Soil is defined as the upper most part of the earth's crust on which vegetation grows. The scientific study of soils is termed as Pedology. The soil is an important resource as it provides a medium for plant growth. At a very general level, soils can be classified as (i) in-situ soils or sedentary soils (ii) Drift soils. In situ soils are those which are formed directly from the underlying rocks. Examples of in-situ soil type are black soils, red soils, laterite soils, saline and alkaline soils, peaty & organic soils and forest soils. The drift soils are those soils which are formed elsewhere but carried from their place of formation by agencies such as water & wind and deposited in new places such as deltas, valleys and deserts. These soils are deep and very fertile compared to in-situ soils.
Of the several types of soil classifications the classification adopted by the Indian Council of Agricultural Research (I.C.A.R.) is the most popular. ICAR has classified soils in India into 8 major types. They are (1) Alluvial soils (ii) Black soils (iii) Red soils (iv) Laterite soils (v) Forest soils (vi) Arid and Desert soils (vii) Saline & alkaline soils (viii) peaty & Marshy soils. Of these eight groups almost 80% of the total land surface and almost the entire cultivated area is located in regions of alluvial, black, red and laterite soils.
The various characteristics and the distribution of the 8 soil groups is given below:
(I) ALLUVIAL SOILS:The alluvial soils cover nearly one-fourth of the total land surface of India and are the most intensively cultivated areas. Their areal extent is 7.71 lakh sq.kms. Those soils are derived mainly from the debris brought down from the mountain ranges. These soils are very fine grained, highly porous and light and so are easily tilled. Further, these soils arecomposed of material drawn from different rocks and therefore contain a variety of salts which contribute to their fertility. These soils are rich in Potash, Phosphoric acid, lime and organic matter but are deficient in nitrogen and humus contents.
These soils are suitable for rice, sugarcane, tobacco, banana, cotton, wheat, jute etc.
The soils are distributed in parts of Eastern Rajasthan, Punjab, Haryana, U.P., Bihar, parts of Assam, West Bengal, East and West Coastal plains in Southern India.
The major problem with these soils is that they allow water to sink into lower strata and so are unsuitable for the growth of those crops which require retention of moisture at their roots. Further, the soils are deficient in nitrogen and humus contents. These defects can be offset by providing irrigation and adding nitrogenous fertiliser to the soils.
(II) BLACK SOILS OR REGUR SOILS:These soils cover an areal extent of about 5.5 lakh km2. These soils are derived from Deccan lavas. The soil is clayer and fine textured with dark colour. These soils are highly retentive of moisture and extremely compact when wet. They are generally rich in Iron, Lime, Calcium, Magnesium carbonates and alumina & are best suitable for cotton, Tobacco. Cultivation of certain dry crops like wheat, chillies, linseed, Jowar, etc.
The black soils are found in the states of Maharashtra, Gujarat, Karnataka, A.P., M.P., Some parts of Tamilnadu, Rajasthan & U.P.
The main problems with these soils is that they are clayey and expand durring the rainy season and contract during the dry season exhibiting broad & deep cracks. This causes foundation problems to the buildings constructed on these soils. Further, when the black soils are wet they become extremely compact and especially in the rainy season they became unworkable as the ploughs get stuck. The soils are also deficient in phosphorous, nitrogen & organic matter which have to be supplied to increase the fertility.
(III) RED SOILS:These soils cover an areal extent of about 5.18 lakhs km2 of area. These soils are developed from the granite and gneissic rocks of the peninsula. The high content of iron compounds give them the red colour. The soil is sandy & loamy in texture. These soils are rich in Potash.
Red soils are suitable for crops like cotton, wheat, pulses, tobacco, Jowar, linseed, potatoes and fruits.
The soil is distributed practically in the whole of Tamilnadu, parts of Karnataka, South Eastern Maharashtra, North-Eastern A.P., Eastern part of M.P. to Chota Nagpur and parts of Orissa & Bihar, parts of MP & West Bengal, Eastern half of Rajasthan, Southern Part of Assam and other north Eastern States. This is the most extensive of all the soil groups.
The problem in Red soils is that they are poor in lime, humus, iron oxide, phosphoric contents and also nitrogen. They can be set right by the addition of deficient minerals in required quantities. Irrigation is necessary since they cannot hold moisture for a longer time.
(IV) LATERITE SOILS:These soils have an areal extent of 5.18 lakh km2. It is an end product of decomposition found in regions of heavy rainfall (greater than 200 cm). which promotes leaching of lime & silica from soil leaving behind rich oxides of iron and aluminium. It is due to the presence of iron oxides that the soil appears red in colour.
