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Ch 6: Soils (Soil Erosion ("destruction of the soil cover", Wind…
Ch 6: Soils
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Factors affecting soil formation: relief, parent material, climate, vegetation and other life-forms and time.
Components of soil: mineral particles, humus, water and air
Classification
Alluvial
Location: Northern plains and river valleys, through a narrow corridor in Rajasthan, extend into plains of Gujarat, deltas of east coast and in the river valleys
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Black
Location: Deccan Plateau (Maharashtra, MP, Gujarat, AP, TN)
In the upper reaches of Godavari and Krishna, NW of Deccan Plateau => very deep
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Swell and become sticky when wet and shrink when dried => during dry season => wide cracks => self ploughing
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Rich in lime, Fe, Mg, Al. also contain K but lack P, N and organic matter
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Red and Yellow
Location: develops on crystalline igneous rocks in areas of low rainfall in the E and S part of Deccan Plateau, piedmont zone of the Western Ghat, Odisha, Chhatisgarh, southern part of middle Ganga plain.
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Laterite
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Poor in organic matter, N, P and Ca, but rich in Fe-oxide and K. => not suitable for cultivation
Red laterite in TN, AP, Kerala => tree crops like cashewnut.
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Location: Karnataka, Kerala, TN, MP and the hilly areas of Odisha and Assam.
Arid
Red to brown in colour, sandy in structure and saline in nature
Lack moisture, humus and organic content
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Saline
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Larger proportion of Na, K and Mg => infertile, No vegetative growth.
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Location: western Gujarat, deltas of the eastern coast and in Sunderban areas
Rann of Kuchchh => SW monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils. Intensive cultivation with excessive use of irrigation => fertile alluvial soils are becoming saline. Excessive irrigation with dry climatic conditions promotes capillary action, which results in the deposition of salt on the top layer of the soil.
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Peaty
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Location: northern part of Bihar, southern part of UK and the coastal areas of WB, Odisha and TN.
Forest
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In the snow-bound areas of the Himalayas => denudation, and are acidic with low humus content.
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Soil Survey of India 1956, National Bureau of Soil Survey and the Land Use Planning under Indian Council of Agricultural Research (ICAR)
Soil Degradation
decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse
Soil Erosion
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Sheet erosion takes place on level lands after a heavy shower and the soil removal is not easily noticeable
Gully erosion on steep slopes deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation
A region with a large number of deep gullies or
ravines is called a badland topography e.g. Chambal Basin, TN and WB
Eroded materials are carried down to rivers => lower down their carrying capacity => frequent floods and damage to agricultural lands.
Plants keep soils bound in locks of roots => prevent erosion. Add humus to the soil by shedding leaves and twigs.
Irrigation => salt lodged in the lower profiles of soil comes up to the surface and destroys its fertility.
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Soil Conservation
Check open cultivable lands on slopes from farming. A slope gradient of 15-25% shouldn't be used for cultivation
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Over-grazing and shifting cultivation => extensive erosion => should be regulated and controlled by educating villagers about the consequences
Contour bunding, Contour terracing, regulated forestry, controlled grazing, cover cropping, mixed farming and crop rotation
Finger gullies can be eliminated by terracing. In bigger gullies => by constructing a series of check dams. Headward extension of gullies => by gully plugging, terracing or by planting cover vegetation
Experiments have been made to stabilise sand dunes in western Rajasthan by the Central Arid Zone Research Institute (CAZRI)
Lands should be classified according to their capability; land use maps should be prepared and lands should be put to right uses.