Magnesium Chloride Stresses Roadside Trees, Colorado State University Research Finds

Applying magnesium chloride to non-paved roads as a means of dust suppression and road stabilization can stress and cause damage to nearby trees, according to recent research conducted by Colorado State University.

High concentrations of the substance were found in symptomatic trees within 20 feet of roads where magnesium chloride was used for dust suppression, said Betsy Goodrich, a graduate student in the Graduate Degree Program in Ecology at Colorado State. She conducted the study under the direction of Bill Jacobi in the Department of Bioagricultural Sciences and Pest Management.

The study examined 60 roadside plots on 15 non-paved roads in Larimer and Grand counties.

"We evaluated tree health, including surveying for disease and insect damage," Goodrich said. "The strongest factor to explain the decline in health of the trees was the magnesium chloride."

Researchers also visually surveyed more than 200 miles of 55 non-paved roads in Larimer and Grand counties, and found 80 percent to 90 percent of roadside vegetation appeared healthy or only mildly damaged. Trees were found to be the most dominant roadside species affected by magnesium chloride. More severely damaged trees were found downslope of the road.  

Water moves the magnesium chloride from the road into roadside soils, and trees absorb the magnesium chloride through the soil. The amount of magnesium chloride that was applied to the road was strongly related to the amount in the tree’s foliage.

The next steps for researchers:

– determine if there is a safe level of magnesium chloride to apply for dust suppression without damaging trees,

– determine how long it takes magnesium chloride to have an affect on trees, and

– partner with county agencies to determine best practices for its application.