Prairie STRIPS Reduce Farm Nutrient Runoff by 90%

Date: April 14, 2014                                                                by Kristin Peterson

Above: Visual improvement in water quality from prairie STRIPS has been dramatic

Prairies once covered millions of acres in the central United States.  In the early 1900’s, with a growing population and the advent of agricultural mechanization, most of these prairies were plowed up and converted to farmland.

What if, by restoring small strips of this natural prairie, water quality and the environment could be improved?

Iowa State University’s Prairie STRIPS project, Science-based Trials of Rowcrops Integrated with Prairie, is studying what impact strategically placed prairie strips, composed of grasses and forbs, can have on water quality and quantity. The project also looks at benefits to bird, plant and insect diversity.  Prairie is planted in 10 to 30 foot wide strips along sloped fields of 6-10%, following the contour of the slope.

Above: What Prairie STRIPS can do

“What we are trying to do is try to figure out how, within the rural landscape, we can provide greater environmental benefits,” said Iowa State’s Matt Helmers, Associate Professor of Agriculture and Biosystems Engineering.

The STRIPS project compared four different practices: all row crops; 90% row crops and 10% prairie strips placed at the bottom of the slope; 90% row crops and 10% prairie strips planted in multiple strips across the slope; and 80% cropland and 20% prairie strips planted in multiple strips across the slope.

Replicated trials studies done in a watershed in Jasper County, Iowa have shown dramatic results. There, small portions of farm fields (10%) planted to prairie have shown a 95% reduction in sediment leaving the fields. In addition, there was a 90% reduction of phosphorus, a 90% reduction of nitrogen and a noticeable increase in bird and plant species in the area.  The stiff stems and deep roots of the prairie grasses are key.  Additionally, adjacent cropland fields did not report yield losses.

“By promoting the diversity of the plants in the watershed, we are reaping the benefits of that diversity in terms of improved soil, water and nature conservation,” said Matt Liebman.

Impressed with the results, CenUSA Bioenergy is taking the concept to an even larger landscape, the Mississippi River Watershed. CenUSA researchers are using modeling to evaluate the impact of planting perennial grasses strategically into cropland throughout the Mississippi River Watershed. Re-integrating perennial grasses into the Midwest landscape could provide dramatic reductions to farm nutrient runoff that is now leaking into the water and causing the Gulf of Mexico’s hypoxic zone, the second largest dead zone in the world.

To better address nutrient runoff to the Gulf, USEPA is now asking Midwest states to reduce their nutrient loading by 45%. At $40 per treated acre, STRIPS may be one of the least expensive in-field management practices available to help reach that goal. The STRIPS program has been running trials since 2007 and the results have been extremely consistent. The next phase is moving to more commercial farms.

“We think STRIPS is a viable approach for improving conservation and we’re taking it out to commercial farms across Iowa,” Liebman said. “We are not just giving a single, technical fix. We are providing habitat for wildlife as well as seeking to have a big effect on soil and water conservation.”

For more information see: http://www.nrem.iastate.edu/research/STRIPs/