Information On Chloride And Plant Growth
By: Jackie Rhoades
One of the most recent additions to the list of micronutrients is chloride. Though the condition is rare, the effects of too much or too little chloride on garden plants may mimic other, more common problems.
Effects of Chloride in Plants
Chloride in plants comes mostly from rainwater, sea spray, dust, and yes, air pollution. Fertilization and irrigation also contribute to chloride on garden soil.
Chloride is easily dissolved in water and enters the plant through soil and air. It is essential to the chemical reaction that allows the opening and closing of the plant’s stomata, tiny pores that allow gas and water to be exchanged between the plant and the air around it. Without this exchange, photosynthesis can’t occur. Sufficient chloride on garden plants may inhibit fungal infections.
Chloride deficiency symptoms include wilting due to restricted and highly branched root systems and leaf mottling. Chloride deficiency in members of the cabbage family is easily detected by the lack of cabbage odor, although research has yet to discover why.
Too much chloride on garden plants, such as those grown by the poolside, will result in the same symptoms as salt damage: leaf margins may be scorched, leaves will be smaller and thicker, and overall plant growth may be reduced.
Chloride Soil Test
Adverse effects of chloride and plant growth are rare because the element is so readily available through a wide variety of sources and excesses are easily leached away. General analyses rarely contain a chloride soil test as part of the typical panel, but most laboratories can assay for chloride if requested.
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Read more about Soil, Fixes & Fertilizers
You may not realise it but chlorine is classed as a plant micronutrient meaning that it is essential for the proper growth of plants. It is important to note though, that it is the ion (Cl ‑ ) rather than the gas (Cl2) that is used by plants. In particular, chlorine is important for plant photosynthesis as it is involved in the opening and closing of stomata (pores in leaves that enable plants to take in and release carbon dioxide, oxygen and other gases as required. It also helps ensure leaves are firm.
For your plants’ sake, go easy on the salt
Removing ice from roads and walkways in winter might be essential for safety, but salt can be damaging to plants and soil.
Salt has the same effect on plant roots as salty potato chips do on your lips: It draws water from living cells. Salt can ruin soil structure so it wads up into an airless mass. Not a nice place for plants to grow.
And damage from winter salt is sneaky, not manifesting itself until spring or later. Then, new leaves might emerge pale green or yellow or, later in the season, leaves may look scorched or turn their autumn colors early. Stems might die back or be stunted.
Older plants can sometimes recover from salt injury, especially if spring and summer rains are abundant.
Using less salt can help highway studies have found that, in de-icing roads, salt was effective in smaller amounts if sprayed as a brine rather than spread as crystals. Maybe it’s time to get out that garden sprayer again.
And you can leach out much of the salt by flushing the soil beneath a prized tree or shrub in spring with water -- using 1 gallon per square foot or a 2-inch depth over the course of a few hours.
Alternative salts -- those other than sodium chloride -- are another possibility. Calcium chloride is a frequently used alternative which, besides being less damaging to plants and soils than sodium chloride, also melts ice faster and is effective at temperatures well below zero degrees Fahrenheit. Sodium chloride, in contrast, loses some of its effectiveness at temperatures above 10 degrees Fahrenheit.
Still, calcium chloride does put chloride ion, which plants don’t like, into the soil, and it is more expensive and more corrosive to vehicles than sodium chloride.
Chemical (synthetic) fertilizers are all salts, so someone hit upon the idea of using them for de-icing. But besides being more expensive than either sodium chloride or calcium chloride, fertilizers such as potassium chloride or ammonium nitrate are most effective only at temperatures above about 20 degrees Fahrenheit.
Furthermore, ammonium nitrate is corrosive to concrete, and both compounds have a high “salt index,” so are apt to burn plants anyway in the amounts used for de-icing. Potassium chloride, of course, also can put excess chloride ion in the soil.
A popular, relatively new salt used for de-icing is calcium magnesium acetate, better known as CMA. Produced when limestone and vinegar are brought together, CMA eventually decomposes and is not damaging to plants or soils. It also sticks to the pavement better than salt and does not cause corrosion.
