Types of Soil: Soils in India are divided into 8 major groups as per the All India Soil Survey Committee set up in 1953 by the ICAR – Indian Council of Agricultural Research.
One valuable and important resource for each and every human being is soil, a mixture of organic materials and rock debris. Soil develops on the surface of the earth. Time, relief, parent material, vegetation, climate and various life forms are the major factors that determine characteristics of soil. Humus, air, particles of minerals and water are major constituents of soil. Soil horizon is a layer that runs parallel to the crust of soil. Physical characteristics of the soil crust vary from the layers above and beneath.
Depending upon their external features and inherent characteristics including content of moisture in the soil, location, composition, texture, slope of land and color, accordingly soils are classified.
A comprehensive study of soils was done by the Soil Survey of India, established in the year 1956. The different types of soils are
Alluvial soil also called as depositional soil, is found in the plains of Gujarat, Haryana, Punjab, Jharkhand, UP, Bihar etc. Rich in lime and potash, a large variety of Kharif and Rabi crops like jute, cotton, wheat, sugarcane, rice etc are grown in this soil. Around 40% of the total land area in India is covered by alluvial soils. River streams transport and deposit this soil which is rich in potash, normally. Alluvial soil of 2 types is found in the Upper and Middle Ganga plain. Bhangar – is an older alluvium system deposited away from flood plains and Khadar is new alluvial soil deposited each year, by floods. Alluvial soil comes in ash grey to light grey in color and in nature varies from clayey, loamy and sandy.
2. Laterite Soils
Laterite Soils are generally infertile, poor in nitrogen, calcium, organic matter, phosphate but enriched in potash and iron oxide. This soil is saline and sandy in nature and is found in regions of high rainfall and high temperature in regions like Madhya Pradesh, Karnataka, Assam, Kerala, hilly areas of Odisha and Tamil Nadu.
Tropical rains cause increased leaching away of silica and lime from the soils making them the rich in aluminum and iron oxide. This red to brown color soil is used widely in construction industry to make bricks.
3. Black Or The Regur Soil
Black (Regur) soil also called the Black Cotton Soil is found in the Deccan Plateau – Maharashtra, Tamil Nadu, Madhya Pradesh, Gujarat and Valleys of Godavari and Krishna. This impermeable, deep and usually clayey soil has high capability to retain moisture and hence useful for cotton crops. The soil varies from grey to deep black and is rich in alumina, lime, magnesia, iron and potash.
4. Desert and Arid Soils
Arid Soil found in lower horizon has increased calcium content downwards and is occupied by ‘Kankar’ layers. Typically developed in western Rajasthan, arid soil has poor content of organic matter and humus.
5. Yellow and Red Soils
The Yellow and Red soils generally have poor humus, phosphorous and nitrogen content. The coarse grained soil found in the upland areas is less fertile while the fine-grained yellow and red soil is generally fertile.
The red soil has reddish color as iron is widely diffused in the metamorphic and crystalline rocks. When found in hydrated form it develops yellow color. Red soil develops in low rainfall areas on crystalline igneous rocks, in the southern and eastern parts of the Deccan Plateau.
6. Saline Soils
Saline soil is deficient in calcium and nitrogen and contains more salt due to the poor drainage system and dry climate. This soil is infertile and does not support vegetation as it contains magnesium, sodium and potassium in larger proportion. It is found in swampy and waterlogged areas, arid and semi-arid regions, like the Sunderban areas of West Bengal, deltas of the eastern coast and western Gujarat.
7. Forest Soils
Forest soils are found in forest regions where rainfall is available in sufficient quantities. Soil is a living system, which develops, decays, degrades and if treatment is administered properly and in time, it responds well, just like other organisms.
8. Marshy And Peaty Soils
Peaty soil is normally black in color, heavy and found in southern part of Uttaranchal, Tamil Nadu, northern part of Bihar, Odisha and coastal areas of West Bengal. The soil is formed in areas with high humidity and heavy rainfall. Dead organic matter accumulates in large quantity, is enriched in organic and humus content and forms peaty soil.
2.Characteristics of Soil
Soil is a mixture of humus, organic materials and small particles of rock which develop on the surface of the earth and support plant growth. Right from the ancient period, soil was classified into fertile (Urvara) soil and sterile (Usara) soil.
