I’ve used dolomitic limestone in place of salt, since I remember that it can add traction, but isn’t as toxic as salt around gardens on ice.
Should I worry about the ph at all, or will it be greatly diluted during the winter with snow and melted ice?
Although spring warming will take care of most of the ice, how do I determine the quality of the limestone product I’m buying? What do I look for to make sure the product is ok as the winter substitute for salt?
What’s attractive is that the price seems almost comparable to salt. Any difference is the coincidental amendment of soil during the off-season.
Interesting question! You are right, dolomitic limestone is a more ecological friendly de-icer than Rock Salt (Sodium Chloride), if used with care. It is less effective than rock salt at melting the ice, however if you buy it in a coarse, granular form, it last longer in wet conditions, providing traction for longer.
Dolomitic limestone is made from ground up dolomite, a type of limestone, and is a source of magnesium and calcium (both alkaline minerals). It is also used a pH buffer. This means it neutralizes acids in soil over time. In water it maintains a fairly consistent pH level, because neither mineral are particularly soluble in fresh water. When used on sidewalks to de ice, its pH changing effects are minimal.
Interestingly, both minerals react in acid water and experiments have being conducted to see if limestone can reverse acidification of lakes and rivers due to acid rain. So far, results have been promising.
Although your garden might enjoy small doses of dolomitic limestone, heavier applications of the alkaline minerals can raise soil pH. If you don’t have acidic soils you could be degrading your soil over time with too much exposure to dolomitic limestone. Your soil structure can breakdown, becoming compacted, less able to drain, creating a hostile environment for worms and other useful soil inhabitants.
For the purpose of de icing, try to keep your dolomitic limestone on your hard surfaces and away from your garden. If, over several years, you notice a change in your soil structure, in the lower lying areas where your driveway or footpaths may drain, you can do a soil pH test to check.
When buying dolomitic limestone you can read the chemical composition on the package or search for it online, to determine the quality. Sometimes its hard to read the very small labels on the packaging. If so, check the website of your preferred products manufacturer online. They should provide a technical data sheet that allows you read a complete breakdown of the chemical constituents, ratios of each and any additives. Typically, you would expect to find a mixture containing 50% calcium carbonate (CaCO3) and 40% magnesium carbonate (MgCO3) and some other minerals.