These soils are well developed on the summits of hills & plateaus and are generally infertile. Yet crops like Cashew, Eucalyptus, Casuarina are grown. Rice, ragi, sugarcane, Tapioca are grown.
The soils are found on the hills and plateaus of Vindhyas & Satpuras and associated ranges in M.P., West Bengal, Eastern Ghat region of Orissa, parts of Assam, South Maharashtra, Karnataka, Kerala. In A.P. they are seen in Tada, Kavali & Ongole area.
The problem with these soils is that lime and silica are leached away. The soils are generally poor in nitrogen, potash and organic matter. The deficient constituents are to be supplied to the soil to remedy the deficiencies.
(V) FOREST SOILS: These soils cover an areal extent of 2.9 lakh km2. These soils occur on the slope of mountains & hills and contain large quantities of decomposed leaves, flower and humans. These soils are rich in Nitrogen and organic matter. The soils are suitable for plantations of tea, coffee, spicies & fruits.
These soils are found on the slopes of Himalayas, Sahyadris (Western Ghats) and Eastern Ghats.
The main problem with these soils is that they are deficient in potash, phosphorous & lime and they can give high yeilds only if fertilisers are applied.
(VI) ARID AND DESERT SOILS:These soils occupy an areal extent of 1.4 lakh sq.km. These soils are predominantly sandy in texture. They are formed from the disintegration of adjacent rocks and also from the accumulation of sand from the winds browing fom coastal regions. These soils contain high percentage of soluble salts and varying percentage of calcium carbonate.
These soils are rarely used for cultivation. Very few crops especially coarse millets, jowar and bajra are grown.
This soil is found in the Western Rajasthan, Haryana, South Punjab to the West of Aravalli mountain ranges.
The main problem with the desert soils is that they are poor in organic matter and deficient in sub-soil moisture. These soils can be reclaimed if proper facilities of irrigation are available and other soil nutrients are supplied.
(VII) SALINE AND ALKALINE SOILS: They are temporary ones. These soils are very infertile and are also called 'reh', 'kallar' or 'Usar'. This kind of soils are formed in places where there is excessive irrigation coupled by poor drainage as a result of which sub-soil water table is high leading to salt formation on the soil surface. They are also formed during dry season when salts are sucked up by capillary action on to the surface and deposited.
These soils are suitable only for salt resistant crops like berseem, rice & sugarcane.
The soils are distributed in the drier tracts of north India specially in parts of Rajasthan, Haryana, punjab, U.P. & Bihar.
The main problem with these soils is that of salt accumulation due to evaporation of moisture in dry season. Excessive canal irrigation in the absence of proper drainage is deterimental to plant growth. These soils can be corrected by the application of calcium, nitrogen & Gypsum wherever necessary and providing proper sub-soil drainage.
SCHEME OF RECLAMATION OF ALKALINE SOILS:A centrally sponsored scheme of reclamation of alkali soils was taken up in Punjab, Haryana and Uttar Pradesh during the 7th Plan.
The Scheme was further extended to Gujarat, Madhya Pradesh and Rajasthan during the 8th Plan.
This scheme aims at improving the physical conditions and productivity status of alkaline soils for restoring optimum crop production.
The major components of the scheme include assured irrigation water on farm development works like - land levelling,
- Bunding and ploughing
- Community drainage system
- Application of soil amendments
- Organic measures, etc.
An area of 0.65 million hectares out of 3.58 mhs of alkali lands has been reclaimed till the end of 1999-2000.
(VIII) PEATY AND MARSHY SOILS: The areal extent of the soils is very less i.e. about 150 sq.km. Peaty soils originate in humid regions as a result of an accumulation of large amount of organic matter in soil. The soils are black, heavy & acidic.
The crop which is grown on these soils is paddy.
These soils are found in parts of Kerala.
Marshy soils are formed as a result of water-logging.
They have iron and organic matter.
They are not suitable for cultivation. They are found in coastal tracts of Orissa, West Bengal (Suderbans), Central Portion of north Bihar & Parts of U.P.
The main problem in these soils is excessive water logging which prevents crop growth. |
RIVER SYSTEM IN INDIA
The rivers of India can be divided into two main groups i.e. the Himalayan rivers (Prerennial) and the rivers of the Peninsula (Non-perennial)
The important Himalayan rivers systems are the Ganga, the Indus and the Brahmaputra.
1) THE GANGA SYSTEM:The Ganga system covers about 1/4th of the total area of the country and is 2525 Kms long in India. The Ganga is formed by joining of two head streams, the Bhagirathi, which rises in Gangotri and the Alaknanda which rises near the Garhwal Himalayas. Tibet border, both in the himalayas. Its main tributaries from the north are the Yamuna, the Ramganga, the Gomati & the Ghagra, the Kosi.
