Snirt: A Black & White Issue

To anyone driving through rural Minnesota the past few weeks, the images featured in the slideshow below will look familiar. In a sense, the black and white swirls of "snirt"—a mash-up of the words "snow" and "dirt"—have the look of beautiful impressionistic paintings wrought by a wind-borne hand.

But these photos, which, with the exception of the last one, were all taken within the past month in western Minnesota, reveal an ugly truth: our land is suffering mightily from an annual cropping system that covers it only around 90 days a year. A white snowbank has a way of showing up the previous season's land use sins.

Last year at this time we wrote a blog about the prevalence of snirt-filled ditches throughout the Midwest. At the time, it seemed to be the worst case of winter erosion many people could remember. But recent reports from across the Corn Belt reveal that 2015 is proving to be even dirtier. And we haven't even gotten to mid-February yet, when ground blizzards combined with freeze-thaw cycles can churn up more soil. And then there's spring, when downpours and runoff on bare fields can dig into the soil profile itself, using hydro-power to form gullies and rills.

Why all the snirt in January? Once row crops like corn and soybeans are harvested in the fall, the soil is often tilled to get a jump-start on the following growing season, leaving the land bare until May, at best. Early snows can provide a modicum of protection, but a mid-winter thaw combined with a scouring wind can fast prove how little armor the land really has. All this snirt is also a sign that the soil is so impoverished biologically—removing plant cover above ground starves microbes beneath the surface—that it can't resist being blown about by even relatively minor wind events.

Snirt reveals that intense rains are not the only cause of serious erosion—wind on flat-as-a-pancake land can loosen immense amount of soil. A color-coded USDA map makes it look like western Minnesota has a case of the chicken pox, with each red dot representing 100,000 tons of soil lost to wind annually.

Much of this erosion is taking place on land that formerly was in pasture, hay or even habitat enrolled in the Conservation Reserve Program. Often this is land that previously would not have been cropped, since it was considered too marginal to produce a profitable corn or soybean yield.

But government initiatives like subsidized crop insurance have taken the risk out of tilling such lands. The result is a landscape that, on a brisk winter day, can resemble something out of an apocalyptic nightmare.

Perhaps the most troubling photo is the last one in the series. It was taken in May, after the winter snows have melted. That soil, which is supposed to be in an adjacent field, is instead clogging a culvert. At a time of year when our black gold is supposed to be beginning its job of producing food, it's instead occupying the role of messy nuisance. It's at this point that live soil becomes dead dirt.

Brian DeVore is the editor of the Land Stewardship Letter. Thanks to Julia Ahlers Ness, John White, Terry VanDerPol, Darwin Dyce and Andy Marcum for supplying erosion photos for the slideshow.