Tag Archives: ice

Roadside Turf That Tolerates Salt, Heat and Ice

A recently completed research study has identified turfgrass species and cultivars that perform best under the heat and salt on Minnesota roadsides.

Varieties from fifteen turfgrass species were tested in salt, heat and ice stress protocols. Analysis of color and cell membrane stability yielded recommendations for salt- and heat-resistant turfgrasses, but was inconclusive for ice-resistant cultivars. A mixture of cultivars was recommended for field study.

What Was the Need?

Minnesota’s roadside vegetation prevents erosion and keeps contaminants from reaching ground- and surface water. Turfgrass offers aesthetic value and unobstructed sightlines for drivers, but it must withstand harsh conditions.

Yellowing turfgrass in winter alongside Interstate 94.

In addition to year-round contaminants generated from highway traffic, Minnesota roadside grasses face snow, ice and salt from deicing operations in winter, and heat in summer that is even hotter alongside roadways and in urban environments.

Various turfgrass species may offer better resistance to specific stressors. Several current and recent MnDOT studies have evaluated salt tolerance and watering needs for select species of turfgrass. It was unclear, however, which species performed best under the multiple, combined stressors of Minnesota roadway environments, and would suit a mixture tailored to one of three Minnesota climate regions that could optimize turfgrass performance throughout the year.

What Was Our Goal?

This project sought to identify turfgrass species and cultivars that perform well under the range of stressors common to Minnesota roadsides. Successful cultivars may be candidates for turfgrass mixtures of multiple species that would optimize performance under all conditions in the field.

What Did We Do?

Researchers conducted a literature search to identify promising turfgrass species for harsh environments. Then they contacted seed companies for further recommendations before requesting seeds for multiple cultivars from 15 species. Next, researchers tested cultivars in salt, heat and ice stress protocols. Results from this testing are summarized below.

Salt Stress. The research team grew 38 individual cultivars hydroponically in 4-inch pots for 12 weeks. Then they suspended the pots in a salt solution for three weeks. Salt was added at the end of three weeks and again at three-week intervals at four salt concentration levels. Investigators compared digital images of green cover with in-pot color index meter results and tested cell membrane stability by measuring electrolyte leakage.

Heat Stress. Investigators grew eight samples each of 34 cultivars in 4-inch pots in a greenhouse for 12 weeks. Plants were trimmed manually to 2 inches. Half the plants were put through three heat stress cycles of 49 days of 95 degrees Fahrenheit and 70 percent humidity, followed by 28 days of normal conditions. Researchers then conducted digital imaging, in-pot color indexing and electrolyte leakage testing.

Ice Stress. After 10 weeks in a greenhouse, four samples each of 35 cultivars were placed in cold acclimation for 14 days at 35.6 degrees Fahrenheit. Investigators then moved pots to a chamber held at 28.4 degrees for 24 hours to freeze the soil, and then applied 2-inch layers of ice to each pot. A sample of each cultivar was removed at four, eight, 12 and 16 weeks, thawed for 48 hours in a 35.6 degree chamber and then moved to a greenhouse. Digital images were taken at 31 days in a greenhouse. A second batch was run as a control through the same trial up to the point of ice cover to identify if cold temperature was fatal to any samples.

A grid of 16 photographs shows green cover for four turfgrass cultivars: tall fescue, perennial ryegrass, Kentucky bluegrass and hard fescue. Increasing damage from salt exposure is shown for each cultivar after one, six, nine and 12 weeks.
A grid of 16 photographs shows green cover for four turfgrass cultivars: tall fescue, perennial ryegrass, Kentucky bluegrass and hard fescue. Increasing damage from salt exposure is shown for each cultivar after one, six, nine and 12 weeks.

What Did We Learn?

A mixture of turfgrass varieties and species will likely be the best solution for year-round use in Minnesota, as no one cultivar performed well in every trial.

Salt Stress. Tall fescue and perennial ryegrass sustained the highest percent green cover and lowest electrolyte leakage throughout the salt stress trials. Alkaligrass, considered salt tolerant, did not perform significantly better than other grasses. Only tall fescue emerged as a salt-resistant turfgrass option, though this cultivar is vulnerable to ice cover.

Heat Stress. Performance varied significantly within species, suggesting a potential for breeding improvements. Some species performed poorly under heat but recovered well when returned to normal conditions. Researchers recommended Canada and Kentucky bluegrasses, tall fescue, strong creeping red fescue and slender creeping red fescue as heat-resistant turfgrass cultivars.

