Dust storms fueled by climate change, tillage, and drought are causing the loss of tons of topsoil throughout the Great Plains.
Dust storms fueled by climate change, tillage, and drought are causing the loss of tons of topsoil throughout the Great Plains.
June 6, 2022
When he saw a roiling thunder bank of black clouds blowing into Salem, South Dakota, last month, farmer Kurt Stiefvater thought it would take 20 minutes to reach his property. It took five. “I couldn’t believe how fast it was moving,” he says of the over 100-mile-per-hour gusts.
Not only did that wind event—technically categorized as both a derecho and a haboob—send soil airborne, it unearthed wet crop residue. “I had some oats that were about three inches or so—and it sheered them off,” he says. “I couldn’t believe it pulled up that amount of dirt; we had just had two inches of rain two days before,” he recalls. The line of thunderstorms, which developed in Nebraska, raced into eastern South Dakota, northwestern Iowa, and western Minnesota. On his farm, Stiefvater says, the dust storm lasted only about 25 minutes.
“They saw this storm as one freak event. I don’t think they comprehend how much soil they are losing.”
“I was hoping [the soil] would stay in place better,” says Stiefvater, who grows corn, soybeans, alfalfa, and oats on his 1,800-acre crop operation. But, ultimately, he was one of the lucky ones. The storm killed two people, downed power lines, and most of his neighbors in the town of 1,500 saw damage to their houses, sheds, and grain bins. Not only was he in a safer location, but his approach to soil management as a farmer who grows cover crops and practices no-till likely helped him avoid bigger losses.
Overall the region lacks dust monitoring infrastructure, and the single air quality sensor in Sioux Falls suffered a power outage the day of the storm, making it impossible for local scientists to accurately gauge the actual dust concentration in the air the day the storm hit. But two weeks after the storm, the U.S. Department of Agriculture’s National Resources Conservation Service (NRCS) generated rough estimates of soil loss during the event on a hypothetical 100-acre bare field. Given the fact that the storm hit during planting season in an area that doesn’t have much conservation tillage or cover crop usage, it’s fair to assume the estimate applies to many of the impacted fields. Erosion estimates for the day the storm hit range from 3 to 12 tons of lost soil per acre, said Chris Coreil, a Fort Worth, Texas-based soil erosion specialist at NRCS, in an email.
But what’s striking is that Coreil also ran the model for another day a week earlier that had sustained high winds, and found that farmers had lost even more soil—his estimate ranged from 3 to 29 tons per acre—without a dramatic storm. To compare, the maximum amount of soil experts say farmers in the region can lose before it impacts their production levels is 5 tons per acre, per year.
“If you had bare, dry, and unprotected fields on [both days], you probably exceeded the acceptable amount of annual soil loss on each of those days,” he explained. “Farms that use conservation practices are on the lower end of the range . . . and those with bare, tilled fields are on the high end.” For instance, if the soil most prone to wind erosion—a loamy fine sand—was covered with residue or had a crop actively growing in it at the time, it would have lost only a fraction of a ton on both of these days, explained Coreil.
Neither derechos nor haboobs are common in the Northern Plains states. But dusty conditions have been on the rise as a result of the drought. “We’ve been getting more frequent reports of these dust events, and this year the reports have been the most I remember,” says Eugene Backhaus, a state resource conservationist with NRCS in Denver, Colorado—a region, he points out, that was the epicenter of last century’s Dust Bowl. Backhaus says his office doesn’t even try to calculate the soil loss for large-scale events—rather they run those models for individual producers. “They are concerned,” he says.
And although it’s well-known that farming with the soil in mind and using regenerative practices can reduce the impact, it’s not clear whether the increase in dust storms throughout the Farm Belt will cause farmers to reflect and invest in different practices.
“The wind events, with the drought widespread in the plains, are feeding on each other, because any wind on poorly-managed soils allows for much more wind movement.”
Stiefvater, for one, doesn’t think it will. “They saw this storm as one freak event. I don’t think they comprehend how much soil they are losing,” he says. When he learns of the NRCS estimates of soil loss in May, Stiefvater wonders aloud: How much top soil, the very thing farmers try to maintain or build, did the region really lose and where did it go?
The Perfect Storm for Soil Erosion
Aside from the derecho, this spring has been much more windy and dusty throughout the Northern Plains than usual. “The winds have been ferocious. I can’t remember more days of 40-mph sustained winds,” says Anthony Bly, a soils field specialist for South Dakota State University Extension in Garretson, South Dakota.
“The wind events, with the drought widespread in the plains, are feeding on each other, because any wind on poorly-managed soils allows for much more wind movement,” says Dennis Todey, director of the Midwest Climate Hub in Ames, Iowa. The dry soil has played an often-overlooked role, he explains, by heating the air above the surface, which warms and adds to the turbulence. “The lack of soil moisture adds energy to the atmosphere, exacerbating the wind,” Todey adds.
Dust storms require high winds and emissive soil. But three things dictate how emissive the ground will be—how loose it is, how dry it is, and how much is growing in it—i.e., “vegetative cover,” says Jennie Bukowski, an environmental scientist at the University of California at Los Angeles who studies haboobs. In spring, vegetative cover is at an annual low, especially in regions where farmers till a lot. But as the drought persists in the West, crop residue—the layer of stalks, stubble, leaves, and seed pods left on the surface of the soil after harvest—isn’t holding up. “What keeps residue resilient is the moisture in it,” explains Backhaus. “With humidity in the single digits, residue tends to break down faster,” he says. “And without residue to hold the soil [down], it blows [away]. It’s this vicious cycle.”
