A 120-foot-wide ribbon of deep-rooted switchgrass spools along the Yellow Medicine River, a meandering prairie stream that winds through Doug Albin’s Minnesota farm. For decades, this stream-side grass strip has filtered out pollutants in surface runoff from adjacent cropland.

Recently, this buffer’s filtering power got a boost from a new conservation method, called a saturated buffer. The practice diverts subsurface drainage water into the buffer zone through shallow tile. “It works like a giant soaker hose,” says Mark Dittrich, a drainage expert at the Minnesota Department of Agriculture. “The water seeps out of the tile and raises the water table nearly to the surface.” As the nutrient-laden water percolates through the soil, it is denitrified or absorbed by plants.

Albin, of Clarkfield, Minn., is one of 15 Midwest farmers who are testing this new concept. (See his “platinum” conservation drainage plan, Page 8.) The $553,000, multi-state research and demonstration project is sponsored by the NRCS, the Farm Service Agency, and the Agricultural Drainage Management Coalition (ADMC), an industry consortium.

“There are tens of thousands of miles of grass buffers already installed along creeks and ditches” in the Corn Belt, says agricultural engineer and Project Manager Nathan Utt, Ecosystem Services Exchange, Adair, Iowa. “We’re looking at ways to enhance the effectiveness of these existing buffers.”

Last season, saturated buffers were installed on 15 farms in Minnesota, Iowa, Illinois and Indiana — all retrofitted to existing tile systems and grass buffers. The demonstration sites have different topography, drainage designs, soils, cropping systems and buffer characteristics. Researchers are collecting data on flow, N and P in the drainage water, soil conditions and stream bank movement.

“We want to see how this works across different landscapes, soils and climates,” Utt says.