The tributaries like Chambal Son Damodar drain from the South. The greater part of the Ganga basin is in the states of U.P., Rajasthan, M.P., Bihar & West Bengal. Since it is flowing through Bangladesh it is called 'international river'. In Bangladesh it is called as 'Padma'.
2) THE INDUS SYSTEM:The Indus system covers only 1/3rd of the area of the Ganga basin in India and is 709 Kms long in India. Its tributaries are - Jhelum
- Chenab
- Ravi
- Beas
- Sutlej
The river system helps in irrigation, in the states of Punjab, Haryana & Rajasthan. The Indus river rises in Manas Sarovar in Tibet (to the north of Himadri ranges).
3) THE BRAHMAPUTRA BASIN:The river Brahmaputra also has its origin in lake Manas sarovar, Tibet. Its length in India is 885 Km. But the volume of water in the Brahmaputra basin is nearly four times than that of Indus system as the region receives heavy rainfall. The main tributaries of the river are Raka, Tsangpo, Dihing, Dibang, Lohit, Subansiri, Dhansiri, Manas, Tista. The river covers the states of Assam, West Bengal & Arunachal Pradesh in India. The river is called as Dihang in Arunachal Pradesh and Tsanpgo in Tibet. The river is subjected to frequent floods and carries large quantities of silt. Its upper course is in Tibet middle course is in India & the lower course is in Bangladesh. It is an International river too. The delta of Ganga and Brahmaputra is called as 'Sundarbans'.
RIVERS OF THE PENINSULAR INDIA: The important rivers of the peninsular India are the Godavari, the Krishna, the Mahanadi, the Cauvery, the Narmada and the Tapti. Only the rivers Narmada & Tapti along with two other minor rivers i.e. the Luni and the Sabarmati drain into the Arabian sea. All other rivers drain into the Bay of Bengal. A brief note on each of these rivers is given below.
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The Narmada: The river rises in the Amarkantak plateau in M.P. It flows in a rift valley between the Vindhya and the Satpura ranges. It is the longest and largest among the west flowing rivers. It passes through M.P., Maharashtra & Gujarat.
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The Tapti: Rises near Multai in Betvl district of M.P. It is the second longest west flowing river. this river flows along a fault line and has a narrow basin. It passes through Maharashtra, M.P., Gujarat.
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The Godavari: The river raises near Nasik in Maharashtra. This is the largest, next only to the Ganga basin in the area drained. The Godavari basin includes about 10% of the total area of India. The river passes through Maharashtra, M.P., & A.P. Its important tributaries are Manjira, Penganga, Weinganga, Indravati. The lower portion of the river is liable to floods.
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The Krishna: The source of the river is near Mahabaleshwar in Maharashtra. This is the second largest east flowing river after the Godavari. The river flows through the states of Maharashtra, Karnataka and M.P. Its main tributaries include Koyna, Panchanganga, Ghataprabha, Malaprabha, bhima and Tungabadra.
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The Mahanadi: The Mahanadi river has its origin near Raipur in M.P. The river flows through M.P. & Orissa. Its main tributaries are Hasdeo, Seonath, Jonk etc. The river causes floods in the Monsoon season.
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The Cauvery: It rises in the Coorg district of Karnataka. The river descends the plateau through a waterfall at Sivasamudram. The waters of the river are utilised by the States of Karnataka, Tamil Nadu & Kerala. The main tributaries of the river are Hemavati, Lokpavani, Amaravati etc.
DIFFERENCES BETWEEN THE HIMALAYAN & PENINSULAR RIVERS
The Himalayan rivers are both rainfed and snowfed and hence perennial. They do not show large seasonal variations. The Peninsular rivers derive their supply only from the rainfall. Hence they are characterised by heavy discharges during the monsoons followed by low discharges during the rainless months.
The Himalayan rivers flowing in the great northern plains are free to develop their courses in alluvial sediments and follow a general dendritic pattern (free like when viewed from above). the Peninsular rivers however follow the trend lines and joints in the crystalline rocks.
The Himalayan rivers drain high mountainous region and descend steep slopes. As a result these rivers erode their valleys into deep gorges. The Peninsular rivers encounter a senile topography and so they flow in broad valleys with gentle slopes.
The Himalayan rivers are called antecedent rivers as their courses are older than the mountain ranges. As the mountain ranges got uplifted slowly, the rivers have maintained their course by cutting deep gorges. It is the reverse in case of Peninsular rivers that is mountains formed first in Peninsular India and later rivers.
The Himalayan rivers are best suited for irrigation as they are perennial and canals can be easily dug in the alluvial lowlands of the Northern plains. The rivers of the Peninsula are well suited for hydro-electric power development.
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