In modern times characteristics of soil were classified on the basis of moisture, color, texture, etc. Soils of different types and their characteristics were studies in 1956 by the Soil Survey of India. A lot of studies were done on soil in India by the National Bureau of Soil Survey and the Land Use Planning Institute which is under the control of Indian Council of Agriculture Research.
Different types of soil is found in India, including Alluvial Soil, Red Soil, Black Soil, Arid Soil, Laterite Soil, Saline Soil, Peaty Soil, Forest Soil, Sub-mountain soil and Snowfields.
Alluvial soil is a light grey to ash grey, highly fertile soil found in the river valleys, northern plains, estuaries and deltas. It is silty loam, sandy or clayey and contains organic matters, lime and humus and covers an area of 143 sq.km and is available in about 43% in India. Streams, rivers, etc, transport and deposit this depositional soil. The Narmada-Tapi plain and Indus-Ganga-Brahmaputra plain etc are examples of areas having alluvial soil. Alluvial soil is of two types, Khadar – new alluvium and Bhangar –alluvium. It is poor in phosphorous, rich in potash and suitable for cultivating oilseed, wheat, pulses, rice, sugarcane, maize, etc.
2. Red Soil
Red Soil is a sandy to clay and loamy soil found in low rainfall regions. It is friable and porous in structure and deficient in manganese, lime, humus, phosphate, potash and nitrogen. Ferric oxide present in it imparts the red color to it. Its lower layer is yellow or reddish yellow in color. It is suitable for cultivating potato, wheat, oilseeds, tobacco, pulses, cotton etc.
3. Black Soil
Black Soil also called as Regur Soil is a mature soil, with high capacity for retaining water. When wet it swells and sticks and it shrinks and develops wide cracks when dried. Black Soil is found in the Deccan and is best for cultivating cotton. This soil with clayey texture is light black to deep black in color, rich in magnesium, iron, aluminum, lime, potassium and calcium. It is deficient in organic matter, phosphorous and nitrogen.
4. Laterite Soil
Laterite soil is formed when silica and lime is leached away from the soil. Iron oxide gives it the red color. This soil formed due to high leaching becomes soft when wet and on drying it becomes hard. The name Laterite comes from the word ‘Later’ meaning Brick. It is found in regions with high rainfall and high temperature. Laterite soil is rich in aluminum and iron and deficient in potash, humus, nitrogen, lime and potassium. Cashew, rice, sugarcane and ragi are mainly cultivated in Laterite Soil.
5. Arid or Desert Soil
Arid soil is a sandy and red to brown colored soil with high salt content. It is deposited mainly by activities of the wind and found in arid and semi-arid conditions. It is high in impure calcium carbonate contents which restricts water infiltration. It lacks humus and moisture.
6. Peaty or Marshy Soil
Peaty Soil is a black colored and heavy soil. It is found in regions with high humidity and heavy rainfall. It makes the soil alkaline due to presence of humus and dead organic matter in large quantities.
7. Forest Soil
Forest Soil is found as a continuous cover on the surface of the earth except on the steep slopes. The soil is acidic and has less content of humus in it. Forest soils are affected in various ways including geomorphic, biotic and climatic factors of a particular place.
8. Mountain Soil
Mountain Soil with low acidic and low humus is found in the mountainous regions. Variation in temperature, snow, rain etc caused mechanical withering to form this soil. Mountain soil is found in Sikkim, Andhra Pradesh, Jammu and Kashmir and Assam. Around 8% of India’s land area is occupied by mountain soil. The soil is suitable for growing plantation crops like spices, coffee, tea and tropical fruits. Though rich in humus, it is deficient in lime phosphorous and potash.
3.Classification Of Soils Of India
Soils in India are divided into eight different categories, as per the ICAR – Indian Council of Agricultural Research. They are alluvial soils, laterite soils, black cotton soils, desert or arid soils, forest or mountainous soils, marshy and peaty soils and alkaline and saline soils.
