In the US Midwest, agricultural practices have resulted in a loss of 57.6 billion tonnes of soil

In the US Midwest, agricultural practices have resulted in a loss of 57.6 billion tonnes of soil ...

A new study in the journalEarths Futureled by the University of Massachusetts Amherst shows that, since an Euro-American settlement, agricultural fields in the midwestern United States have lost, on average, two millimeters of soil per year. This is about twice the rate of erosion USDA considers to be viable. Finally, the authors conclude that plowing, rather than the work of wind and water, is the primary culprit.

Isaac Larsen, a UMass Geosciences professor and one of the papers co-authors, said that a few years back, my wife and I were at a wedding at a pioneer Norwegian church in Minnesota. I walked over to the edge of the churchyard, which was surrounded by cornfields, and was shocked to see that the surface of the field was a few feet below the surface of the never-tilled churchyard. I began to wonder why.

Larsen, along with the co-lead authors who completed the research as part of his doctorate at UMass Amherst, andJeffrey Kwang, a postdoctoral researcher at UMass Amherst at the time of the study, found himself standing in central Iowa on the edge of a native prairie.

Thaler had worked extensively with the Iowa Natural Heritage Foundation and other organizations to pinpoint the remaining areas of original, never-farmed prairie. He then reached out to farmers who abutted the prairies, asking them to land their own research. He found twenty sites in central Iowa, with some in Illinois, Minnesota, South Dakota, Kansas, and Nebraska. I spent a day driving around the Midwest, knocking on doors. I was convinced that no one was to blame when I arrived in person.

Thaler, who uses a sophisticated GPS receiver that looks more like a floor lamp than a hand-held device, crossed dozens of transects or perpendicular routes across the escarpment, from the unspoiled prairie to the damaged farm field, stopping every few inches to measure the elevation changes. Thousands of times during the summers of 2017, 2018 and 2019.

In response to the Dust Bowl in the 1930s, the team discovered that Midwestern topsoil is eroding at an average rate of 1.9 millimeters per year. And this is despite conservative methods used in the region.

However, the majority of erosion is due to tillageto plowing. According to Kwang, the methodology that I do shows that tilling has a diffusive effect. It melts the landscape away, flattening higher points in a field, and filling in the hollows. Although the USDA does not explicitly include such tillage erosion in its own analysis, it has significantly underestimated the rate of erosion currently at work in the heartland.

As erosion degrades our soils, it decreases our ability to grow food, according to Larsen. Combine this with increasing global population and climate stress, and we have a real problem. The team believes that greater sustainable farming and soil regeneration will likely be required to reduce soil erosion rates in the Midwest to levels that can sustain soil productivity, ecosystem services, and long-term prosperity.

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