The most common material used to melt ice is unrefined rock salt, which is about 98.5 percent sodium chloride -- the same chemical compound used as table salt, rock salt and an ingredient in water softeners.
This chemical can injure plants if too much is applied, Nuss says. Sodium can cause soil to become compacted, inhibiting root growth. A high amount of salt will block nutrients needed by plants and absorbs water, causing drought-like conditions. Sodium and chloride ions can be taken up by plants and can injure leaf margins and the tips of new shoots. Salty water splashed on plants can damage buds, twigs and new leaves.
The Park Maintenance Division of the U.S. Department of Interior considers the maximum safe application per season to be one-half pound of salt per square yard, Nuss advises.
Alternatives to rock salt
Used sparingly, garden fertilizer can be a safe alternative for melting ice. In a complete fertilizer, such as 5-10-10, muriate of potash (KC1) is the ice melter. The superphosphate adds traction, Nuss says.
"Fertilizer is not quite as effective as salt for melting ice, but it is beneficial to plants if applied in about the same quantities recommended for sodium compounds," Nuss says. "Applying too much fertilizer also can harm plants."
Pure nitrogen fertilizer, such as urea, also can be used. It melts ice at temperatures as low as 11 degrees F, and is best applied at temperatures between 25 and 30 degrees. Urea can be applied at a rate of 10 pounds per 100 square feet. For small areas, a mixture of 3 pounds of urea and 100 pounds of sand works well, Nuss says.
Calcium chloride is a more effective ice melter than fertilizer, but it, too, can harm plants. "Mixing calcium chloride with sawdust, however, will keep most of it from leaving the sidewalk in runoff water," Nuss says. "Apply one part calcium chloride to three parts sawdust. This provides traction, and when warmer weather comes, you can sweep up the mixture and either compost it or dispose of it in the garbage."
Other materials that can be used for traction are gravel, sand, cat litter or cinders.
One more thing -- if you decide to use fertilizer, sawdust or any of these materials that provide traction, keep a sturdy mat at your front door to prevent them from being tracked into your house.
