Tom Philpott’s latest book, Perilous Bounty, was published Aug. 11. Photo by Gabriel C. Pérez
To see the Corn Belt in its full productive glory, your best bet is to visit in July. At the height of the summer growing season in an average year, you’ll see a show of force, a statement of industrial agriculture’s raw power. Crops are planted so tightly and grow so briskly that the region generates more photosynthetic activity than any other spot on Earth during July, a 2014 NASA analysis of satellite imagery found.
But to see the region when it’s vulnerable—to get the best sense of what could possibly go wrong with such a regimented system—you have to go in the spring, sometime between the first thaw and the end of planting. It’s like bumping into a champion heavyweight boxer at the hotel buffet at breakfast the morning after an epic brawl. In this spring interlude, the vast majority of ground is uncovered, save perhaps for stubble left over from the harvest. When the rain hits bare ground, soil begins to move.
Few people know more about the interaction of soil and water—and the sometimes-disastrous consequences that can ensue—than Rick Cruse, a professor of agronomy at Iowa State University. Cruse is the foremost authority on soil erosion in the Corn Belt. Since the early 1990s, he has run the Daily Erosion Project, which estimates soil loss in Iowa and surrounding states. He also runs the Iowa Water Center, a collaboration between Iowa State and the USGS to study the state’s water quality.
In early June 2019, I got Cruse to give me a tour of Iowa farmland around Ames in my rented Hyundai. He’s a tall, slender fellow with close-cropped graying hair and a longtime teacher’s gentle, patient way of explaining things. Normally by that time of year, I’d have been too late to catch the transitional lull in full display. The landscape’s annual green carpet would already be established. The corn would be at least knee-high, and the soybeans not far behind: another bin-busting harvest in its first blush of youth. Not that year.
During the second week of March, what meteorologists call a bomb-cyclone storm rampaged across the plains, bringing blizzards, heavy rains, and monster winds from Colorado to the Great Lakes. Bomb cyclones are fierce, hurricane-like events that form when a region of warm air meets one of cold air, causing a fast drop in barometric pressure. The storm system brought hard rain, which pelted the snow, melting it. Because the soil was still frozen from a long, cold winter, the water couldn’t percolate downward, as it would in warmer conditions, at least a little. So the resulting cascade moved to lower ground, triggering historic flooding.
But water wasn’t the only substance the March bomb cyclone pushed downhill. When a sheet of water moves across bare ground, it doesn’t percolate downward, but it does melt the top layer, turning into “mush,” Cruse told me. “If you step in it, it’s like walking on pudding.” Saturated with water, soil is prone to wash away.
The bomb cyclone on its own would have made for a remarkably destructive spring. “Baby calves were swept into freezing floodwaters, washing up dead along the banks of swollen rivers,” the New York Times reported from the ground in Nebraska that March. “Farm fields were now lakes.” Three people died, and in many places, “rail lines and roads that carry farmers’ crops to market were washed away by the rain-gorged rivers that drowned small towns,” the Times added.
But relentless rain continued through June, leaving nearly the entire Corn Belt a mud pit and delaying planting by at least a month. One farmer located just over the border in Illinois, Brian Corkhill, told me he had experienced “basically six weeks straight of rain” by early June, giving him only two days that were dry enough for planting the entire spring. By that time of year, he told me, he’s typically “long since done” sowing 1,300 acres of corn and soybeans. Under normal conditions, “corn would be knee-high or a little taller,” he said. Instead, in 2019 he didn’t even start planting until May 16, a day after he’s usually done. By the first week of June, he had just over half of his corn and none of his soybeans in the ground. Stories like Corkill’s resounded through the Corn Belt, from Nebraska to Ohio, Minnesota to Missouri. It was the region’s slowest and latest corn-planting season on record.
But it wasn’t the lateness of the planting and the disarray of the fields that Cruse was eager to show me when I caught up with him in June. Thanks to the Corn Belt’s overwhelmingly industrialized and technology-laden consolidation, the world has plenty of corn and soybeans, and a massive abundance of the foods derived from them: cheap meat, sweeteners, and fats. In the grand scheme of things, one year’s short corn and soybean harvest wouldn’t have a massive impact on a food system awash in those crops.
Rather, Cruse wanted to show me what the wet, wild spring meant for the region’s soil. As we rolled down two-lane highways at 60 miles per hour, we saw field after field of bare ground. Some of the plots had shoots of corn poking through; here and there, other patches were submerged in a foot or two of water, the aftermath of recent rains. The landscape’s dominant feature by far: mud.
This flagrant display of naked land emerged as a rite of spring in recent decades. But historically, it’s an anomaly. For millennia, the region was dominated by perennial prairie grasses and wildflowers, which plunged their roots deep into the ground and provided a thick stand of vegetation. When heavy spring rains hit, the roots below anchored the ground and the stalks above buffered it, holding soil in place despite the deluge. Moreover, the cycle of growth and decay of root mass and stalks provided a steady helping of organic carbon to the soil, feeding a vast web of microscopic organisms. In turn, these creatures recycled nutrients, making them available to the grasses for each spring’s new-growth surge. The grasses didn’t just protect the soil from the brute force of hard rain; they also provided a kind of sponge for rainwater to percolate downward, with the roots serving as channels. This percolation effect reduced the frequency of heavy floods and provided a store of water that could maintain plant growth during hot, dry summers.
