Types of de-icers
Calcium chloride will continue to melt ice down to temperatures of 25 degrees below zero. It forms slippery, slimy surfaces on concrete and other hard surfaces. Excessive use can harm plant roots.
Sodium chloride (rock salt)
Sodium chloride is effective down to about 12 degrees. It can damage not only plants but also metals and soils. It is the cheapest option.
Potassium chloride is a naturally occurring material also used as a fertilizer and a food-salt substitute. It can melt ice when temperatures are in the teens. The high salt index can lead to serious plant injury.
Urea (carbonyl diamide)
This fertilizer is sometimes used to melt ice in temperatures as low as 21 degrees. Though less harmful to plants, urea can contaminate both ground and surface water supplies with nitrates.
Calcium magnesium acetate
CMA is made from dolomitic limestone and acetic acid (the principal compound of vinegar). The performance decreases below 20 degrees. CMA has little effect on plant growth or concrete surfaces, but is more costly.
Source: K-State Research & Extension
The blizzard that hit Lawrence over Christmas was a less-than-ideal opportunity for homeowners to test how much product it would take to melt down icy sidewalks and driveways.
But temperature, amount of ice and proximity of vegetation should be kept in mind before de-icing your property, according to Kansas State University Research and Extension.
“Some people think it doesn’t matter how much you use, you’re not going to have damage to your plants — but it is dose-specific,” says Ward Upham, a horticulturist for K-State Research and Extension. “The more you use, the more likely you are to damage your plants.”
Upham says people should only use de-icer when ice becomes difficult to remove with a snow shovel. It is important not to use too much de-icer because of its possible harm to plants and concrete.
“Anything that has roots can be affected by those salts,” he says.
While the salt can dry out plant roots, it can also cause pitting in concrete sidewalks and driveways.
The temperature can make a difference also, as most de-icers only work above a certain temperature. Calcium chloride, which is commonly used by homeowners, works to 25 degrees below zero, while rock salt, the cheapest and most commonly used by municipalities, only works to 12 degrees.
While rock salt and calcium chlorate can cause plant damage if overused, Upham says a newer form of de-icer, calcium magnesium acetate, is less harmful for the environment. However, it’s more expensive.
Upham also says contrary to some people’s beliefs, de-icer does not increase traction. More effective materials to increase traction are sand, cat litter or even cracked corn or bird seed.
“(De-icer) doesn’t increase traction; as a matter of fact, the calcium chlorite tends to make concrete a little bit slick,” he says.
According to a 2007 article from Jennifer Smith of the Douglas County Extension Agent-Horticulture for K-State Research & Extension, people need to keep the salt content in mind even after the ice and snow melts.
“Even if plants do not exhibit signs of salt injury, high levels of salt in the soil increase plant stress, making them more vulnerable to insect and disease problems,” Smith says. “Increasing organic matter content and watering by hand when the ground thaws will help to leach salt out of the soil and away from plant roots.”
Though Lawrence homeowners are required by the city to remove snow or ice within 48 hours of the end of a snowfall or ice accumulation, residents still need to keep in mind the chemicals and materials they are spreading on the ground.