Rapid topsoil erosion in parts of Kansas

It’s erosion.

“I don’t even think they know how much they’re losing,” Jodi DeJong-Hughes, a soils and water quality educator at University of Minnesota Extension. “We have this deep, rich, black soil. And it gets a little less each year.”

An eye-popping new report from a leading geologist at the University of Massachusetts Amherst argues that soil erosion in the Midwest — including from samples in southwestern Minnesota — is happening at a far faster clip than previously estimated.

“On a human time scale, the change is pretty much impossible to see,” said UMass Amherst geoscientist Isaac Larsen, whose findings were published this month in the scientific journal, Geology.

Larsen told the Star Tribune last month his research analyzed the lingering shrapnel from exploded stars, specifically beryllium-10, that has been embedded into native, remnant prairie.

Farmers’ plows overturned fields beginning in the 19th century. But by measuring trace amounts of 10Be in virgin prairie, Larsen could better estimate how fast erosion occurs naturally.

“The soil is being eroded 100 times faster than it’s forming,” Larsen said. “And that kind of situation can burn right through the soil profile.”

Larsen and his team traveled to sites across the Upper Midwest, from southwestern Minnesota down to northern Kansas. He said the loss of soil isn’t simply an academic fascination.

This loss — called soil loss tolerance values — has perennially been utilized by the U.S. Department of Agriculture to determine soil health for farmers.

In 1982, the USDA estimated roughly 40% of U.S. cropland was eroding at destructive rates. By 2007, that rate had dipped to below 30%, though it’s slightly increased over the last 15 years.

“We’re certainly getting better over the last 100 years,” said Anna Cates, a soil scientist with the University of Minnesota.

Minnesota exceeds the national rate in the loss of soil caused by wind erosion. And Cates has seen firsthand the destruction caused by soil loss.

This summer, Cates visited fields outside Crookston in the northwestern portion of the state and witnessed farmers frantically replanting dry edible beans following a dust storm.

“The land was scoured,” said Cates, “just scoured.”

Erosion happens many ways. Sometimes, it’s winds depleting a hillock over decades. Other events are more rapid. Those latter events, said Cates, prompt farmers to consider other practices, such as reducing tillage or planting cover crops.

“Every farmer who sees erosion doesn’t make a change,” Cates said. “But every farmer who changes, references erosion as a motivator.”

Larsen said in the aftermath of the Dust Bowl of the 1930s, when the USDA set standards, researchers only understood a shadow of what today’s scientists know about soil loss.

“At the time, the science wasn’t really there like it is now,” said Larsen.

And researchers and teachers with UM Extension say they’re sounding the alarm bells.

On Thursday, a group of soil practitioners met at a conference in St. Cloud. DeJong-Hughes said it’s common for farmers not to think about the latest in science because they often rely upon what their father or grandfather did to plant and till.