Cruse: Iowa has lost 6.8 inches of topsoil, a $1 billion-a-year economic hit
Rick Cruse, an Iowa State University agronomy professor who directs the Iowa Water Center, said new calculations show that Iowa has lost 6.8 inches of topsoil to erosion since 1850.
That means a $1 billion annual hit to the economy based on lost crop yields, Cruse added.
The findings come as Iowa debates how to reduce runoff pollution, which has led to health advisories at state park swimming beaches and a federal lawsuit over nitrate contamination in the Central Iowa water supply.
That is worse than previous estimates because previous models didn’t take into account all types of erosion, including the gully washers that come after a large rain, Cruse said.
Farmers can’t keep soil in place by growing only corn and soybeans, no matter how many conservation practices they use, Cruse wrote in an article in the Leopold Letter, a publication of the ISU-based Leopold Center for Sustainable Agriculture.
Cruse is part of a coalition of university and government researchers that now are using more detailed images of Iowa’s slopes, soils and rain.
That soil loss means a yield loss of at least 10 bushels per acre, Cruse estimated. “If you look at those figures and the amount of corn acres in Iowa, you quickly surpass a billion dollars of annual lost revenue,” he said. “And this is a very conservative estimate.”
Soil forms at a rate of a half-ton per acre per year, Cruse said. But federal agencies consider losses of 5 tons per acre per year acceptable.
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