“Erosion rates have come down dramatically” since the 1980s, says Gary Sands, a University of Minnesota Extension biosystems engineer.

The USDA’s 2007 National Resources Inventory found that wind and water erosion on cropland decreased 43% between 1982 and 2007. Sheet and rill erosion dropped from 1.68 billion tons/year to 960 million tons/year.

That’s confirmed by a June 2010 report from the Natural Resources Conservation Service (NRCS). The Cropland Effects Assessment Project in the Upper Mississippi River Basin, or CEAP, estimates that conservation practices have reduced surface-water flow from cultivated farm fields by 16%, and cut sediment loss by 69%.

Reducing soil erosion and sediment loss has made a significant difference in water quality, says Don Baloun, the NRCS Minnesota state conservationist. Conservation practices have reduced in-stream sediment loads by 37%, P loads by 40% and atrazine loads by 51%, CEAP models show at the outlet of the Upper Mississippi River Basin at Grafton, IL.

 One of the main reasons for these improvements is the CRP, McIsaac notes. “A lot of those contracts are expiring, and if crop prices stay high, there will be an incentive for farmers to plow up grasslands, which will likely contribute to more erosion.”