ABSTRACT
Soil salinity is the oldest soil pollution problem. The collapse of the Babylonian Empire is considered to be partly the result of failure of irrigated crops due to the accumulation of salts. Soil salinity also occurs as a result of flooding by sea water. In 1953, extensive flooding occurred in parts of eastern England, Belgium and the Netherlands leaving large quantities of salt in the soil. The accumulated salts are present either dissolved in the soil solution in a moist soil, or as crystals in dry soil. Colour Plate shows massive crystals of mixed salts in a surface soil close to the Dead Sea. Irrigation water is needed to supply the evapotranspiration needs of the crop. To leach salts out of the root zone to maintain acceptable salinity and sodicity levels extra water is needed which, expressed as a fraction of the total water use, is known as the leaching fraction.
