Why is soil salinity of concern in arid and semi-arid regions?
In humid regions, soils typically contain little or no salt, and soil water is relatively low in salt-related dissolved ions. That’s because abundant rainfall (and, in some areas, abundant snowmelt) leaches any salt present in soil and transports salt-related ions downward, past the root zone. In arid and semi-arid regions, on the other hand, the concentration of salt-related ions in both water and soil tends to be moderate or relatively high. Water and soil salinity are higher in arid regions because of two factors: • The rate of chemical weathering of earth materials, such as soils, minerals, and rocks, is relatively high, resulting in the accumulation of various natural salts. • The rate at which water is lost to the atmosphere through evaporation from soils and transpiration by plants — processes collectively known as evapotranspiration — is relatively high. The rate of chemical weathering is higher for arid and semi-arid areas than for humid areas because the temperatures of air a
