Two Mississippi agencies are working together to determine if growing native plants along highway rights of way will reduce maintenance costs while maintaining visibility and safety.
The Mississippi Department of Transportation and Mississippi State University’s Forest and Wildlife Research Center have sown native plant seeds along Highway 25 in south Oktibbeha County. The research team hopes native plantings will help reduce mowing expenses for the transportation department while also protecting water quality, preventing soil erosion and improving habitat for birds and butterflies.
"The MDOT spends about $209 million each year to maintain Mississippi&squo;s highway system," said John Guyton, principal investigator and MSU associate Extension professor. "If we can reduce the amount of mowing and the spread of invasive plants, we can make roadside maintenance more cost-effective while also increasing the beauty of Mississippi’s rights of way."
An expected 20 percent reduction in the amount of mowing needed each year could save taxpayers more than $10 per acre. In fiscal year 2009, MDOT employees mowed 298,808 right-of-way acres.
A survey of plants along the highway revealed that about 75 percent of the species are native to Mississippi. Despite the large number of native species growing in the state’s rights of way, introduced plants actually cover more ground. Introduced species include Bahia grass and Bermuda grass, which are useful for revegetating roadsides after construction projects.
"These grasses are economical and grow quickly to prevent soil erosion and protect water quality," said Dave Thompson, MDOT roadside development manager. "However, introduced species rapidly take over an area by outcompeting natives. Johnsongrass, for example, has a chemical compound in its roots that interferes with the growth of other plants."
Jeanne Jones, coinvestigator of the project and wildlife ecology and management professor, said mowing once a year in late fall—instead of mowing twice a year—would allow native species to reach maturity and release their seeds.
"Allowing native plants to flourish would also be beneficial for wildlife, as it would improve seed abundance for birds and other small animals," Jones said.
The research team has planted 10 plots with native plants. Five are in drier, upland areas, and five are in wetter, lowland areas.
While the experiment will provide an attractive display on the roadside, there is a concern that the abundance of vegetation and reduced mowing may attract deer and result in more collisions. Researchers set up trail cameras to monitor white-tailed deer and other wildlife in and around the research plots. They also are conducting ’spotlight surveys,‘ in which the researchers use high-beam lights at night to spot and count deer.
To discourage deer and other wildlife on the roadside, researchers planted less palatable native grasses and wildflowers. They planted other native plants that do attract deer in wet areas away from roads to reduce the risk of vehicle collisions.
"The results of the study will add to MDOT’s information base and provide useful data and potential options for best managing vegetation along Mississippi’s roadways," Thompson said. "The project demonstrates how MDOT must often balance competing interests, in this case promoting native species and protecting water and soil quality while maintaining driver visibility and safety."
The project will be completed in a year, but the benefits of native vegetation on the roadways will be lasting.