CMA does have shortcomings. It’s most effective above 15 degree Fahrenheit (about the same as rock salt). It’s slow to begin working. And it’s a lot more expensive than salt. CMA is better at preventing icing rather than getting rid of ice, so is best applied before ice forms.
Yet another de-icing method is to spread something other than salt on the ice gritty materials such as sawdust, unused kitty litter, wood ash or sand are effective. Still, nothing’s perfect. These materials track indoors unless you take or shake off your shoes at your front door.
ADOPT A HOLISTIC APPROACH
The best approach to ice is holistic. Use a combination of materials that takes into consideration both the traffic and the plants. If you sprinkle a preventive dusting on the ground before ice forms, you’ll need less salt for shoe and tire traction.
And if you’re planning some plantings along the road, driveway or walkway, choose from plants that tolerate salt. Besides plants native to seashores, other salt-tolerant trees and shrubs include silver maple, horsechestnut, honey and black locusts, poplar, junipers, mockorange, lilac, larch and Colorado blue spruce.
Ice Melters and Their Effects on Plants
Ice Melters and Their Effects on Plants
We are approaching the time when icy streets and sidewalks may again make walking and driving hazardous. Ice melting products can help keep us safe. However, these products vary in their ice melting abilities and in their safety to nearby plants. There are 5 main materials that are used as chemical de-icers: calcium chloride, sodium chloride (salt), potassium chloride, urea, and calcium magnesium acetate.
Calcium chloride is the traditional ice-melting product. Though it will melt ice to minus 25 degrees F, it will form slippery, slimy surfaces on concrete and other hard surfaces. Plants are not likely to be harmed unless excessive amounts are used. It is fast acting, and more effective than rock salt. Can damage grass and plants if overapplied.
Rock salt is sodium chloride and is the least expensive material available. It is effective to approximately 20 degrees F but can damage soils, plants and metals, and paving surfaces.
Magnesium chloride is effective down to minus 13 degrees F. and is more effective than sodium chloride. Can damage plants if overapplied.
Potassium chloride is effective down to 25 degrees F. and can also cause serious plant injury if overapplied.
Urea is a fertilizer that is sometimes used to melt ice. Though it is only about 10% as corrosive as sodium chloride, it can contaminate ground and surface water with nitrates. Urea is effective down to 10 degrees F., but works better between 25-30 degrees F. It can damage plants if overapplied.
Calcium magnesium acetate (CMA), a newer product, is made from dolomitic limestone and acetic acid (the principal compound of vinegar). CMA works differently than the other materials in that it does not form brine like salt but rather helps prevent snow particles from sticking to each other or the road surface. It has little effect on plant growth but can damage concrete surfaces. It is less corrosive than chloride products. Performance decreases below 20 degrees F.
Limited use of any of these products should cause little injury. Problems accumulate when they are used excessively and there is not adequate rainfall to wash or leach the material from the area. Since limited use is recommended, it is best to remove the ice and snow by hand when possible. When they are applied, practice moderation. We are often prone to over applying just to make sure the ice and snow melts. Keep in mind this can damage concrete surfaces as well as the plants and grass growing along the walks and driveways. These problems are normally latent and do not show up until spring or summer.
Salts can injure plants in several ways. The chloride ion is considered the most toxic element of deicing salts, causing much of the direct plant tissue damage. When salt sprays from puddles onto plants as cars drive by, it may scorch leaves or kill buds and twig tips on deciduous plants, especially during spring. Pines in general are especially noted for their sensitivity to roadside deicing salts. When affected, pine needles may become pale green, yellow, or brown in late winter. If dying vegetation is on the side of the plants facing the road or driveway, the damage has likely been caused by salt spray.
Accumulation of salt in the soil also makes it difficult for plant roots to absorb water. Excess sodium affects soil structure, and may result in poor infiltration and increased erosion. The sodium ions can displace essential plant nutrients, decreasing soil fertility. Salt accumulation in soil will also inhibit seed germination of grasses and wildflowers.
The level of damage varies, depending on the concentration of salts in the water running onto your plants, the amount of snowfall, the timing of rains that may help wash off the foliage, the type of soil, and the condition of the plants. Healthy, mature plants that are not drought-stressed will withstand salts better than newly established, young plants.
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