Alkaline soil , Origin, Properties and Distribution in India

Alkaline soil , Origin, Properties and Distribution in India

1. ALKALINE SOIL:- ORIGIN, PROPERTIES AND DISTRIBUTION

2. INRODUCTION :- Alkaline soils are clay soils with a high pH (>9) and a poor soil structure and a low infiltration capacity. The causes of soil alkalinity are natural or they can be man made. The natural development is due to the presence of soil minerals producing sodium carbonate & sodium bicarbonate upon weathering. The man made development is due to the application of irrigation water (surface or ground water) containg a relatively high proportion of sodium bicarbonates. Alkaline soils are difficult to take into agricultural production.

3. UNIT OF EXPRESSION OF ALKALINITY :- Sodium is involved in alkalinity. It is expressed in terms of exchangeable sodium percentage (ESP) which is degree of saturation of exchangeable complex with sodium absorption ratio (SAR) which is a comparative ratio of Ca, Mg and Na. In the case of alkaline soils, the exchange complex contains appreciable quantities of exchangeable sodium . such soil may or may not contain excess salts.

4. Alkaline soils may be divided into following groups:- Saline- alkali soil :- when they contain soluble salts in excess they are known saline- alkali soils . Non- saline -alkali soil :- when they do not contain soluble salt, they are called non saline alkali soil. Degraded alkali soil :- under certain circumstances the clay complex is broken down to give rise to degradable alkali soil.

5. ORIGIN AND FORMATION OF ALKALINE SOIL Hydrolysis of sodium saturated exchange complex in the formation of an alkali soil :- sodium carbonate undergoes hydrolysis to form sodium hydroxide .which dissociated to increase concentration of hydroxyl ions in soil solution. Formation of OH ions is an increase in pH . Arid and semi arid climate:- salt affected soils are mostly formed in arid region where low rainfall and high evaporation prevails. The low rainfall or precipitation in these regions is not sufficient to leach out the soluble weathered products and hence the salts accumulate in soil. In dry weather, the salts move up with the water and are brought up to surface where they are diposite as the water evaporates. Salty underground water :- if the ground water is salty, the salts move upward with water and get deposited when water evaporate.

6. CONTINUE.... Overflow of sea water over lands:- low-lying areas near the sea which get sea water during tides. salt water accumulates and enrich the soils with salts. Quality of irrigation water:- if water contains excessive amount of calcium, Magnesium, sodium, chloride, carbonate their continuous application develops salt affected soils. Excessive use of basic fertilizer:- use of alkaline fertilizer like sodium nitrate basic slag etc., may develop alkalinity in soil. Humid and semi-humid regions:- alkaline soils develop in other areas also, Eg . In semi-humid and temperate region, especially in depression where drainage is defective and where the under ground water table is high and enrich the soils with salts.

7. NATURE AND PROPERTIES Physical properties: alkali soils are deflocculated thats why soil is impermeable to water and air . High amount of exchangeable sodium leads to dispersion of the clay, which together with humus may form dark coloured soil. In alkaline soil organic matter content is very low.

8. CONTINUE .... Chemical properties:- The pH value of alkaline soils ranges from 8.5 to 10.5 The SAR value of alkaline soil is >13. The ESP value of alkaline soil is > 15. In alkaline soil total soluble salt content is < 0.1% In alkaline soil dominant salts are sodium carbonate and bicarbonate. EC value is <4 ds /m.

9. CONTINUE.... Availability of nutrients:- the high pH in alkali soil cause a reduction in the availability of plant nutrients such as phosphorus, calcium, nitrogen, iron, copper, manganese and zinc. Microbiological activity:- In alkaline soil microbiological activity are reduced.

10. DISTRIBUTION Alkali soil are widespread in many countries of the world, especially in Australia Argentina and Canada. Alkali soil occur most frequently steppe ,dry steppe and semi desert zone. In India alkali soil occur in indo gangatic plains.

11. Area :- parts of Gujarat ,Rajsthan, Panjab, Haryana, uttarPradesh and Maharastra.

12. By - Vaishnavi Raju