Wednesday, 18 May 2016

MAJOR SOIL TYPES IN INDIA


SOIL :


·  Soil is the uppermost layer of Earth’s crust.
·  Soil is the medium in which plants grow and thus it supports the lives on earth.
The soils of India on the basis of their formation are divided in the following two broad catagories :

1.Residual Soil- which form at the place of their origin. Like – black soils
2.Transported Soil- which are transported from place of their formation. Like alluvial soils.

Factors that control the formation of soil :

A number of factors contribute to the soil formation and fertility.
1.Parent rocks: -
·  the rock on which the soil is formed decomposes and disintegrates under the processes of weathering.
·  The characteristics of rocks influence the characteristics of soils. For example on lava rocks black soils and iron oxide rich rocks red soils are formed.
2.Climate: -  climate influence the rate of weathering of rocks and type of vegetation, thus these influence the characteristics of soils.
3.Slope: -the nature of relief and slope influence the accumulation of soils. Mountains have thin soil cover but the plains have thick soil cover.
4.Time: -  time provides maturity to the soil.
5.Various forces of nature such as change in temperature, actions of running water, wind and glaciers, activities of decomposers etc. contribute to the formation of soil.
6.Chemical and organic changes which take place in the soil are equally important.


1. Alluvial Soils :



·  Alluvial soil is the most important soil type of India.
·  It covers the vast valley areas of the Sutlej, Ganga and Brahmaputra and the fringes of the southern peninsula. It is thin near the fringe of the plateau.
·  It covers about 40 percent of land area of the country.
·  They are depositional soils, transported and deposited by rivers and streams.
·  These soils are formed by the deposition of fine sediments and silt by the rivers along their banks.
·  The soils vary from sandy loam to clay in texture and are rich in potash but deficient in nitrogen and organic matter.
·  Generally, the colour varies from grey to reddish brown.
·  These soil are formed of deposits of silt and sand brought down by the rivers flowing from the Himalayas and the Great Indian plateau.
·   Being young, the soils lack profile development.
·  Being extremely productive, these soils are most important from the point of view of Indian agriculture.
·  In delta region, they are ideal for jute cultivation.
·  Almost all crops are grown on these soils.
·  The higher proportion of clay makes the soil sticky and drainage is often poor.

They can be divided into two types:

1. Young Khadar soils:
·  these are newer alluvium of sandy, pale brown composition, found in lower areas of valley bottom which are flooded almost every year.
·  The newer alluvium is a light friable loam with a mixture of sand and silt. It is found in river valley, the floodplains and deltas.
·  It is non phorous, clayey and loamy.


2. Old Bhangar soils:
·  these consist of older alluvium of clayey composition and are dark in colour.
·  On the other hand, the older alluvium lies on the inter fluves.
·  They are coarse in nature, contain kankar (lime nodules), pebbles, gravels. They are found 30 m above flood level of the rivers.
·  Both are different in texture, chemical composition, drainage capacity and fertility.



 2. Black Soils (Regur) :


·  The black soils are found mainly on the Deccan lava region covering large parts of Maharashtra, some parts of Gujarat and Madhya Pradesh and small parts of Karnataka, Andhra Pradesh and Tamil Nadu.
·  16.6 % of the total land area of the country.
·  The soils are formed by disintegration of volcanic basaltic lava.
·  The colour of the soil is generally black due to presence of compounds of aluminium and iron.
·  Rich in lime and iron, magnesia and alumina . Also contain potash .
Lack phosporus, nitrogen and organic matter .
·  The soil is locally known as regur which extends roughly to 64 million hectares.
·  It is generally clayey deep and has low permeability and impregnable.
·  But it’s depth varies from place to place. It is very thick in lowlands but very thin on highlands.
·  The most important characteristics of this soil are its ability to retain moisture even during the dry season.
·   The soils form wide cracks during summer due to moisture loss and swell and become sticky when saturated.
·  Thus, the soil is aerated and oxidised to deep levels which contribute to maintain its fertility.
·  This continued fertility is favourable in the area of low rainfall for cotton cultivation even without irrigation.
·  Other than cotton, this soil is favourable for the cultivation of crops like sugarcane, wheat, onion and fruits.



3. Red Soils  :
·  Red soils cover large part of the Peninsular upland in Tamil Nadu, Karnataka, Goa, South east Maharashtra, Andhra Pradesh, Orissa, Chotanagpur Plateau and Meghalaya Plateau.
·  They encircle the black cotton soil zone.
·  They have developed on the crystalline rocks like granite, gneisses and cover roughly   10.6% of the total land area of the country .
·  Iron compounds are abundant making the soil reddish in colour but they are deficient in organic matter.
·  The red soils are generally less fertile and are not as important agriculturally as the black and alluvial soils.
·  Rich in potash  & Deficient in nitrogen,lime, magnesia, humus and phosphate.
·  But the productive capacity can be raised through irrigation and use of fertilizers.
·  This soil is suitable for rice, millet, maize, groundnut, tobacco and fruits.
·  Red due to its very high iron content .



