Planting strips of grass across slopes is a standard technique to control soil erosion. Usually, the strips are planted to cool-season grasses, and the practice is used randomly within a watershed, depending upon which farmers choose to adopt it.
Researchers at Iowa State University's (ISU) Leopold Center for Sustainable Agriculture are asking how it would affect erosion if the strips were applied more systematically, and if they were planted to native prairie grasses.
In a study, the scientists are planting strips of prairie grasses over 10% to 20% of the landscape. The study is being conducted on crop land in 14 small watersheds inside the Neal Smith Wildlife Refuge in Jasper County, Iowa.
The researchers are monitoring the amount of sediment leaving each watershed, and the early results are dramatic. From April 1 through June 30, 2008, watersheds with prairie grass strips lost an average of ½ ton of sediment per acre, compared to 8½ tons per acre in the other watersheds, which had no grass strips.
The scientists are using prairie grasses, rather than cool-season grasses such as brome, for several reasons, explains ISU ag and biosystems engineer Matt Helmers.
"Some prairie grasses are taller and stiffer-stemmed, so they stand up better during windstorms and over the winter,” Helmers says. "Prairie grasses also add diversity to the landscape, providing habitat for animals and serving as hosts for insects, including those that might be beneficial for crops. In the future, there's potential for them to also become a source of biomass for renewable fuels.”
Research is expected to continue for seven years. "If the results continue to be promising, strategically located prairie grass strips hopefully could be incorporated into future conservation programs,” says Helmers.
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