KINGSTON, RI Erosion is a significant problem on highway embankments in New England. To mitigate erosion on the regions' highways, slopes are seeded with a grasslegume mixture that usually including red fescue, a grass preferred for its drought-tolerance and ability to thrive in acidic, infertile soil. "A mixture of red fescue, perennial ryegrass, and kentucky bluegrass is planted to stabilize the soil, but only the red fescue survives long term on slopes", noted Rebecca Nelson Brown, lead author of a report in HortScience. Brown and a team from the Department of Plant Sciences at the University of Rhode Island designed a study to identify alternative grass species that could help anchor slopes and prevent costly erosion.
Twenty-two grass species were included in the study conducted in the greenhouse at the Skogley Turf Research Center of the University of Rhode Island, and in additional roadside trials on the shoulder of a nearby state highway. Since federal highway policy strongly encourages the use of native vegetation in highway right-of-ways, the researchers tested grasses native to southern New England, comparing rooting depth, plant height, and adaptation to roadside conditions. Sixteen native grasses and five amenity grasses with red fescue were tested.
Roadside embankments are generally constructed of subsoil and gravel, over which 2 to 6 inches of topsoil is spread. The subsoils are very stony with coarse-textured loamy sand between the rocks; topsoil ranges from medium textured silt to sand. Red fescue is shallow-rooted with most of the root mass confined to the topsoil layer. When root growth is concentrated in a shallow mat with a sharp boundary in the soil profile, slope failure is likely to occur beneath the mat. Identifying alternative grasses that feature more even distribution of root mass with depth could help provide better slope stabilization.
Combined results of the greenhouse and roadside trials show
|Contact: Michael W. Neff|
American Society for Horticultural Science