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Keeping sidewalks and driveways clear from snow and ice is an important public safety issue. There are many 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 which 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 runoff. 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 probably the most widely used de-icing material. It is inexpensive but is damaging to plants and soils. It can also cause pitting on concrete surfaces.
• Calcium chloride and magnesium chloride are common replacements for sodium chloride. They are both somewhat less damaging to plants but are highly corrosive to concrete surfaces. They are hygroscopic (attract moisture), can cause a slippery film and may cause skin and eye irritations.
• Calcium magnesium acetate (CMA) has been created as an environmentally friendlier alternative to sodium chloride. It is safer for plants and not as corrosive to concrete surfaces. CMA can be up to 40 times more expensive than sodium chloride.
• Fertilizers have been boasted as being 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, too much of anything is a bad thing. Many fertilizers also contain iron, which stains concrete.
• Potassium chloride (0-0-60) or potash is a common fertilizer that causes less damage to plants but is highly corrosive to concrete surfaces. It is not as effective at lower temperatures and is often used in conjunction with other de-icing compounds.
• Urea (46-0-0), ammonium sulfate (21-0-0) and other nitrogen salts are rarely approved as de-icing materials due to environmental concerns of nitrogen runoff and leaching into ground water.
While any of these compounds can be instrumental in keeping sidewalks and driveways clear, avoid problems by using them sparingly. There is still no chemical that can replace a good shovel and a little sweat.
For more information, see the USU fact sheet, on De-icing Compounds and Utah Landscapes.
