20 - Chemical Injury

Abstract

A large number of chemicals used by human being are toxic to plants. This chapter discusses the most common groups of chemicals that are toxic to trees: deicing compounds, chemicals that cause spray injury, herbicides, and gases from underground pipes. Sodium chloride (NaCl) and calcium chloride (CaCl 2 ) are the two most commonly used chemicals to melt ice and snow on sidewalks, driveways, and highways. Both of these chemicals are sometimes applied together. The exact effects of deicing salts in the soil on roots are complex, but the salts are known to make water and essential nutrients difficult to absorb by the roots. Nutrient balance in the plant can also be affected by salt in the soil. The high concentration of sodium in salt-contaminated soil makes potassium less available to the roots. Salt spray is injurious to the foliage, twigs, and buds of trees and shrubs. The symptoms caused by salt injury are varied because of the different ways by which the salt reaches plants and the different responses of plants to salt stress.