4. Laterite Soils :


·  laterite = brick (Latin word) These soils are formed under conditions of high temperature and heavy rainfall with alternate wet and dry periods.
·  Thus its formation takes place strictly under monsoon conditions.
·  Residual soils formed by leaching in areas of heavy rain.
·  Leaching is a process in which the nutrients get percolated down below the soil due to heavy rainfall; thus leaving the top soil infertile. Also called DESILICATION.
·  The laterite soils are commonly found in area of high altitude and heavy rainfall in Karnataka, Tamil Nadu, Madhya Pradesh, Jharkhand, Orissa, Assam and Meghalaya extending over 13 million hectares.
·  They generally form under hot and humid climatic conditions.
·  The lateritic soils are particularly found on high flat erosion surfaces in areas of high and seasonal rainfall.
·  Loss of nutrients by accelerated leaching is the most common feature which renders the soil infertile.
·  The lateritic soils Is of coarse texture, soft and friable.
·  It is red due to the presence of iron oxide which is formed by leaching. The soluble plant foods like potash are removed from the top soil leaving alumina and iron oxide.
·  it Is a porus soil, silica is removed from it by chemical action.
·  It Is poor in lime and magnesium, and deficient in
nitrogen.
·  The pebbly crust is the important feature of laterites which is formed due to alteration of wet and dry periods.
·  As a result of weathering, laterite becomes extremely hard.
·  Thus, their characteristics include complete chemical decomposition of the parent rock, complete leaching of silica, a reddish brown colour given by the oxides of aluminium and iron and lack of humus.
·  The crops which are generally grown are rice, millets, sugarcane on lowland and tropical plantation such as rubber, coffee and tea on uplands.



5. Desert Soils :

·  The desert soils occur in western Rajasthan, Saurashtra, Kutchchh, western Haryana and southern Punjab.
·  The occurance of these soils is related to desert and semi-desertic conditions and is defined by the absence of water availability for six months.
·  The soil is sandy to gravelly with poor organic matter, low humus contents, infrequent rainfall, low moisture and long drought season.
·  The soils exhibit poorly developed horizons. Plants are widely spaced. Chemical weathering is limited.
·  The colour of the soil is either red or light brown. Generally, these soils lack the basic requirements for agriculture, but when water is available, variety of crops like cotton, rice, wheat etc. can be grown with proper dose of fertilizers.
·  suitable for drought resistance crops like millets, barley, cotton, maize and pulses.



6. Mountain Soils :
·  The mountain soils are complex and extremely varied.
·  The soils vary from deep alluvium in the river basins and lower slopes to highly immature residual gravelly on higher altitudes.
·  Because of complex topographic, geologic, vegetation and climatic conditions, no large areas of homogenous soil groups are found.
·  Areas of steep relief are mostly devoid of soil.
·  Various types of crops are grown in different regions like rice in valley, orchards on slopes and potato in almost all areas.


7. SALINE AND ALKALINE SOILS :
·  Soils with high proportion of salts and alkalis are called saline and alkaline soils . They are formed due to accumulation of tidal water in adjoining coasts where drainage is poor.
·  They are found in drier parts of Bihar, Rajasthan, U.P., Punjab, Haryana, Maharashtra. These soils contain many salts like sodium,
magnesium and calcium which make them infertile and render unfit for agriculture.

8. MARSHY SOIL :
·  Found in continuously water-logged areas, or marshy areas especially in the coastal regions near the sea or near the deltas.
·  It covers about 56,000 sq km.
·  They are formed as a result of water-logging.
·  It contain iron and varying amount of decayed organic matter.
·  Found in southern parts of Siwaliks, Jammu and Kashmir, U.P.



SOIL EROSION :
·  Soil erosion is described as the carrying away of soil. It is the theft of the soil .
Common Causes :
·  Deforestation
·  Over-grazing
·  Action of wind, water, glacier, etc.
·   Faulty methods of agriculture, over-irrigation, shifting agriculture, wrong ploughing, etc.
·  Other anthropogenic factors(mining activities,industrial activities,etc).


CAUSES OF SOIL EROSION IN India :

1)Heavy population pressure on land: - forest cover as low as 20.55% of total area – population continues to rise at a rapid rate – more forests are destroyed – heavy pressure on land.

2)Nature of Rainfall:-
receives 80 to 90 per cent of rainfall in the monsoon season. – heavy downpour during during monsoon months causes floods. - remaining months – droughts – these affect soils.
3)Overgrazing :–
 number of domestic animals, esp cattle highest in world – cattle freely graze in open lands making them bare of vegetation-winds carry away dry soil particles – Rajasthan
4). Bad farming techniques :–
plough fields in traditional ways – small size of holdings, absence of terracing, contour cultivation, crop rotation, improper use of manure have caused erosion
5) Topography: –
North –Eastern parts of India, Shiwaliks and the hilly regions in south India are affected by soil erosion because of steep slopes and heavy rainfall. During heavy rainfall, soils are washed away by running water down the slope.
6) Deforestation:
 destruction of forests for cultivation – cutting of trees exposes the soil to water and wind which leads to soil erosion.

 SOIL CONSERVATION :
PREVENTION OF SOIL EROSION :

1.Terrace Farming:
On hilly slopes, terraces act as bunds and prevent the soil from being washed away.


2. Contour ploughing :
Ploughing along contourson a slope prevents soil being washed away by rainwater or by surface run off. Contours act like bunds.
Terraces are levelled into step like small fields with even slope.


3)Afforestation:
planting of trees along the edges of the fields, the waste land and on steepy slopes to prevent soil erosion as wellas to enahnce the capacity of the soil to retain water.
4) Shelter Belts:
Farmers plant trees in several rows to check wind erosion. Known as wind breaks.

5) Strip cropping:
Crops are grown in alternate strips of land to check the impact of the winds.


6) Construction of dams:


Rivers cause soil erosion. Dams are built in the upper course of rivers to control erosion of soil. 
This would check the speed of water and thereby save soil from erosion.

7) Ploughing Gullies:
The gullies made in the soil are plugged with deposition of silt during heavy rains.

8) Shifting or Jhuming or slash and burn type of agriculture should be banned.



2 comments:

  1. Excellent sir. You made the topics easy with this posts. Thank u

    ReplyDelete
  2. Thank you sir .

    ReplyDelete