Irrigation is an ancient and important agricultural practice. Crop yields are higher under irrigation and less dependent on the effects of weather.
Irrigation inevitably leads to the salinization of soils and waters.
In many countries irrigated agriculture has caused environmental disturbances such as waterlogging, salinization, and depletion and pollution of water supplies. Concern is mounting about the sustainability of irrigated agriculture. Application of irrigation water results in the addition of soluble salts such as sodium, calcium, magnesium, potassium, sulfate, and chloride dissolved from geologic materials with which the waters have been in contact. Excessive soil salinity reduces yields by lowering plant stand and growth rate. Also, excess sodium under conditions of low salinity and especially high pH can promote slaking of aggregates, swelling and dispersion of soil clays, degrading soil structure and impeding water and root penetration.