Historical Perspectives and Dynamics of Nature, Extent, Classification and Management of Salt-affected Soils and Waters

Abstract

Soluble salts are a natural feature of the landscape, being present usually in small amounts in all soils, waters and rocks. It is only their accumulation beyond a certain proportion that creates a salt land. Soil salinization is an in situ form of soil degradation that arises due to the buildup of soluble salts to deleterious levels at or near the soil surface. Being one of the oldest environmental problems, salinization has been considered as ‘one of the seven main paths to desertification’ and a major process of land degradation. Salt-affected soils occur in about 100 countries under different environmental conditions and have diverse morphological, physical, chemical, physico-chemical and biological properties, but one common feature, the dominating influence of electrolytes on the soil-forming processes, joins them into one family. There are many classification systems for salt-affected soils, while a large number of systems exist in individual countries, particularly in those where salt-affected soils are common. Saline soils develop mainly under the influence of sodium chloride and sulphate and closely associated with deserts and semiarid regions and seldom occur in subhumid and humid regions. Alkali soils, formed under the influence of sodium ions capable of alkaline hydrolysis, occur mainly in semiarid, subhumid and humid regions, but they can also be found under practically any environmental conditions.