NCERT Solutions for Class 11 Geography Chapter 23 - Natural Soils

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(a). Alluvial Soil

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(c). Black Soil

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(a). Wind Erosion

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(c). Over Irrigation

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The topmost layer of the crust is called the crust. It is the most important layer of the earth’s crust and is a valuable resource. Soil is the mixture of rock debris and organic materials which develop on the earth’s surface.

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The major factors affecting the formation of soil are
(a) relief
(b) parent material
(c) climate
(d) vegetation and other life-forms
(e) time.
Besides these, human activities also influence it to a large extent.

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Soil consists of three layers which are called horizons.
(a) ‘Horizon A’ is the topmost zone,
(b) ‘Horizon B ’ is a transition zone between the ‘horizon A’ and ‘horizon C’,
(c) ‘Horizon C ’ is composed of the loose parent material.

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Soil degradation can be defined as the decline in soil fertility, when the nutritional status declines and depth of the soil goes down due to erosion and misuse. Soil degradation is the main factor leading to the depleting soil resource base in India. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of the rainfall.

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Soil. Soil is the loose material which forms the layer of mantle rock. India is primarily an agricultural country. The success of agriculture depends upon the fertility of soils. The soils of India are classified into three main groups depending upon the rock cover and climatic conditions :
(A) Soils of the Peninsular India.
(B) Soils of the Northern Plains.
(C) Soils of the Himalayas.
(A) Soils of the Peninsular India.
(1) Black soils. Black soils are mainly found over the Deccan Lava tract including Maharashtra, Madhya Pradesh, Gujarat and Andhra Pradesh. These soils are found in river valleys of Narmada, Tapti, Godavari and Krishna. These soils have been formed due to weathering of Lava rocks. These soils cover an area of about 5 lakh sq. km. These soils are rich in lime, iron, magnesia and alumina. But these lack in phosphorus, nitrogen and organic matter. These are also called ‘Regur’ Soils. These soils are most suitable for cotton cultivation and are known as ‘Black Cotton Soils’. These soils are compared with Chernozem soils of

Russia and Praries soils of U.S.A. These soils can hold water. These soils are suitable for rice, wheat, jowar, sugarcane, tobacco and oil seeds.
(2) Red Soils. These soils are found in Tamil Nadu, Karnataka, Andhra Pradesh and areas on periphery of Deccan Plateau. These soils have been formed due to decomposition underlying Igneous rocks. The red colour of these soils is due to oxidation and diffusion of iron in hard crystalline rocks. These are given to the cultivation of millets, pulses, linseed, tobacco etc. These soils cover the largest area in Peninsular India. These soils are poor in lime, nitrogen and humus. Fertilizers are added to make these fertile.
(3) Laterite Soils. Laterite soils are found on the highland areas of the plateau. These are found in Karnataka, Kerala, Tamil Nadu and hilly regions of Assam, Rajmahal hills and Chhotanagpur plateau. Due to monsoonal climate (wet and dry seasons alternately occurring), there is the leaching of soils. It washes away the silica current in soils. These are shallow, acidic and less fertile soils. The lowland laterite soils are useful for cultivation of foodgrains and other crops. The upland laterites are thin, coarse and infertile. These soils are poor in nitrogen and lime, but rich in iron. So these are suitable for plantation crops like tea, rubber, coffee, etc.
(4) Alluvial Soils. These soils have been deposited by the rivers in river valleys of Mahanadi, Godavari, Krishna and their deltas. These are deep and fertile soils. These are dark soils. These soils are suitable for cultivation of Jute, Rice, Sugarcane etc.
(B) Soils of the Northern Plains
(1) Alluvial Soils. These soils are the most wide spread soils covering an area of 8 lakh sq. km. from Punjab to Assam. These cover about 43.7% area of India. These soils have been deposited by sediments brought by rivers. These are found in river basins, flood plains and coastal areas. These are deep soils rich in potash, but poor in nitrogen. These are of three types :
(i) Khadar Soils. The finer and new alluvium deposited in flood plains is called Khadar Soils.
(ii) Bangar Soils. The older alluvium is known as Bangar soils.
(iii) Newest Alluvial Soils. The fine alluvium in deltas is known as newest alluvial soils.
(2) Desert Soils. These soils cover 2 lakh southern area in dry area of Rajasthan, Gujarat, Punjab, Haryana. These coarse soils are suitable for cultivation of Jowar, Bajra, Cotton etc.
(3) Saline and Alkaline Soils. These soils are found in dry and marshy areas. These are locally known as Thur, Reh, Kallar. The accumulation of salts makes these infertile.
(C) Soils of the Himalayas
These mountain soils are mostly thin and infertile. These include :
(i) Stony soils which are coarse and infertile.
(ii) Tea soils found in Dun valleys are suitable for Tea cultivation.
(iii) Volcanic soils are found on mountain slopes.
(D) Peaty and Organic Soils They are found in the areas of heavy rainfall and high humidity, where there is a good growth of vegetation. So large amount of dead organic matter accumulates in these areas, and this gives a rich humus and organic content to the soil. Hence, they are peaty and organic soils. Organic matter in these soils may go even up to 40 to 50 per cent. These soils are normally heavy and black in colour. At many places, they are alkaline also. It occurs widely in the northern part of Bihar, southern part of Uttrakhand and coastal areas of West Bengal, Odisha and Tamil Nadu. Such soils are used for cultivation of light and less soil exhaustive crops.
(E) Forest Soils As the name goes, forest soils are formed in the forest areas where sufficient rainfall is available. The soils vary in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained in the up slopes. In the snow-bound areas of the Himalayas, they experience denudation, and are acidic with low humus content. The soils found in the lower valleys are fertile and are used for cultivation of rice and wheat.