Ice Stress. Tall fescue performed best in image and color analysis. Field observations and previous study, however, suggest that tall fescue performs poorly under ice cover. Warm season grasses died during the control cold storage. Researchers concluded that the ice trial did not properly simulate field ice cover conditions.

What’s Next?

The second phase of this study began in 2018 and employs a mixture of six species selected from this study: Kentucky bluegrass, slender creeping red fescue, hard fescue, buffalograss, alkaligrass and tall fescue. Mixtures will be planted in different combinations on roadsides for evaluation. MnDOT will also adjust its seed mixture recommendations for use in the meantime based on the results of this and other studies. Ultimately, MnDOT intends to develop recommendations tailored to three climate regions in Minnesota.

This post pertains to the LRRB-produced Report 2019-01, “Regional Optimization of Roadside Turfgrass Seed Mixtures,” published December 2018. For more information, visit MnDOT’s Office of Research & Innovation project page.

10 Ways Transportation Research Keeps Minnesotans Moving in the Winter

As the first big snow and ice storms sweep through parts of Minnesota today, we’d like to remind you of some of our great winter weather research studies. Here’s a list of some of this winter-related research from MnDOT and the Local Road Research Board:

Living snow fences

Living snow fences are trees, shrubs, native grasses, wildflowers, or rows of corn crops located along roads or around communities and farmsteads. These living barriers trap snow as it blows across fields, piling it up before it reaches a road, waterway, farmstead or community. Through multiple research efforts, MnDOT continues to advance its practices for living snow fences. Willow plants, which are which are inexpensive and fast-growing, are a new form of snow fence. MnDOT has also developed a tool that allows the agency to better offer a competitive payment to farmers.

Related studies:

Permeable pavement

According to recent studies, researchers believe Minnesota could eliminate salt usage on low-volume local roads by switching to permeable pavements. Permeable pavements — pavements that allow water to seep through them — have been studied in some Minnesota cities, and a research project is currently underway to further investigate how much salt reduction can be expected.

Related studies:

Traffic recovery during winter storms

MnDOT’s Metro District developed a way to automatically determine when to stop plowing a highway after a snow storm. The method involves measuring traffic flow to determine when road conditions have recovered. Current practice calls for maintenance workers to visually inspect traffic lanes. The automated technique could potentially be more accurate and save time and costs.

Related study:

Salt and other deicing chemicals

Minnesota winters are no joke, and Minnesotans still need to get wherever they’re going despite harsh snow and ice conditions. That’s why MnDOT is constantly researching new and improved versions of salt and other deicing chemicals to keep roads safe at the least amount of damage to lakes, rivers and groundwater.

Related studies:

Snowplow blades

A couple years ago, MnDOT snowplow operators in southwestern Minnesota invented an experimental plow that uses the wind to cast snow from the road without impeding traffic or the operator’s view. This winter, MnDOT intends to test multiple types of snowplow blades as part of a larger research project comparing types of deicers.

Related study:

Snowplow technology

While a lot of research has been done on the plow itself, MnDOT hasn’t forgotten to invest in research to improve in-cabin snowplow technology as well. Some of the great technology recently developed to assist snowplow drivers, includes a driver assist application that a MnDOT plow driver used last winter to navigate a storm and rescue stranded motorists. The agency is also studying equipment factors that can cause fatigue in snowplow operators.

Related studies:

Salt-resistant grasses

When the snow melts every spring, the damage salt does to roadside grass is obvious. That’s why researchers have spent years looking into developing and implementing salt-tolerant grasses on roadside settings. The result of this effort has been the introduction and use of salt-tolerant sod and seed mixtures that are made up primarily of fine fescue species. MnDOT is also studying how chlorides are transported within watersheds in order to better focus efforts to reduce deicer usage in  areas where it will have the biggest environmental impact.

Related studies:

Cold-weather cracking prediction test

MnDOT has developed a test that can tell whether a contractor’s proposed asphalt mix will cause the road to crack in the winter. Building roads using better asphalt mixes leads to less cracking and fewer potholes. The test is expected to save the state about $2 million per year.

Related studies:

Pedestrian snow removal

It’s not all about cars and trucks. Minnesotans still ride bikes and walk in the winter. That why MnDOT assembled a comprehensive review of existing practices and policies from other states, as well as a summary of valuable publications that could be referenced while developing a new policy.

Related study:

Maintenance Decision Making

MnDOT research led to the development of a Maintenance Decision Support System and related components provide real-time, route-specific information to snow plow drivers, as well as recommended salt application levels. These recommendations have reduced chemical usage while still achieving performance targets for snow and ice clearance.

Related studies: