Soils in India

Soil is an important natural resource that covers much of the earth’s land surface and on which all life depends as a source of food directly or indirectly.

Soil formation differs according to the effect of various environmental factors which include kinds of present material, climatic conditions, the most important aspect of which is weathering, then living things such as plants & animals, & finally the surface relief & drainage. Soils of India may be broadly divided into two groups:

i) Residual Soil: These soils are generally found in areas where transportation of weathered material has not taken place. After the washing away of soluble minerals, decomposed organic matter has altered the original fragmented rocks to soil. This type of soil is mostly found in peninsular region.

ii) Drift soil: This is another variety, mainly laid down by flowing water. Sedimentation of regular intervals is responsible for this type of soil formation. Obviously, North Indian plain is the classic example of this type of soil formation.

Considering variation of texture, structure, color, constituent minerals, the soils of India, are generally sub-divided into sight broad groups. These are :

i)          Alluvial Soil                 v)         Arid Soil

ii)         Black Cotton               vi)         Laterite soil    

iii)        Red Soil                      vii)       Peaty soil

iv)        Forest soil                   viii)      Saline or Alkaline soil                                                       

Alluvial Soils

• are the most extensive, covering nearly 40% of the total area which consists of river basins, deltas & coastal regions.
• are formed by the denudation of different types of rocks & the deposition of sediments by river.
• may be classified as Bangar and Khadar, Bangar is the older soil found about 30 m. above sea by level in river terraces. It is light grey in color, less fertile & consists mainly of calcareous clay. Khadar or new soil is found in the lower beds of the valley through the river meanders. It is non-porous, clayey & loamy, is more fertile as it is replenished by floods.
• Alluvial soils are deficient in organic matters & nitrogen & tend to be phosphoric.
• Varies greatly in texture from coarse to fine.
• This soil region encompasses greater part of fertile agricultural field in India. It is found in Punjab, Haryana, U.P., Bihar, Bengal, Orissa, Rajasthan, the coast of Gujarat, the Brahmputra valley & the coastal strips of Peninsular India.

Black Cotton Soil or Regur Soil

• Is of volcanic origin. It consists of lava soil due to the disintegration of basalt.
• It is called ‘Black Cotton Soil’ because cotton thrives on it.
• It occurs mainly in the Deccan trap comprising the greater part of Gujarat & Maharashtra. It is also found in parts of M.P., North Karnataka and a small area of Southern Tamil Nadu.
• These soils are usually fertile, are deep, fine grained & varying in color from black to chestnut brown.
• Are rich in iron, potash, lime, calcium, alumina, magnesium, carbonates & humus, but it is deficient in phosphate nitrogen & organic matter.
• Are moisture retentive & very sticky when wet, but when dry, harden & form cracks.
• Cotton, millets especially jowar, wheat, oilseeds, sugarcane, tobacco, gram, fruit & vegetables are grown as rainfed crops in these regions.

Red Soils

• are derived from the weathering of crystalline & ancient metamorphic rocks - have a slight mixture of clay & sand.
• redness is due mainly to the high concentration of iron oxides.
• are deficient in nitrogen, lime, phosphoric acid and  humusare rich in potash,
• Porous friable but not retentive of moisture.
• These soils respond well to irrigation and become productive on adding fertilizers.
• extensively occur in theChhota Nagpur Plateau as also in large parts or Karnataka, Tamil Nadu, North-eastern M.P., Andhra Pradesh & Orissa. These soils are second only to alluvial soils in the area covered by then.
• Wheat, rice millets, cotton, sugarcane, pulses are grown if fertilizers & irrigation are used.

Laterite Soils

• are due to weathering of laterite rocks caused by alternating extremes of temperature & marked wet & dry seasons.
• are formed due to intense leaching during the periods of heavy rainfall.
• are generally unsuitable for agriculture due to its high content of acidity and inability to retain moisture.
• cashew & topicco grow well on it.
• these soils occur in parts of Kerala, Goa, Tamil Nadu, Karnataka, Andhra Pradesh, Orissa, Bengal& the summits of the Western & Eastern Ghats and  Malwa Plateau.

Arid Soil

• This soil is predominant in the vast dry tract of North-West India where annual precipitation is very low. Rajasthan, Punjab, &Gujarat are covered partly by this soil.
• due to high evaporation rate & lack of vegetation, salt content is quite high and humus content is very low.
• but due to less leaching, mineral accumulation is high.

Forest Soil

• dense growth of conifer forests, high rate of denudation has favoured greatly for the soil formation in the Himalaya and other high altitude areas.
• are found in the slopes of mountains & hills in the Himalayas, Sahyadris & Eastern Ghats.
• rich in humus content.
• used for plantations of tea, coffee, spices & fruits.
• are deficient in potash lime & phosphorus.

Peaty Soils

• In coastal areas, high salinity & heavy organic matter concentration leads to formation of peaty soils.
• frequently visible along the eastern & western coasts of India.

Alkaline Soils

• many regions of North India have experienced massive accumulation of salt through intense irrigation. This has resulted in deterioration of soil condition in Punjab, Haryana, Gujarat and Bihar.
• alkali content is high & nitrogen &  organic matter contents are low.
• locally these soils are known as Ushar in North, Kalar in West(inPunjab also)& Chopan in South-West.