That was then. Now we’re in the world of corn and soybeans, planted in the late spring and harvested in the fall, leaving the ground bare from November through the end of June, when the crop canopy is high and thick enough to protect it.
Every few minutes, Cruse slowed down to show me a sight that clearly pained him: large gashes that follow contours in farm fields, formed by water runoff during heavy rains. Known as “ephemeral gullies,” these channels represent soil that’s been carried off fields and dispersed into ditches and streams. They’re called “ephemeral” because when one forms in the spring, farmers typically till the ground and push fresh soil onto it to cover it over. But that stopgap solution makes the gullies prone to forming again the next year. They’re essentially pipelines, periodically filled by farmers, that remove millions of tons of topsoil from prime farmland.
Cruse explained that when he was a kid growing up on a farm in northeast Iowa in the 1960s, his father had a special name for the spring storms that occasionally raged through the region, dropping massive amounts of water over a short time. He called them “gully washers,” because of their tendency to expose these vulnerable regions in bare fields. One spring Sunday, a particularly savage storm blew through, and in its aftermath, the elder Cruse gathered the family in the sedan for a drive to survey the damage, calling out the names of farmers who had allowed huge swaths of their fields to be gouged away in the deluge. “My father told me something I’ll never forget: ‘Soils are connected to everything. Without soils we have nothing,’” Cruse told me. And he has been surveying the damage to Iowa’s fields from storms ever since, documenting and spreading the lessons he learned on that primal Sunday drive.
When we got back on the road, I asked Cruse to talk me through the math. Just how much soil is Iowa and the greater Corn Belt hemorrhaging, and what is the natural replacement rate?
The precise rate at which soil renews is hazy and difficult, varying by soil type and climate. In its reckoning, the U.S. Department of Agriculture assumes Iowa farms can lose up to 5 tons per acre of ground per year without trouble. The trouble, though, is that the USDA has never delivered solid science to back up the 5-ton assumption. In a 1998 paper, Cruse and a coauthor concluded that “seldom has such an important policy been based on such a dearth of defendable data.” And the research that has emerged since suggests that the so-called “soil-loss tolerance” rate is actually much lower. In fact, lower by an order of magnitude: around 0.5 tons per acre.
How much are Iowa’s farm’s losing? Cruse’s Daily Erosion Project delivers estimates of soil loss in Iowa and surrounding states based on frequently crunched rainfall data, topography, and farm practices. Over the decade, the DEP estimated, Iowa’s soil has eroded at an average rate of 5.4 tons per acre annually. There’s a catch, though. The data the DEP relies on can paint a reasonably accurate picture of sheet-and-rill erosion, but a precise way of reckoning for ephemeral gullies has proved elusive (though Cruse said his team was getting close). For the time being, the official calculations leave gullies out. However, Cruse’s best estimate, based on his own work and that of the research literature, is that ephemeral gullies claim an additional 3 tons per acre annually. Add that to the sheet-and-rill number, and you get an average of 8.4 tons of prime prairie soils washed away per acre per year. That suggests that Iowa—and much of the surrounding Corn Belt land—is losing soil at a rate nearly seventeen times the pace of natural replenishment. And these long-term averages, Cruse stressed, by definition undershoot the damage done during massive soil-loss years like 2019.
As I took that in, we stopped to gape at yet another ephemeral gully, a long, curving scar carved into the land, an abyss where some of the world’s best soil once grew crops. “Why?” Rick muttered, pained. “Most of the scenes we’ve seen in these fields are recurring, year after year after year.”
As Cruse and I headed back to Ames on that early-summer soil-damage tour in 2019, I asked him about a technology fix. Couldn’t, say, gene-edited crops engineered to shrug off drought bail us out?
He chuckled. “Formula One is a great technology, and when you put it on the Indianapolis Speedway, it does marvelous things. But on a dirt road behind the house, in a pasture? Same technology, but it just doesn’t perform.”
“You can’t make something from nothing,” he said. Food ultimately draws its nutrients from the soil, and degraded soils produce crops with lower levels of protein and other nutrients. The kinds of technology that can make a difference, he said, are practices that hold soil in place and build up its carbon content.
Failing that, I asked him, how long can we go on like we are? He thought for a second. “When you look at the averages of soil loss, they look bad, but it’s not the averages that get you—it’s the extremes,” he said. Climate change promises to keep visiting more and ever wilder spring tempests
upon the Corn Belt, more summer heat waves, more droughts.
He declined to predict how long the region’s farmers could continue wringing bumper crops out of this precious but dwindling cache of soil. But its vulnerabilities are already showing, and the ripple effects are scary. He pointed to the course of the Arab Spring pro-democracy movements in the early 2010s. The Arab Spring was triggered in large part by food riots; the explosive growth of crop-based biofuels, Wall Street speculation, and poor harvests in several drought-plagued growing regions across the globe had caused food prices to spike, squeezing urban population across the Middle East. Then the Corn Belt drought of 2012 slammed U.S. corn yields; since the United States supplies nearly 40 percent of the corn that trades globally, the losses reverberated through global markets, providing another turn of the screw just as the early hopes of the Arab Spring movements were fading.
Cruse said he expected more spring rains to sacrifice more soil, making the land ever-more
vulnerable to drought. “It’s a snowball running downhill,” he said. As we headed back to Ames, we gaped at several more ephemeral gullies, waiting to be refilled with some of the globe’s best soil and planted with corn.
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