody would have to pay to make it happen, like Walmart and, in turn, American consumers. Dan Charles, NPR News.
[POST-BROADCAST CORRECTION: In the audio of this story, we state that most nitrogen fertilizer that farmers add to their fields is lost to the surrounding water and air. In fact, only some of the fertilizer is lost, and most is used by the growing crop.]
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.