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Soil salinity has caused heavy loss of national wealth in India.
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Out of 329 million hectares of land in the country, about 175 million ha. (53 %) is suffering from degradation in some form or the other.
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There are 7.61 M ha of salt affected soils in India as per the Ministry of Agriculture, GOI.
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The extent of this problem area as given by different sources varys from 8.56 M ha to 10.9 M ha.
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Water logging affects another 8.52 M ha mainly in the irrigation commands, which includes some of the saline-alkali soils also.
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In Haryana, parts of Punjab, Rajasthan, Uttar Pradesh, Gujarat, Maharashtra, Madhya Pradesh, Karnataka, Andhra Pradesh and Tamil Nadu, substantial areas of good irrigated lands are affected by saline-alkali and water-logging problems.
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There are several reasons for development of salinity in the soils, such as,
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Excessive and uncontrolled irrigation.
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Accumulation of salts in the top layer due to evapo-transpiration in arid conditions.
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Water logging conditions in perennial river basins/ irrigation sources due to seepage.
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Excessive use of chemical fertilizers containing chlorides, sulfates etc.
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Poor drainage conditions.
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The problem of salinity, alkalinity and water logging deserve special treatments based on the local conditions and soil texture, structure and topography.
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When water is used for agricultural purposes, in most cases more than 50 percent goes waste.
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It seeps out of unlined channels, pipes, ditches, runoff fields or percolates in to the soil and accumulate in uneven depressions.
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Water dissolves naturally occurring salts in the rocks and soils and carries them to the surface of the soil, where the water molecules evaporate, leaving the salts to accumulate near the surface.
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Excess salts, eventually will lead to alkali problem.
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The growing problem of salinity-alkalinity should be minimised or eliminated as early as possible since it is growing at the rate of 10% every year.
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Soil salinity has become an acute problem rendering crop productivity to decline or making the soil unfit for cultivation. Irrigation has both sides of bane and boon. Unscientific irrigation has endangered many favorable environmental conditions and human health.
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The Government/people have now realised the seriousness of the problem. In the absence of adequate drainage provisions, with the introduction of new irrigation projects and also the faulty water management practices on the farms, additional area will turn salty each year.
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Saline soils contain soluble salts which impair the soil productivity. Such soils can normally be identified by the presence of white crusts of salts on the surface of the land area and poor crop growth. Internal drainage of such soils will not be bad. By opening adequate drains, such soils can be improved.
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Drainage becomes a problem when the soil is water logged. In such soils, the aeration will be a limiting factor and microbial activities will be hindered and hence the removal of excess water from such water logged areas becomes very essential.
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On the other hand, sodic soils containing excess sodium become extremely water-logged as the soil porosity is lost and water do not percolate down easily / quickly. In case of excess Sodium contents of the soil, it has to be treated with soil amendments such as gypsum, sulfur etc., and then the salts have to be drained. In summary, the basic requirement is provision of adequate and appropriate drainage system.
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Black soils are worst affected as they have poor drainage due to high clay content.
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