How U.S. Soybean Farmers Are Making Their Fields More Sustainable

For a plant native to Asia that was first domesticated 9,000 years ago, soy has become surprisingly popular in the United States. The country is one of the world’s largest soy producers, having increased its output by 55 percent since 2000, according to research from Our World in Data. One might think vegetarians’ penchant for tofu is fueling this rise, but in reality, the vast majority of soy is used as animal feed. 

While they are a high-quality source of protein and energy for animals, soybeans come with a planetary price. Global soybean production is linked with deforestation, habitat degradation, soil erosion and water pollution. After beef and palm oil, soy production is one of the main drivers of tropical deforestation — especially in Brazil and other parts of Central and South America.

But American soy farmers are starting to do things differently. Since 1980, they’ve reduced greenhouse gas emissions per bushel by 42 percent, according to the U.S. Soybean Export Council. As a result, U.S. soy has a much lower carbon footprint than many other soy-producing countries. Over the same period, farmers also increased land use efficiency by 47 percent and energy use efficiency by 45 percent, according to the council. 

By adopting techniques like conservation tillage, agroforestry and buffer strips, U.S. farmers are putting soy back on the sustainability map.

Planting prairies on soybean farms

U.S. soy farmers are using a wide variety of techniques to adapt to climate change, improve soil quality and ensure food security. One such method involves planting native prairie strips along the contours and edges of fields. 

“If you can take 10 percent of the field out of production and plant it to a narrow strip of prairie, it's as good as a terrace as far as keeping soil in place and preventing nutrient runoff,” said Paul Mugge, who grows organic soybeans, corn, grain and alfalfa in Iowa. “They're very, very effective, and you get all these other benefits, too. It's habitat for pollinator insects. It's habitat for beneficial insects.”

These narrow vegetation bands cover the soil, slow water flow and anchor the soil with deep-rooted plants. As a result, converting just 10 percent of fields into prairie strips can reduce water pollution — particularly the phosphorus and nitrogen carried away in runoff — and soil erosion by 85 percent or more, according to research from Iowa State University.

Another similar practice is beetle banks. On Mugge’s farm, these raised strips of land are planted with bunch grasses — which grow in clumps or tufts — and positioned next to the prairie strips.

“That's habitat for some seed predator insects,” Mugge said, referring to bugs that eat seeds. “Because it turns out that if you don't do fall tillage, if you leave those weed seeds on the surface for a period of time — like in my case with soybeans where they're basically no-till for seven months — 70 percent of those weed seeds are eaten by field crickets or carabid beetles. So that's helping me a lot, too.”

Besides reducing pests and weeds, beetle banks and prairie strips provide habitat for native birds and mammals. Since these strips take farmland out of production and cost money to install, the United States Department of Agriculture's Conservation Reserve Program offers financial assistance for these efforts. 

Switching up the location 

While prairie strips have only been a common practice for around two decades, not all sustainability tools are so contemporary. Crop rotation — which involves planting different crops in the same area across multiple growing seasons — has been used since Roman times. For example, a three-year crop rotation could include planting soybeans the first year, tomatoes the second, corn the third and soybeans again in the fourth year. This strategy improves soil health and biodiversity, but it has another advantage: pest control.

For instance, crop rotations can combat one of the plant's most destructive pests: soybean cyst nematode. By rotating in crops that it can’t use as a host, farmers can reduce populations of this soil-dwelling roundworm by up to 55 percent, according to research from Purdue University. But it can take several years of non-host crops to lower their numbers sufficiently. 

In addition to crop rotation, Mugge also plants cover crops, which are meant to protect the soil rather than be harvested. He plants red clover after the grain rotation, which adds nutrients to the soil when  left to decompose in the field.

“I get 80 to 100 pounds of nitrogen for the following corn crop from the clover crop because it's a legume,” Mugge said. “I've done that forever, too.”

Cover crops reduce soil erosion and water pollution, limit pests, and can even improve crop yields. But they require time and money to plant and terminate.

Despite this plethora of pest-control methods, U.S. soybean farmers increased their use of pesticides over the last two decades. Mugge’s practices leave his farm standing in stark contrast to the norm.

“I really haven't had serious insect issues,” Mugge said. “Part of that is because of the rotation and letting Mother Nature work the way it's supposed to. I'm not spraying things, so I've got lots of beneficial insects.”

Climate change on the farm

Soybean farmers are also tackling another problem: climate change. By foregoing synthetic pesticides or fertilizer, Mugge’s organic operation already has a leg up.

“On average, I use probably two-thirds of the fossil fuel energy per acre that the conventional guy does,” Mugge said. 

In a study published in the journal Communications Earth and Environment last year, for example, producing a wide range of organically farmed products used 32 percent less energy and emitted 22 percent less greenhouse gas emissions per area than conventional products. But organic products required more land on average than their conventional counterparts. 

Organic farmers have another trick up their sleeves: developing more organic matter in the soil. Made of both living and decomposing plant and animal tissue, organic matter can store carbon in the soil.

“My soil organic matter is mostly over 5 percent, whereas my neighbors’ are more like 3 percent — which doesn't sound like much,” Mugge said. “But if you figure that 2 percent of organic matter is a lot of pounds of organic matter, which is a lot of pounds of carbon, which is even more pounds of carbon dioxide which is kept out of the atmosphere, really every year… we're pretty climate-friendly.”

Besides the potential climate benefit, soil organic matter boosts the soil’s capacity to hold water and nutrients while also decreasing erosion and runoff. Plus, minimal or no tilling is used on over 74 percent of U.S. soybean acres, according to the industry group United Soybean Board. This technique essentially means not disturbing soil, and it helps reduce soil erosion and greenhouse gas emissions, improve air and water quality, and boost soil health.

Mugge uses some tilling to suppress weeds since he doesn’t apply synthetic pesticides. But he strives to minimize this practice. 

Global soy production has doubled since 2000. And though a very small percentage of soybean acres are organic in the U.S., Mugge has noticed increased growth of organic soy farming in his area.

“I was the only one in my county for a long time, and that was kind of lonely,” Mugge said. “Now there's probably a dozen of us in my county, and it continues to grow. There's a big demand for organic stuff that is not really being met at the moment, so people are kind of finally figuring out what Europeans have figured out for a long time — that we really are what we eat.”