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We can known a particular soil is fertile or not on basis of its colour, texture, humus, mineral content, etc.
Natural fertility of the soil is determined on the basis of fertility grained by fallow soil, which is used for crop production rotation wise, while culturally included fertility by adding external inputs like organic manure to the soil.

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SOIL CONSERVATION : If soil erosion and exhaustion are caused by humans, they can also be prevented by humans. Soil conservation is a methodology to maintain soil fertility, prevent soil erosion and exhaustion, and improve the degraded condition of the soil.
Soil erosion is essentially a man-made problem.
(1) The first step in any rational solution is to check open cultivable lands on slopes from farming. Lands with a slope of 15 to 25 per cent should not be used for cultivation. If at all the land is to be used for agriculture, terraces should carefully be made.
(2) Over-grazing and shifting cultivation in many parts of India have seriously affected the natural cover of land and given rise to extensive erosion. They should be regulated and controlled by educating villagers about the consequences.
(3) Contour bunding, contour terracing, regulated forestry, controlled grazing, selective weeding, cover cropping, mixed farming and crop rotation are some of the remedial measures which are often adopted to reduce soil erosion.
(4) Efforts should be made to prevent gully erosion and control their formation. Finger gullies can be eliminated by terracing. In bigger gullies, the erosive velocity of water may be reduced by constructing a series of check dams. Special attention should be made to control headward development of gullies. This can be done by gully plugging, terracing or by planting cover vegetation.
(5) In arid and semi-arid areas, efforts should be made to protect cultivable lands from encroachment by sand dunes through developing shelter belts of forests. Lands not suitable for cultivation should be converted into pastures for grazing. Efforts should be made to stabilise sand dunes.
Some important and well known measures to conserve soils are as follows :
(1) Scientific land use, i.e., using land for the purpose it is most suited.
(2) Scientific crop rotation.
(3) Contour ploughing and bunding
(4) Afforestation specially in the upper reaches of river basins.
(5) Construction of barriers against water gullies in wet regions and against winds in desert and semi-desert regions.
(6) Increased use of organic manures, and
(7) Replacing flood irrigation by sprinkler and drip irrigation.