Salinity

Soluble salt and exchangeable cation concentrations play major roles in determining the pH, physical characteristics, and chemical composition of soils. When a salt dissolves in water, it dissociates or separates into cations and anions. The predominant cations in salt-affected soils are calcium (Ca2+), magnesium Mg2+), sodium (Na+), and potassium (K+); the predominant anions are chloride (Cl-), sulfate (SO42-), carbonate (CO32-), and bicarbonate (HCO3-). Clays and organic matter contain negative electrical charge sites. In salt-affected soils, this charge is satisfied by calcium, magnesium, sodium, and potassium ions. These cations, bound to the exchange sites by the electrical charges, are known as exchangeable cations because they can be removed from the charged surface only by replacement with another cation from the soil solutio