Salt Damage to Plants

Whenever excessive salts accumulate in the soil, they can have negative effects on the soil and the plants growing there. The term “salt” can be defined as any chemical compound formed by the reaction of an acid and a base. Salts come in all shapes, sizes, and colors. They can be large blocks like salt licks, rock salt, and pellets, or very fine granules, such as table salt. Most think of sodium chloride (NaCl) “table salt” when they think of a salt; but other salt compounds include calcium chloride (CaCl2) and potassium chloride (KCl.) In Maryland, salts come in contact with plants and soils primarily through the application of winter deicing products or inundation of sea water.

When sodium chloride dissolves in water, the sodium and chlorine ions separate. These individual ions can affect both soils and plants. In plants, the sodium ions absorb water, making it less available to the roots. This excess salinity hinders roots from withdrawing water from the surrounding soil, and the plants suffer drought-related stress and reduced growth rate, since plants must exert much more energy to obtain the water they require. Unlike sodium, chlorine ions are absorbed directly into the plant. Chlorine tends to accumulate in the leaves where it interferes with the plant’s ability to conduct the photosynthesis of energy from sunlight, further impacting the health of the plant.

Salt spray can have similar damaging impacts on plants, harming leaves, buds, and twigs. Excessive salts, particularly NaCl, can harm the soil. Sodium can bind with soil particles, making the more useful nutrients like calcium, phosphorus, and magnesium unavailable to plants. Sodium in the soil also plugs small pore spaces between particles, making the soil less porous. This results in poor water filtration through the soil and excessive runoff, often resulting in ponding of water or the loss of soil through erosion. Repeated mixing of sodium chloride in soils can cause soil particles to become platy and ridged, much like concrete. These degraded soils loose most of their fertility unless corrective actions are taken. Using salt as a weapon in warfare was fairly common throughout history. Warring factions mixed salt with soil to ruin an enemy’s crops in a process known as “salting the earth.”

The best way to avoid salt damage around your home is to abstain from using sodium chloride as a deicing agent. Chemicals such as calcium chloride, calcium acetate, and sand can melt ice or provide traction on these surfaces. Building or placing barriers around salt-sensitive plants is another way to mitigate the impact of salts. Sometimes salt application is unavoidable, as may be the case along a busy street. In these instances, having plants that are salt tolerant is a good idea. There is a lot of information available to ascertain a plant’s tolerance to saline conditions.

Article by Mike Kay, FCFCDB

Nature note for 2/12/22