New research finds massive soil loss across the Midwest, which sends more pollutants into the water, dust into the air, and carbon into the atmosphere. Changing farm practices and improved technology could reverse the trend
Chances are, if you live in North America, you’ve eaten corn from the Corn Belt, a region in the Midwest that produces 75 percent of U.S. corn.
Scientists have found that around 35 percent of the region has lost its most fertile A-horizon soil, more commonly known as topsoil, since European colonization in the 1600s, resulting in estimated annual economic losses of around $2.8 billion and a 6 percent reduction in crop yields per year. Their findings are published in the Proceedings of the National Academy of Sciences.
Farmlands with losses of topsoil require inputs of industrial fertilizers, which come at a cost to both farmers and the environment.
Using satellites, the researchers were able to compare the color of bare agricultural lands to make estimates about soil loss. This was the first study to use satellites and lidar (a radar-like system that uses lasers instead of radio waves) to estimate the relationship between soil loss and the land’s topography. The estimates were verified using a database of soil samples collected throughout the region, including in places that have never been farmed or plowed, such as native prairies.
Hilltops, they found, are often completely denuded of topsoil, while soil tended to collect in lower-lying areas. Soil loss is due mainly to erosion from flowing water.
Modern industrial agricultural practices are to blame for this exodus of dirt, in particular tilling, or plowing, said lead author Evan Thaler, from the Department of Geosciences at the University of Massachusetts, Amherst.
The mechanization of plowing began in the mid-1900s. While this allowed farmers to work larger areas of land, it has resulted in some negative effects on soil health. Tillage breaks up the soil and unlocks nutrients, but over time, the process compacts the soil and damages the microbial life important for capturing carbon and storing nutrients.
Thus, farmlands with losses of topsoil require inputs of industrial fertilizers, which come at a cost to both farmers and the environment. Farmers may spend hundreds of thousands of dollars a year on fertilizers. But due to erosion, much of this fertilizer simply washes away into watersheds and, in the case of the corn belt, into the Mississippi River.
“A third of the Midwest is currently losing 50 percent of its fertilizer,” Bruno Basso, a professor at Michigan State University, who was not involved in the study, said. “Which means the plants are stunted and smaller. And it doesn’t matter how much fertilizer you put on these areas, they will not take the nitrogen up. So, it’s a vicious cycle.”
Wasted fertilizers and stunted crops are costly, but the other cost is to the climate. Globally, more carbon is stored in the soil than in all the Earth’s plants and the atmosphere combined. When soil is left bare and washes away, important stores of carbon can be released into the atmosphere, worsening the climate crisis.
Addressing these issues will require a suite of solutions, Thaler said, including moving toward regenerative agricultural practices such as no-till farming and the use of cover crops (long used by Indigenous people and small farms) and the use of technology to optimize land management
One promising front, Basso said, is in the realm of digital agriculture, or “using digital and geospatial technologies to monitor, assess, and manage land.” Using tools like drones and satellites to monitor the productivity of their land over time, farmers can assess which areas are producing high yields and which parts (such as hilltops) are simply washing away.
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