Released Jan. 11, 2008

LOGAN, Utah -- Can you give me the cold, hard facts on chemical de-icers?

Answer by: JayDee Gunnell, Utah State University Extension Horticulture Agent, Davis County

The remnants of the past few snow storms, aside from the aching back and sore shoulders from shoveling, are sheets of dangerously slick ice. Keeping sidewalks and driveways clear is an important public safety issue. Chemical de-icing materials are used in abundance this time of year to counter Mother Nature’s cold sense of humor.

There are different formulations of de-icing compounds, but all are salt derivatives, which are not good additives for soil or landscape plants. These compounds can physically “burn” plants if they contact the leaves. Where drainage is a problem, these salts may also build up in the soil profile, competing with plants for water. If concentrations become high enough, the physical structure of the soil becomes unsuitable for plant life. That is why there is little to no vegetation in areas near the Great Salt Lake.

De-icing materials are successful in melting ice because they react with water in forming a brine solution that lowers the freezing point. In addition to adverse affects on soil and plant materials, de-icers can also damage concrete surfaces and add to environmental pollution through run-off. De-icing materials vary in their effectiveness in melting ice as well as their potential for damaging concrete. Consider this information as you choose and use de-icers.

• Sodium chloride (common rock salt) is the most widely used de-icing material. It is inexpensive and will melt ice to approximately 15 F. However, sodium chloride is damaging to plants and soils. It can also cause pitting on concrete surfaces.
• Potassium chloride (potash) is less damaging to plants but is highly corrosive to concrete surfaces. It is not as effective at lower temperatures (below 20F) and is often used in conjunction with other de-icing compounds.
• Calcium chloride and magnesium chloride are mined from naturally occurring brines, such as the Great Salt Lake. They both melt ice faster than sodium chloride and are effective to minus 20F. They are both somewhat less damaging to plants but are highly corrosive to concrete surfaces, can cause a slippery film and may cause skin and eye irritations.
• Calcium magnesium acetate (CMA) was created as an environmentally responsible alternative to sodium chloride. It is considered to be biodegradable, safer for plant material and non-corrosive to concrete surfaces. CMA is effective at melting ice to approximately 15F, but is 30 to 40 times more expensive than sodium chloride.
• Fertilizers are often touted as good de-icing materials since they, too, are salts. While it is true that fertilizers (used in the right amount) produce positive plant growth responses, much like everything else in life, too much of anything is a bad thing. Many fertilizers may also contain iron, which stains concrete.
• Ammonium sulfate (21-0-0) is a fertilizer often used as a de-icing material. It is not recommended as an ice-melt because it is highly corrosive to concrete. The sulfur in this fertilizer may benefit plant material, but it negatively reacts with the concrete in forming a mild acid that deteriorates the concrete’s surface.
• Urea (46-0-0) in its pure form is often used by airports because it is safest on runways as well as on the airplanes. Urea is effective at melting ice to 15F. However, agricultural grade urea is the most commonly sold form of urea fertilizer and is considered to be corrosive to concrete.

While these compounds can be instrumental in keeping sidewalks and driveways clear, avoid problems associated with these products by using them sparingly. There is still no chemical that can replace a good shovel and a little sweat.

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http://extension.usu.edu/htm/news/articleID=2397

Contact: Julene Reese, (435) 797-0810, julener@ext.usu.edu