usar land.pptx

usar land

1. Environment Science Formation And Reclamation Of Usar Land Submitted By- Gaurav Verma

2. Contents Land as a resource Usar land Formation of usar land Reclamation of usar land

3. Land as a resource Land is the basic and most important resource to the mankind. All agricultural, animal and forestry production depend on the productivity of the land. Land is considered as an important resource as it provides habitation to a wide variety of flora and fauna. It is used by human beings for various purposes such as agriculture, forestry, mining, building houses and roads, and setting up industries.

4. The land resource is limited as the total geographical area is fixed. The amount of land and land-based resources is, then finite. Land is therefore, scarce in supply. Under these conditions, every part of the land is important for us and for the nation.

5. Usar Land/Soils Out of the several problems that limit the economic utilization of land resources in India, the problem of usar lands (Sodic and Saline) - the so called salt -affected soils is of great concern. Deforestation, Excessive use of pesticides and chemical fertilizers,water-logging etc are few causes of land degradation.

6. These soils have developed in areas with dry climatic conditions (in areas having a little more rainfall than the areas of desert soils) accompanied by lack of proper drainage. In this situation, salts of sodium, calcium and magnesium are deposited on the upper layer of the soil by capillary action. Usar land is defined as that land where the vaste patches of white efflorescence salt called ‘ Reh ’.

7. In India alone, about 7 million ha of the cultivated land are affected by sodicity and salinity. Nearly 35 per cent (2.5 million ha) of usar lands are sodic , occurring in parts of the Indo- Gangetic plains. In Haryana, it is about 0.50 million ha. Nearly 65 per cent (0.33 million ha) of the usar lands are sodic , occurring in the Indo- Gangetic plains with mean annual rainfall of 550-1000 mm.

8. These soils are also formed when saline water spreads on the land at the time of high tide in coastal areas. Also, seawater intrusions in the deltas promote the occurrence of saline soils. Salinization also occurs because of over-irrigation (canal irrigation/groundwater use) and in areas of high water table (as in the coastal areas of Maharashtra and Tamil Nadu).Salinity from irrigation can occur over time wherever irrigation occurs. This is because almost all water (even natural rainfall) contains some dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually begin to accumulate. Also, excessive irrigation with dry climatic conditions promotes capillary action, which results in the deposition of salt on the top layer of the soil

9. They occur in arid and semi-arid regions, and in waterlogged and swampy areas. These are more widespread in western Gujarat, deltas of the eastern coast and in Sunderban areas of West Bengal.

10. Other characteristic features: Because of capillary action, the salts are sucked up in solution to the surface and form white encrustations on the surface.

11. Source The salt efflorescence of calcium, magnesium and sodium makes these soils infertile. Saline soils contain an excess of neutral soluble salts of chlorides and sulphates whereas sodic or alkali soils contain sodium carbonates/ sodium bicarbonates. They lack in nitrogen and calcium and have low water bearing capacity. These soils can be reclaimed by improving drainage, by applying gypsum and/or lime, and by cultivating salt resistant crops like barseem , dhaincha and other leguminous crops. The saline and alkaline soils may occur in any group of soils.

12. Crops grown: In coastal areas, coconut trees are found in plenty in these soils. As discussed above, cultivating salt resistant crops like barseem , dhaincha and other leguminous crops can help in reclaiming these soils. Note: In the areas of intensive cultivation with excessive use of irrigation, especially in areas of green revolution, the fertile alluvial soils are becoming saline. In such areas, especially in Punjab and Haryana, farmers are advised to add gypsum to solve the problem of salinity in the soil.

13. Reclamation The reclamation of sodic soils basically requires that the excess sodium in the exchange complex should be replaced with calcium and exchanged sodium be leached out of the root zone.

14. Reclamation of Sodic Soil by displacement process Reclamation or improvement of Sodic soils requires the removal of part or most of the exchangeable sodium ion and its replacement by the more favourable calcium ions in the root zone. Soil amendment materials such as gypsum or calcium chloride directly supply soluble calcium for the replacement of exchangeable sodium, or other substances, such as sulphuric acid and sulphur that indirectly through chemical or biological action, make the relatively insoluble calcium carbonate commonly found in sodic soils, available for replacement of sodium.

15. The application of mined-gypsum in soils and addition of sulphuric acid to sodic soil surface reduce soil crusting and improve water infiltration rate. Organic matter (straw, farm and green manures), decomposition and plant root action also help to dissolve the calcium compounds found in most soils, thus promoting reclamation but this is relatively a slow process.

16. Gypsum Application These soils can be brought successfully under cultivation by adoption of reclamation and management technology. The key to success is the availability of good quality water and a cheap source of gypsum. The main features of the technology are:  The leaching of excess salts from the soil surface layers.  The supply of adequate quantities of soluble calcium (like gypsum) to improve the soil chemically and physically.

17. Organic Material The application of organic materials ( pressmud -a by product of sugar industry, FYM, green manures, rice husk, saw dust, charcoal dust, molasses), either alone or in combination with other amendments, has also proved beneficial at several places. Besides being a source of plant nutrients, these materials, when decay, liberate large amounts of carbon dioxide and organic acids which react with the native calcium carbonate to form soluble calcium salts and consequently decrease the soil ESP and pH

18. Use of Saline Water as a Source of Calcium Another development in the reclamation of sodic soils is the high salt dilution method in which the soil is leached with saline water in successive dilutions.

19. Irrigation For crop other than rice, their irrigation presents the major difficulty in obtaining their optimum yields from sodic soils. The low infiltration rates and the low hydraulic conductivity of these soils result in a reduced water storage in the profile. The root penetration in these soils is restricted due to a dense and high ESP sub-soil.

20. Fertilization Fertilization The low organic matter content and the high pH impart poor fertility to the sodic soils. Due to low levels of nitrogenous in these soils, the application of nitrogen in these soils, the application of nitrogenous fertilizers is particularly important. A number of studies have shown that crops grown in sodic soils respond more to the higher levels of applied nitrogen than crops grown in non- sodic soils.