Problem of soil erosion

While some erosion in the soil occurs naturally everywhere, the situation in Indian is worsened by:

• Monsoonal rainfall pattern
• rapid deforestation and loss of vegetative cover, and
• improper farming/cultivation methods in different parts of the country (like jhum, hill slope farming, etc.)

Types of Erosion

1. Normal or geological erosion, which occurs everywhere

2. Accelerated Soil Erosion accelerated by anthropogenic factors

3. Wind Erosion mostly prevalent in the Thar desert

4. Water Erosion

5. Rain erosion

6. Sheet erosion mostly in the desert regions

7. Rill Erosion prevalent in the Chhos region of Punjab

8. Gully Erosion has given rise to badland type of topography found in Chambal, Sabarmati, Mahi valleys, and the catchments of Mayurakshi, Kangasbatti and the Gomti.

Consequences of Soil Erosion

1. Loss of fertile (plant nutrient rich) topsoil cover reduces productivity and capacity to support vegetation. This develops into a positive feedback process causing further and accelerated soil erosion.

2. Reduction of water infiltration into ground thus affecting soil moisture and ground water resources.

3. Reservoirs and canals (as well as rivers) get silted and lose their water holding/carrying capacity.

Zones of Soil Erosion in India

Some measures to conserve Soils

1. Afforestation of the regions affected by soil erosion.

2. Afforestation of deforested regions( reforestation).

3. Plantation of fast-growing species of trees in the flood prone regions, which will reduce the intensity of Flood and erosion in the near future.

4. Erection of dams and barriers on the slopy lands and against the fast flowing rivers. Their construction will reduce the speed of water, resulting in the prevention of gully erosion.

5. Control of irrational grazing.

6. Contour ploughing should be done.

7. Agricultural land should never be left fallow. If there is need to leave the land fallow for a certain period adequate bunding should be done.

8. To conserve soils it is also necessary that their fertility should be retained. This can be done by adequate use of manures and adopting crop rotation.

9. The alkaline soil should be reclaimed[1]. It will help increase productivity.

Soil Conservation and Management

As population pressure increases the per capita soil availability is decreasing even while the intensity of soil degradation processes is increasing. Physical and chemical constraints on soil production potential are being accentuated by improper management practices. A research programme has been undertaken to identify the extent and degree of these constraints and to evolve appropriate corrective and preventive measures. Its objectives are:

A. to minimize the process of erosion and land degradation.

B. to restore degraded lands

C. to ensure rebuilding of internal fertility of soil through organic recycling particularly in resource poor regions.

D. to enlarge effective productive exploitation zone to deeper soil profile by adopting mixed and companion farming system.

E. to increase aggregate biomass production, and

F. to generate employment through continuous adjustments in optimum land use planning.

Programmes taken up at the national level provide an over-all perspective of problems like water and wind erosion, degradation through water logging, salinity, ravines, torrents, shifting cultivation and coastal sands. The important central schemes have been directed towards checking premature siltation of multipurpose reservoirs, mitigating flood hazards in productive plains, resettling of shifting cultivators and restoring degraded lands.

Recently government began providing soil health cards to the farmers highlighting the physical and chemical qualities as well as deficiencies of their soils.

Soil Salinisation and Alkalinisation

Soil Salinisation refers to the accumulation of salts on the topsoil. Salinisation is a natural process in arid and semi arid regions, where evaporation exceeds precipitation. It is man made as well, particularly in canal-irrigated tracts of Western UP, Haryana, Punjab and Rajasthan. Canal irrigation in the alluvial formations cause seepage of canal water. Seepage raises the water table. If more water is applied to the fields the water table comes to the surface causing water logging. Water logging has dissolved salts from the soil. If water evaporates, the dissolved salts remain on the field, forming a thin film of salt on the surface.

The saline soils contain free sodium and chlorine, but when sodium ions predominate in the soil solution with additional presence of carbonates then the soils are alkaline.

Effect

1. Lowering of yields

2. Choice of crops are limited

3. Quality of fodder is lowered

A Centrally sponsored scheme of reclamation of alkali soils was taken up in Punjab, Haryana and Uttar Pradesh during the Seventh Five Year Plan. The scheme was further extended to the States of Gujarat, Madhya Pradesh improving physical conditions and productivity status of alkali soil for restoring optimum crop production. The major components of the scheme include assured irrigation water on farm development and works like leveling, bunding and ploughing, community drainage system, application of soil amendment, organic manures etc.

Another project for alkali land reclamation and development has been taken up U.P. and Bihar with the help of C.S.C. control of shifting cultivation.

Control

1. Drainage of excessive water

2. Lining the canals

3. Minimise the use of water application

4. Treating the soil with lime and gypsum

5. Flushing the salts by flooding the fields of drainage is good

Soil Laterisation

Soil Laterisation takes place in that region where the climate is of alternate wet and dry type. During the rainy season, the torrential rains leach the topsoil of its nutrients and other materials in the lower horizon. In summer when the evaporation is very high all the nutrients along with iron and aluminum are drawn on the top surface by capillary action. This forms a very hard brick like layer. This process is particularly prevalent in those regions where jhum cultivation is practised. Jhuming denures the top layer of its vegetation cover allowing greater leaching during the rain season. In the summer the topsoil is baked by the blazing Sun forming laterite. Thus, these types of soils are being constantly formed in regions of shifting cultivation.