Tillage also reduces residue and loosens soils, making it more prone to blowing away. Researchers compared wind erosion under different tillage regimes in North Dakota in 2003, a dry year with two months of less than 30 percent of average precipitation, and 2004, which saw more typical precipitation. They found that the residue-destroying effects of a single tillage event can be considerably exacerbated by a moderate, seasonal drought. Erosion was more than five times worse in 2003 than it was in 2004. Two field passes with disk tillage, a common practice to manage post-harvest crop residue in the fall, resulted in 5 tons/acre of soil loss compared to just under 1 ton/acre in no-till fields. “It doesn’t take much tillage to disturb that surface and cause it to go,” says study co-author, Ted Zobeck, a retired USDA erosion specialist based in Lubbock, Texas.
In addition, SDSU’s Bly is concerned that the enormity of modern equipment causes even more tillage-based degradation. “I really think we are wrecking the soil quicker than 30-40 years ago,” he says. A recent study—comparing farm vehicles to dinosaurs—backs up his experience. The total weight of combine harvesters has increased nearly 10-fold, from around 8800 pounds in 1958 to about 80,000 pounds in 2020. At a time when farmers are desperate to hold onto soil moisture, the subsequent compaction caused by all this weight can limit water infiltration, which is particularly troublesome when high intensity rains can’t be captured and stored in the soil.
In these regions, there is very little conservation tillage, says Bly. Stiefvater estimates that at most 15 to 20 percent of his neighbors use conservation practices. “It’s maximum tillage, and very little cover crops,” says Bly. Backhaus says in Colorado no-till acres have been on the rise, but farmers still have a long way to go. “In my mind, no-till should be on 100 percent of cropped acres,” he says.
A Wake-Up Call?
Backhaus was in Minnesota when the derecho went through the area. “That was a first,” says the Iowa native. “This isn’t Arizona,” he says. “That tells me that a lot of changes—especially to storm intensity and duration—are occurring and somehow or another we have to reverse [the trend toward soil loss] to get it back to something sustainable,” he says. “If we don’t store some more moisture, we won’t be able to produce the food that feeds the world.”
“We do have a choice. Are we going to rise to the occasion in terms of climate, water resource management, and good farming practices—or are we not?”
Stiefvater says he hasn’t seen much interest in conservation or regenerative farming practices in South Dakota. “There is no long-term planning, it’s just routine,” he says. “We gotta break the routine.”
As Steifvater was helping clean up homes impacted by the dust storm in town last month, he says old timers brought up the “Dirty Thirties,” a decade when dust storms were common and millions of acres of cropland could simply not be farmed. “They remember having to shove rags in windowsills so babies didn’t choke to death,” he says. “We don’t want to go back there.” He wants farmers to take the initiative rather than risk government having to step in. “We don’t have to do it all at once, but let’s start moving in that direction,” he says.
Maxwell Webster, Midwest policy manager for the American Farmland Trust, agrees. “We’re really starting to see impacts from climate and extreme weather accelerate,” he says. “As an organization, we’re trying to expand adoption of conservation practices in a short period of time to minimize soil losses.”
Climate change models predict more intense rainfall, when it occurs, and more frequent drought in the central and southern Plains in the near future. “Winter wheat farmers and rangelands will struggle [in the southern Plains],” says Webster. Changes that allow the land to soak up and hold moisture are key. “Part of the reason we focus on cover crops is to keep soil in place, and add organic matter back to help improve water retaining capacity,” says Webster. “It’s important for mitigating drought, but also mitigating the impacts of flooding,” he adds. Put simply: The aim is to keep water in crops rather than letting it wash into a drainage ditch.
Cover crop adoption, however, in most states hovers between 3 and 5 percent, says Webster. The USDA’s goal is to expand cover crops to 30 million acres by 2030, effectively doubling the amount in the ground currently.
Bukowski suggests farmers should adopt cover crops sooner rather than later, while it’s still an option. “At some point, we may not have enough precipitation for cover crops,” she says. “We do have a choice. Are we going to rise to the occasion in terms of climate, water resource management, and good farming practices—or are we not?” she asks.
There are encouraging signs that conservation incentives are having at least a modest effect. North Dakota, for example, had the most acres enrolled in the Pandemic Cover Crops Program (PCCP), a temporary USDA program that offered farmers receiving federal crop insurance $5 an acre to grow cover crops. In fact, several Plains states—Texas, Iowa, Nebraska, and Minnesota—also ranked high in PCCP acres. Perhaps the people conducting outreach in the Plains states did a better job of engaging farmers, but, Webster adds, “areas that have the highest soil health concerns are the areas where you see the highest level of conservation practice adoption.”
As a recent study demonstrated, soil erosion has been extreme—at a median historical erosion rate of roughly 2 mm per year, which is equivalent to 12 tons per acre—and continues today, despite conservation efforts. “The scale of current conservation practices is simply too small to meaningfully protect agriculture, soil health, and water quality from the damages of extreme weather,” says Webster.
One hurdle, however, is that NRCS doesn’t have the bandwidth to assist even close to the number of growers who need it. “Right now, we’re short staffed,” says Backhaus. “We’re trying to build staff back up, then we can educate them to provide technical assistance to producers.” And, he adds, producers like to work with a single person, and build a rapport, which is another challenge given staffing shortages. There is also way more demand for federal conservation programs that support improved practices—such as Conservation Stewardship Program and Environmental Quality Incentives Program—than the funding allows for, says Jessica Michalski, South Dakota NRCS State Resource Conservationist.
But the amount of soil that blows into the air in the spring is also lost money down the line—in the form of additional fertilizer needed to offset losses, seed, and yield potential when topsoil is lost. “It’s easy to think about short-term economics when farming, it’s much more difficult to think about the long-term impacts to the land,” she says.
But, Michalski hopes to see more farmers “take first step and admit that you need to make a change.”
August 1, 2022
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