Alluvial soil is found in abundance in the foothill regions and in river valleys, coastal plains and the Indo Ganga-Brahmaputra plain. Around 24% of the land surface is covered by alluvial soil. The proportion of clay, loam and sand in the soil varies. Alluvial soil is of 2 types, Khadar and Bangar. Bangar is an older alluvium containing calcium carbonates and pebbles. Khadar is a new and a more fertile alluvium deposited every year by rivers.
Alluvial soils are deficient in humus and nitrogen but rich in carbon compounds, potash, lime and phosphoric acid. The soil can be yellowish, light brown or grey in color.
Black Cotton Soils
Black Cotton Soil also called Regur soil is formed by erosion and weathering of lavas. This dark grey or black soil containing aluminum and an iron compound called Titaniferrous Magnetite is found in the Deccan lava plateau and very suitable for dry farming. Montmorillonite mineral is present in the soil due to which it shrinks on drying and swells on wetting. The capacity of retaining moisture in the oil is high making it suitable for growing citrus fruits, cotton, sunflower and coarse grains. The soil is not favorable for heavy irrigation. Regur soil is rich in magnesium, lime, calcium, aluminum and iron but deficient in phosphoric acid, humus and nitrogen.
When metamorphic and crystalline rocks disintegrate in regions with heavy rainfall, red soil is formed. These coarse grained and are porus rocks are rich in ferro magnesium minerals. The red color is imparted due to presence of excessive iron oxide in the rocks. Capacity of retaining moisture is low, making the soil less fertile due to which it needs frequent and heavy irrigation for the purpose of agriculture.
The soil is rich in aluminum, magnesium and iron compounds and lack lime, phosphoric acid, nitrogen and humus.
It is found as unconsolidated soil in the higher land and as clay in low lying areas. Potato, groundnut and bajra is grown in the higher parts and vegetables, ragi and rice in the low lying areas.
Due to washing away of silica and lime, laterite soil is formed in regions of heavy rainfall. By nature this residual soil is formed under typical monsoonal conditions. This soil is found in regions with humid climate including the top of Eastern Ghats, Deccan Plateau, Malabar & Rajmahal hills, Mysore, Western Ghats and Assam. Laterite soil is formed by a leaching process in which siliceous compounds in the soil are washed away by sloping terrain and hot climate, which makes the soil poor in siliceous compounds. Fertility of the soil is poor and best suited only for pastures and bushes. Quality of the soil is improved with fertilizers to cultivate plantation crops like ragi, coffee, cashew nut, coconut etc. Rich in aluminum and iron the soil is deficient in potash, phosphoric acid and nitrogen.
Desert And Arid Soils
Desert and arid soil is light in color and found in semi-arid and arid regions in Rajasthan. Phosphorous and high soluble salts are present in high quantities but lacks in nitrogen and carbon compounds. Crops like bajra and Jowar are grown in the soil and also in regions like Sri Ganganagar of Rajasthan to grow cotton and wheat.
Forest Or Mountainous Soils
Mountain soil contains pebbles, stone pieces and kankars. Depending upon the climate, this soil differs and is distributed in the Nilgiris, Himalayas, Satpura, Vindhyas and other mountains in India. Decomposed humus is present in it in excessive quantities making it acidic in nature. When used for agricultural purposes, fertilizers are added to the soil. More humus is present in the soil found in mountainous regions. Accordingly it is best suited for growing barley, different fruits, maize, wheat, etc. The soil is poor in lime, phosphoric acid and potash but enriched in humus and organic matter.
Alkaline And Saline Soils
Alkaline and saline soil is found in arid and semi arid regions of Uttar Pradesh, Tamil Nadu, Rajasthan, Maharashtra, Punjab, Bihar and Haryana. Also known as Usar, Kallar and Reh in the local areas, this infertile and non agricultural soil is found in patches. Its capacity to hold water is poor and it is deficient in nitrogen. When gypsum and lime is mixed in it and treated, then crops like tobacco, sugarcane, wheat, rice, cotton etc can be grown. Salinity in the soil increases with excessive amounts of magnesium, sodium and calcium.
