Corn Belt expands northwest into marginal grassland, pinching perennial-crop biofuel hopes

High corn and soybean prices are driving conversion of grassland, some of it marginal, to cropland in the western Corn Belt, posing the threat of soil erosion and limiting the possibility for perennial bioenergy crops such as switchgrass, according to research recently published in the Proceedings of the National Academy of Sciences. (Map shows relative change from grassland in 2006 to corn or soybeans in 2011)

The researchers at South Dakota State University used land-cover data from the National Agricultural Statistics Service to analyze changes in the Dakotas, Minnesota, Iowa and Nebraska from 2006 to 2011. They found that 1.3 million acres had been converted from grass to crops. The Corn Belt is expanding northwest, and the last such shift came in "the 1920s and '30s, during rapid mechanization of U.S. agriculture," Bob Steever of Brownfield reports.

The conversion "was concentrated mostly in North Dakota and South Dakota, east of the Missouri River," Steever reports. Not only is much of the former grassland subject to erosion, it has "vulnerability to drought," the researchers write. The expansion is also "posing a threat to water- fowl breeding in the Prairie Pothole Region" (mainly in the eastern Dalotas, southwest Minnesota and north-central Iowa) and other wetlands. "Longer-term land cover trends from North Dakota and Iowa indicate that recent grassland conversion represents a persistent shift in land use rather than short-term variability in crop rotation patterns." (Read more) It appears likely to continue; today, the Department of Agriculture forecast record corn and soybean crops in 2013.

One way to follow up on this story would be to check with your local Farm Service Agency office about signups for the Conservation Reserve Program, which pays farmers not to till marginal land.