Archive for January 30, 2008

Melting the ice

This is information compiled by Linn County Master Gardener Darrell Hennessey about a question frequently asked the Horticulture Hotline, regarding environmentally friendly alternatives to using salt for melting ice:
 Most deicing compounds are salts that melt the ice on our roads and sidewalks by reducing the melting point of water below 32’F.  Unfortunately they can damage metal, concrete and plants.  There are other alternatives to consider along with their relative merits and limitations:
 Sodium chloride (NaCl)—this is the more common table or rock salt.  It is one of the more readily available compounds and is least expensive.  However, we’re all familiar with the corrosive effects salt can have as well as damage to plants and soil.
 Calcium chloride (CaCl2)—this compound does not leave the white residue on floors and carpets that NaCl does, but it’s also highly corrosive to concrete and metals.  It’s only slightly less damaging to plants than common salt.  It is effective to about -20’F.
 Magnesium chloride (MgCl2)—effective down to about +5’F, and it doesn’t leave the powdery residue.
 All of these salts can damage landscape plants when used to excess.  High levels of salts can accumulate in the soil with the result that water uptake by plants is inhibited and either we count on heavy spring rains or manual flushing from the root zone to limit the effects.  High levels of salt restrict the uptake of essential nutrients by plant roots.  Salt deposited directly on plant foliage can result in dehydration of the plant tissue.
 Some alternative to consider:
             * Avoid using salt entirely (use coarse sand).
             * Reduce the effects by pre-wetting with a salt brine.  An abrasive such as 50 lbs. of sand, cinders or ash mixed with 1 lb. of salt can be an acceptable compromise.
            * Place a barrier between driveways and walkways and susceptible plants.
            * When all else fails, use plants sufficiently tolerant of exposure to salt.  The Extension office has a list of plants with varying susceptibilities.
 
Master Gardeners are available to answer horticulture questions in an unbiased, research-based manner as a free service to the community at (319) 447-0647.
 

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