Marshy And Peaty Soils
In the case of marshy and peaty soils, organic matters get accumulated in large quantities for long periods under water-logged conditions. The organic matter gives marshy soil it’s black or dark grey color. The soil also called Kari, is found in patches in coastal regions like Kerala, Orissa, Tamil Nadu and West Bengal. Though this soil has high salinity, it is deficient in potash and phosphate and hence not suitable for agriculture.
4.Problems of Indian Soils
High fertility soils in wide varieties are found in India. However with various human and natural activities it is getting degraded. Soil degradation or soil fertility loss results in low productivity in crops and plantation, loss of biodiversity, increased production costs, scarcity of food, low income, etc. India faces a major concern of food security, low production of food due to problems of soils. This problem can be best overcome with soil conservation.
Soil degradation is caused by a number of factors including:
1 Erosion of Soil
3. Low soil fertility
4. Shifting cultivation
5. Water logging
1.Erosion Of Soil
Soil erosion is mainly caused by agents like water, wind, glaciers and waves. Human activities and natural events both cause erosion of soil. Rajasthan and Madhya Pradesh are two states largely affection by erosion of soil in India.
Soil erosion caused by water is classified into:
• Rill Erosion
Rill in land is caused by heavy flow of water.
• Sheet Erosion
Just like a sheet, the top soil is removed in a uniform manner.
• Gully Erosion
Enlargement of the Rill takes place to form Gullies and in the process the land gets disordered. (an example is the Chambal Valley)
Result Of Soil Erosion
• Top soil loses its fertility
• Rivers dry up
• Soil erosion lessens content of nutrients in soil
• Frequent floods and drought
• Habitat and vegetation is lost
• Reduction in water level underground
• Culture and economy gets adversely affected
• Gully erosion leads to formation of natural hideouts (The popular criminal hideouts have been in the Chambal Valley)
2.Salinity Of Soil
• An example of low alkaline or low saline soil is Rajasthan, which is a low rainfall region.
• Soil becomes saline when sea water flows into the land area.
• Calcium carbonate present below the soil does not allow water to pass, thus causing water logging. Soil containing salt, fills us the whole land area with salt.
3.Low Soil Fertility
• Land becomes unfertile with cropping after cropping
• Excessive use of chemical pesticides and fertilizers
• Crop rotation is done in an unscientific manner
• Even if there is adequate supply of nutrients and irrigation, the soil production is not enough.
• Fertility of soil is affected most in Uttar Pradesh, Haryana and Punjab.
Ways To Improve Soil Fertility
• To retain fertility, soil should not be cultivated for long periods.
• Cultivation of leguminous plants at regular intervals
• This cultivation method is a kind of slash and burn method practiced in India’s north eastern states, mainly.
The forest is slashed and burnt after crops are reaped, then cultivation is done on another land while the burned land is kept as it is for a period of around 2 to 3 years without cultivation. The burned land was left uncultivated for 1 to 2 decades, in the earlier periods.
• Shifting cultivation leads to loss of habitat for wild animals, pollution in environment, major deforestation, etc. Burning forests leads to erosion of soil and gradually degradation of soil.
• Water logging leads to water saturation.
• Water logging does not allow normal air circulation leading to decline of oxygen in the soil.
• Land becomes waterlogged if the drainage system is not proper on land
• Water logging can be best reduced by construction an appropriate drainage system to enable proper flow of water from the land.
5.Consequences Of Soil Erosion
Soil Erosion is removal or weathering away of soil by, tillage, wind and flowing water. The process of erosion and soil formation is continuous. Between both these processes there is a balance. At times, in a few years’ time, the entire layer of soil is removed by human or natural factors.
Soil erosion’s effects go beyond the loss of fertile land. Various chemicals and pesticides get trapped within the soil with soil erosion leading to excessive sedimentation as well as pollution in rivers and streams. Waterways get clogged, the number of different water species and fish gradually decline. Once the soil breaks apart and land gets degraded, its capacity to hold water lessens which in turn makes flooding worse.
Over time the soil becomes deficient in nutrients and poor in quality due to agricultural tilling and abusive farming. Organic matter depletes from the soil with soil erosion making it less suitable for crop plantation, crop harvesting and vegetation production the natural way.
