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Cornell University : Cornell Cooperative Extension
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| Yates Association |
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Road Salt |
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Over the past 40 years, amounts of salt used for deicing roadways in winter have increased with greater traffic flow and growing concerns for public safety. Salt injures many plants growing along roadsides. Salt causes plants injury if it accumulates to excessive amounts in soil near the root system. Because salt readily absorbs water it absorbs much of the water that would normally be available to roots. Thus, even though soil moisture is plentiful, high amounts of salt can result in a drought-like environment for plants. When salt dissolves in water, sodium and chloride ions separate. Chloride ions are readily absorbed by the roots and they accumulate to toxic levels in the leaf margins and shoot tips. In leaves, this toxic build-up results in a characteristic marginal scorch. High amounts of sodium cause soil to lose its capacity to aggregate into clumps and it easily becomes compacted. Thus, access to water and oxygen is severely restricted and roots can't function to their full potential. Excessive sodium also restricts the uptake of magnesium and potassium, two chemicals that are essential for making chlorophyll. Potassium deficiencies, in particular, are common in plants suffering from salt injury. Salt that is sprayed onto plants directly can cause buds and small twigs to lose cold hardiness and are then more likely to be killed by freezing. In addition to the direct effects that salt has on plant growth, affected plants suffer reduced vigor and are more susceptible to attack by insect pests and diseases. Symptoms of excessive salt resemble those caused by drought or root injury. Stunted, yellow foliage, premature autumn leaf coloration, death of leaf margins (scorch), and twig dieback are common. One characteristic of salt injury that aids in diagnosis is that it is often confined to branches facing the road. Trees closer to the road suffer more damage than those set farther back. If salt were not used to deice roads in winter, salt damage to plants would be minimal. However the expense of this solution in terms of human life and safety precludes it. Thus, the problem is one of adapting to an undesirable but necessary circumstance. Sand, light gravel, or cinders are being used with increasing frequency in place of or in combination with salt to minimize plant injury. Late season applications (after March 1) are most detrimental to vegetation and should be kept to a minimum. Avoid piling salt and snow around plants or in places where the resulting salt water will drain into plants when the snow melts. If weather permits, it is a good idea to flush the area around roots exposed to salt with fresh tap or well water as soon as the snow melts. Where new trees are to be planted and where exposure to salt is likely, select species or cultivars resistant to salt injury. A list of salt tolerant plants hardy in New York State is available from Cooperative Extension. Tolerance varies with many factors, including exposure, soil texture and plant age. Cornell
Cooperative Extension Yates Association |
