Lecture Notes on Irrigation AGEN 401: 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 which 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 dusts 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 which
concentrate the salts. The main origin of salts in the soil is from the
weathering of parent material of soil or rock which include hydration,
oxidation, carbonation etc. however, hydrological conditions and poor
managements 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 soil surface from high water table
3
Arid
region (high evaporation)
4
Poor
drainage (non leaching)
5
Water
back flow or intrusion of sea water in
coastal areas
All the above factors either singly
or in association with each other are responsible to salt accumulations in
soils
No comments:
Post a Comment