Poor quality of water and pollution
A process called sedimentation results with gradual soil erosion. Minerals and rocks from soil separates, lodges in rivers and streams and gets deposited at other places. Rivers and streams get contaminated with pest control agents and fertilizers spread on soil. The quality of water reduces due to the presence of water pollutants. If pollutants are not removed before it is consumed then water is not suitable for consumption purposes.
Sunlight gets into the sediment causing excessive algae growth. Oxygen in huge amounts is absorbed by the high levels of algae leading to death of fish and other aquatic animals.
Structural And Mudslide Issues
Mudslides are caused by soil erosion which has an impact on structural integrity and stability of roadways and buildings. Roads and building located on path of the slides, besides structures are affected by mudslides.
The energy and force of heavy rains, makes the fine sand, organic matter, stilt and clay spill off the slopes and hillsides, thus causing mudslides. The draining off is so fast that the surface is not able to trap or reabsorb soil erosion.
Flooding And Deforestation
Room is created for farming purposes and creating cities by removing trees, which is called deforestation. Deforestation erodes the soil away. Soil is held in place by trees and when they are removed, heavy rains push rocks, sand and loose soil to rivers and streams. This results in undesirable sedimentation. It begins to flood when sediment in heavy layers prevents rivers and streams from flowing smoothly. The sediment traps extra water when snow melts and in the monsoon season, as except land, the water has no other place to flow into.
Degradation Of Soil
Practicing poor methods of agriculture and farming takes away nutrients from the soil leading to erosion of soil. Content of nutrients in the soil reduces with outdated tilling and excessive irrigation. The soil is not suitable for cultivation and natural vegetation. Fertility can be improved by deliberately leaving organic matter in the soil.
Soil erosion can be prevented by adopting measures of soil conservation, including leveling uneven land, bunding, building bunds across gullies, contour terracing and growing vegetation and grass on land. Such measures are best to consider in areas when erosion is not on large scale in areas like Punjab, Uttar Pradesh, the semi-arid tracts of the peninsula and some parts of Gujarat, Haryana and Madhya Pradesh. Schemes for large scale reclamation have been carries out in these states. Steps taken under these schemes include limiting overgrazing by animals, leveling of surface areas, building bunds across gullies and afforestation.
Better techniques in farming are taught to adivasis. Shifting cultivation is adopted in tropical forest areas including Orissa, Andhra Pradesh and Madhya Pradesh.
Soil conservation is done by various methods
Rotation Of Crops
Growing the same crop in the same soil for more than 24 months in continuation is not recommended as one particular nutrient is used up completely by the crop. Growing alternate crops is best as it maintains fertility of soil in the most natural way.
Sections are made on slopes, in a series of terraces for cultivation. The terrace level ground has an outer wall at the edges which holds the soil and reduces rainwater flow, down the slope.
Alternate strips are created, parallel to one another to cultivate crops. While some strips remain unsown, crops are grown in the remaining strips. Accordingly crops are harvested at different times of the year. Thus no land area is kept exposed or bare. Water absorption is high in soil wherever tall growing crops are grown.
Management Of Water
Crop yields, bacterial activity can be improved by regulating the water amount in soil aeration. Besides this, swamps and desert regions can be used for agricultural purposes.
Creepers are inter-planted between the young trees are planted so that they spread and make a protective cover to prevent the soil from erosion. Precaution should be taken that the young trees and cover crops do not outgrow each other.
Soil is kept fallow so that decayed matter and vegetation improves nutrient content in the soil. General structure and sub-soil moisture of the soil improves with fallowing. In temperate regions, winter fallow is done, after the harvest after which cultivation is initiated in spring once the top soil is weathered by frost and snow.
Land is kept unused in semi arid regions. However it is mulched and ploughed to reduce evaporation and build sufficient moisture. Every few years, a crop is grown.
Ploughing is done on natural contours of furrows, ridges and hills, which breaks down water flow down the slopes. In this way lesser soil is lost, gullies are not formed and run-offs reduce due to which plants get adequate water. Plantation of small grains and row crops is done in the contours for plants to absorb more rain water and minimize erosion.
Diversification Of Crops
Diversifying crops is a type of crop rotation that helps in minimizing the danger of relying on any one crop, especially when commodity prices across the world may fall. Land of all types is used in the advantageous method of crop diversification.