A defense against flooding: Healthy soil

Opinion editor’s note: Editorials represent the opinions of the Star Tribune Editorial Board, which operates independently from the newsroom.

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Watching floodwaters devastate some of Minnesota’s most productive cropland in recent weeks has been agonizing for the state’s farmers and heartbreaking for city folks who care about their rural neighbors. It’s easy to feel helpless in the face of climate change and what seems like an endless series of extreme weather events.

But Minnesota doesn’t have to be helpless. There are simple and proven practices that farmers can adopt, with support from state and federal agencies, that can help protect their fields from floods and droughts — and reduce flood damage across the rest of the state as well.

That’s because, in recent decades, agronomists have made huge breakthroughs in understanding the soil beneath our feet and the way it adapts to changing conditions. It turns out that soil is more than just a layer of dirt. It is a living ecosystem — full of fungi, rhizomes, tiny worms, microscopic insects and useful bacteria — that is capable of constant adaptation and regeneration. How complex is this hidden world? Scientists estimate that just one tablespoon of healthy Midwestern soil can contain more microorganisms than the human population on Earth.

It turns out that healthy soil not only produces healthy crops, it’s a magnificent buffer against flooding and drought. Healthy soil has a spongy quality that can absorb and hold huge amounts of water in big rainstorms. According to the Natural Resources Defense Council, an acre of healthy soil can hold 20,000 to 40,000 more gallons of water than soil that is robbed of its organic matter.

Sadly, modern farming practices tend to sabotage these remarkable properties. Healthy soil, like much of the natural world, requires diverse plant life; an older generation of Minnesotans will remember when farmers raised oats, alfalfa, barley, flax, sunflowers and other crops that, in combination, regenerated the land. Today, farm fields of the Upper Midwest are 80-90% corn and soybeans, a monoculture that tends to deplete the soil. To make matters worse, frequent tillage by heavy machinery compacts the soil, leaving it less absorbent.

Fortunately, this same research has validated a number of farming practices that can restore soil health. Planting cover crops such as winter rye and hairy vetch (crops that are sowed after the fall harvest and blanket the ground until spring) reduces erosion, feeds the ground’s living organisms and provides rich organic matter to rebuild soil. No-till and low-till plowing — techniques that cause less disturbance to the ground and its organisms — also help build soil health. These practices, in turn, rebuild the land’s buffering powers. Andrea Basche of the University of Nebraska has estimated that greater use of cover crops and perennial plants in erodible places could have reduced rainfall runoff into the Missouri River by at least 13% in the wet year of 2011 and reduced flooding frequency in eastern Iowa by 20% in the epic flood year of 1993. These practices help farmers as well. Farmers who’ve tried them in Iowa and Minnesota report that their fields less muddy in a wet spring, allowing them to get an early start on planting, and more moist through the hot months of late summer.

Sadly, adoption of these techniques has been slow. In Minnesota, for example, only about 1 in 10 farmers uses cover crops and only about one in four practices reduced tillage. Why? For one, many farmers are reluctant to depart from the familiar. And for good reason — one bad gamble and you lose the family farm. For another, they generally cost money upfront to buy specialized machinery such as no-till seed drills. “It’s the right choice, but you feel like you’re just writing one more check in the spring,” says Brad Jordahl Redlin of the Minnesota Department of Agriculture.

To address these barriers the Legislature created a soil health grant program in 2022 to subsidize the cost of specialized farming equipment. Farmers submit competitive grants showing the kind of implements they need and how it would improve their soil. Even though the grants are modest — an average of $29,000 the first year — the program was an instant hit. More than 500 farmers have applied in the first two years and applications are outrunning the available funding by more than 3 to 1. An older but related federal project, the Conservation Stewardship Program, is also oversubscribed and underfunded. If we’re serious about changing agriculture and making rural America more climate resilient, these programs need a boost.

Given how much we have warmed the Earth in recent decades, it’s clearly too late to fend off early and catastrophic effects like this summer’s floods. But it’s not too late to harness the Earth’s own restorative powers to buffer that damage in coming years.