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ST. JAMES, MINN. - On Tuesday, it coated the white snow drifts piled up between Hwy. 60 and a farm field.

It spoils a picturesque Minnesota winter scene.

And it looks like an Oreo McFlurry crossed with an oil spill.

It's not a new Roald Dahl book. It's snirt.

A clever portmanteau of "snow" and "dirt," snirt is what you get when black topsoil blows from semifrozen fields to pepper snow.

"Snirt is the bane of rural southern Minnesota in mild, dry winters," said Megan Roberts, agribusiness and food innovation program director at Minnesota State University, Mankato.

Not only is it visually displeasing, it's a symptom of unusual weather conditions in the state: Minnesota lakes and farm fields should be frozen solid in January.

Dorian Gatchell, an agronomist and owner of Minnesota Agriculture Services, said he's seen worse years of the sludgy swirl in western Yellow Medicine County, but this year ranks up there for snirt prevalence.

"We've had very, very dry conditions, and our soil is not as frozen as it usually is," Gatchell said. "For some farmers it's not scary, but it should be."

Topsoil is a farmer's lifeblood. The nutrient-rich dirt can build high yields and enrich the soil for generations of future farmers. But in dry years, when harvested corn and soybean fields remain uncovered by snow, that dirt can blow off down the road.

This snirt is no laughing matter as erosion is a battle for many farmers and can even spread soil diseases, Gatchell said.

Jim VanDerPol, a Chippewa County farmer, said three years ago was the worst year he's ever seen for snirt, "But this winter isn't over yet."

VanDerPol raises livestock on pasture and crops. His farm practices, in theory, should prevent erosion. He tills only 30 acres out of 300. His land is covered during winter with perennial grasses and crops. Over 40 years, he's seen a decrease in erosion. But that doesn't mean less snirt, as sometimes it's coming from the neighbor's field.

"Even if you don't till at all, you're apt to have issues with erosion," VanDerPol said.

Reached for comment on snirt, the National Weather Service in Chanhassen declined to comment.

But the agency did confirm wind gusts reached 30 mph along the Interstate 90 corridor last week, sweeping over the Minnesota prairie.

And the snirt flew. By Monday, dirt speckled the remaining snow piles.