To Salt or not to Salt
All too often in our wonderful winter wonderland, we are confronted with the need to treat the ice around us. Salts can be very useful to improve our safety, but that comes at a cost to our landscape plants and our waterways. Sodium harms plants directly and indirectly adversely affects soil quality. Salts also damage concrete, especially concrete poured in the past year.
“Rock salt” is sodium chloride, the same as in your table salt. It is the least expensive and most widely available. When spread on ice, it starts to pull water molecules from the surface of the ice and breaks down into separate sodium and chloride ions which forms a brine and continues to pull water from the ice. If this salty water is sprayed onto nearby plants (think snowplow), it can directly damage them by pulling water from the plant tissues. Water evaporates from the brine leaving behind the salt (think sea salt). Rock salt is ineffective below 15oF, so there is no point in using it in extremely cold weather.
The sodium eventually enters the soil. During the growing season, sodium competes with magnesium, calcium, and phosphorous that plants need to grow. Sodium also binds to clay particles and causes them to swell and bind together making soil less able to allow needed water and oxygen to penetrate to the roots. The only way to remedy “sodification” of soil is by the copious application of water to dilute and rinse it away.
Chloride has immediate effects of speeding corrosion of metals (bridges and automobiles) but does not remain in soil long term. Instead, chloride leaches into water where it remains. There is no affordable way to remove it from contaminated water and it just has to be eventually carried out to the ocean. Our favorite Great Lake take 99 years to completely refill with fresh water, and prior to the use of road salt its chloride level was 1mg/liter. As a result of salt use, the chloride levels in Lake Michigan rose from 9mgL in 1980 to 15mg/L in 2021. Although these levels are far below what we can taste or harm us, it is a different story for fish and plants in our rivers and smaller ponds where chloride levels can be much higher in the winter and spring and where it can be lethal to them. One teaspoon of salt contaminates 5 gallons of water.
Calcium chloride is often touted as a good alternative, but it has some unique problems. First off, it is 5 to 10 times as costly as sodium chloride. Second, it requires roughly twice as much to be as effective as salt. Thirdly, it can harm fabrics (carpets) and floors more than sodium chloride and can leave an unpleasant slick/moist feeling on some surfaces. Although the calcium can benefit plants, it still contains a lot of chloride.
All of the compounds that contain chloride are corrosive to metal and concrete.
The acetate containing products, in addition to being expensive, can cause algae blooms in water bodies which cause fish kills and smelly anaerobic conditions.
Traction agents like sand and non-clumping kitty litter are attractive, because they don’t harm other materials and are non-reactive to soils and not harmful to plants. However, if additional snow or ice falls on top of them they become encapsulated and ineffective. Also, they need to be collected and disposed of after the ice melts or they will accumulate in and block drains.
So, what are the best practices to minimize the effects of ice fighting agents?
- Shovel or blow snow offbefore compacting it by walking or driving on it. Compressed snow becomes ice. Please be a good neighbor and clear your sidewalks along with your driveway, and if you have a service make sure your sidewalks are included.
- Consider making a brine and spraying it on before an icy snowstorm. This reduces the amount you need to use and prevents the ice from sticking in the first place. This is what Riverside Public works is doing on our roads to reduce salt use.
- Use as little as possible. Don’t salt areas you don’t use in the winter. Spread it out thinly. Consider salting only the center of a sidewalk and letting it work its way outward which at least avoids getting salt directly on plants. Clumped up salt does nothing. Sweep up and re-use salt that does not melt. Letting rain wash away unneeded salt just harms your landscape and wastes your money.
- Avoid planting close to driveways, roadways, and sidewalks where salt spray is likely. Or consider planting salt tolerant plants – remembering that Riverside parkways and setbacks should only contain native midwestern plants (a permit is required).
- Consider adding traction to yourself with devices like YakTrax, IceTrax, Stabilicers or some other form of ice cleats. These work even if your neighbor hasn’t gotten around to clearing their ice yet.
- If repaving your driveway, consider pavers or other “permeable” solutions which reduces winter icing and decrease runoff flooding in the other parts of the year.
Making a Brine
Illinois mandates reduced road salt use.
Salt effects on Landscapes
Excellent source for salt tolerant plants and alternative agents
Alternatives to Sodium Chloride