Saline and Alkaline Soils

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Lecture Notes on Irrigation AGEN 501: Salinity And Water Quality

Prepared by Engr M. K. Othman (PhD)

Sources / Causes of soluble salts in Soils

Salinization is a major problem associated mostly with arid lands. It is estimated that 10 to 50 per cent of all irrigated land in the world is adversely affected by salinity.

Many processes, both natural and man-induced, result in salinization. Salinization requires a source of salt, a process that concentrates the salt and impaired drainage. Sources of salts include the natural weathering of minerals and redeposition of the salts at another location, the importation of salts in water used for irrigation, the deposition of rainfall with low concentrations of marine salts, and the transportation of salts in airborne dust from dry salt beds. Natural weathering of geological salt deposits is a major source of salts in arid regions. The weathering of non-saline minerals can also be important when combined with processes that concentrate the salts. The main origin of salts in the soil is from the weathering of the parent material of soil or rock which include hydration, oxidation, carbonation etc. however, hydrological conditions and poor management of irrigation schemes contribute substantially to the development of soil salinity and alkalinity. (Excess exchangeable salt and excess exchangeable sodium)

These are 

1 Use of saline water in irrigation

2 Deposition of salts on the soil surface from the high water table

3 Arid region (high evaporation)

4 Poor drainage (non-leaching)

5 Water backflow or intrusion of seawater  in coastal areas

All the above factors either singly or in association with each other are responsible to salt accumulations in soils