This system of classification is based on the constitutional traits of soil color and resource importance.
According to the United States Department of Agriculture's (USDA) Soil Taxonomy, the ICAR has also categorized Indian soils according to their nature and characteristics:
1. Alluvial Soils
• The Indo-Gangetic-Brahmaputra Rivers' silt deposition is the primary cause of alluvial soil formation. Some alluvial deposits are created by wave action in coastal areas.
• The parent material is composed of Himalayan rocks. Therefore, these soils' parent material had a transportable origin.
• The largest soil group, they cover over 15 lakh sq. km, or roughly 46% of the total area.
• They provide the most fertile agricultural lands, which in turn support more over 40% of India's population.
Specifications of Alluvial Soils
• Due to their recent origin, they are immature and have poor profiles.
• Sand is the predominant kind of soil, while clayey soils are also widespread.
• In drier areas, they range from loamy to sandy loam, and near the delta, they become clayey loam.
• Rare are soils with pebbles and gravel. Some areas along the river terraces have kankar (calcareous concretions) beds.
• Because it is loamy (equal parts sand and clay), the soil is porous.
• Good drainage and other agriculturally beneficial conditions are provided by porosity and texture.
• The frequent floods continuously replenish these soils.
Chemical characteristics of alluvial soils:
• In general, nitrogen makes up a small fraction.
• Potassium, phosphoric acid, and alkalies are present in a sufficient ratio.
• There is a variation within a wide range of proportion between iron oxide to lime.
Indian Alluvial Soil Distribution
• Occur All along the Indo-Gangetic-Brahmaputra plains, with the exception of a few spots where the top layer is obscured by desert sand.
• They also exist in the Krishna, Cauvery, Godavari, and Mahanadi deltas, where they are known as deltaic alluvium (coastal alluvium)
• There are some alluvial soils in Gujarat's Narmada and Tapi valleys as well as its northern regions.
Alluvial soil crops
• They are best suited for agriculture since they often have flat, uniform soils.
• They respond well to canal, well, and tube-well irrigation and are best suited to irrigation.
• Rice, wheat, sugarcane, tobacco, cotton, jute, maize, oilseeds, vegetables, and fruits are among the magnificent crops they produce.
Alluvial soils' geological classifications
Geologically, the Great Indian Plain's alluvium is separated into younger or newer khadar soils and older bhangar soils.
• The Shiwalik foothills are the location of the 8–16 km wide bhabar belt. It is the northernmost, most permeable section of the Indo-Gangetic plain.
• Alluvial fans are created when rivers carrying sediment from the Himalayas descend and deposit it along the foothills. The bhabar belt was created by the fusion of these alluvial fans, which are frequently pebbly soils.
• The most distinctive quality of bhabar is its porosity. The alluvial fans' porosity is caused by the massive deposition of pebbles and rock fragments throughout them.
• This porosity causes the streams to dry up once they get to the bhabar area. Therefore, except from during the rainy season, the area is identified by dry river systems.
• To the south of Bhabar, running parallel to it, lies the Terai, a narrow region that is poorly drained, moist (marshy), and heavily forested (15–30 km wide).
• In this belt, the Bhabar belt's subsurface streams reappear. It has silty soils and is a lowland marsh.
• The terai soils are low in phosphate but high in organic matter and nitrogen.
• Although thick grasses and woodlands typically cover these soils, they are good for a variety of crops, including wheat, rice, sugarcane, jute, and others.
• A variety of species can find shelter in this heavily forested area.
• Older alluvium along the river banks, known as the Bhangar, has formed terraces that are higher than the flood plain (about 30 meters above the flood level).
• It is often black in colour and has a more clayey composition.
• There are beds of "Kankar" lime nodules a few metres below the terrace of the bhangar.
• The flood plains along the river banks are formed by the Khadar, which is made up of more recent alluvium.
• Almost every year, the banks are flooded, and each flood deposits a fresh layer of alluvium. They are the Ganges' most fertile soils as a result.
• They are less calcareous and carbonaceous, leached, and sandy clays and loams (less kankary). River floods create a new layer of alluvium practically every year.
Areas with alluvial deposits and rain
Above 100cm: suitable for Paddy
Between 50 and 100cm: suitable for Wheat, sugarcane, tobacco, and cotton
Less than 50 cm – suitable for coarse grains (millets)
2. Black Soils
• Weathering caused these basaltic rocks, which first appeared during fissure eruption during the Cretaceous epoch.
• Volcanic rocks that originated in the Deccan Plateau are the source of the majority of the black soil (Deccan and the Rajmahal trap).
• Gneisses and schists make up the parent material of Tamil Nadu. While the latter are often shallow, the former are appropriately deep.
• High temperatures and little rain fall are prevalent in this area.
• Therefore, it belongs to a category of soils that is typical of the hot and arid areas of the Peninsula.
• 15% of the area is the extent
• Basalt contains titani-ferrous magnetic chemicals that give the rock its dark color.
Black soil characteristics
• A typical black soil has a high clay component of 62 percent or more and is highly argillaceous. Geology (of rocks or sediment) consisting of or containing clay).
• On general, dark soils in the uplands are less fruitful than those in the valleys.
• The black soil holds moisture quite well. When moisture builds up, it swells significantly. Working on such soil during the rainy season requires a lot of effort since it becomes quite sticky.
• When the moisture evaporates in the summer, the earth contracts and develops wide, deep fractures. Lower layers still have the ability to hold moisture.
• The soil has exceptional fertility and the cracks allow for adequate soil oxygenation.
• It becomes blocky and develops cracks when it dries out.
• Self-Plowing Capability
Black Soil Color
• The parent rock's black components plus a trace amount of titaniferous magnetite or iron are what give the material its dark color.
• Crystalline schists and simple gneisses are the source of the black color in Tamil Nadu and some areas of Andhra Pradesh.
• In this group of soils, different shades of the color black, including deep black, medium black, shallow black, and a combination of red and black, may be found.
The Chemical Makeup of Black Soils:
• 10% of alumina, 9%–10% of iron oxide, 6%–8% of lime, and 4%–6% of magnesium carbonates,
• Phosphates, nitrogen, and humus are insufficient, and potash levels are variable (less than 0.5 percent).
• Humus, nitrogen, and phosphorus levels are lacking whereas iron and lime content is abundant.
Availability of Black Soils
• It can be found in India's Deccan lava plateau.
• Maharashtra, Madhya Pradesh, and portions of Karnataka, Telangana, Andhra Pradesh, Gujarat, and Tamil Nadu make up 46 lakh sq. km (16.6 percent of the total area).
Crops in Black Soils
• Cotton crops grow best in these soils. These soils are therefore referred to as regur and black cotton soils.
• Along with wheat, jowar, linseed, virginia tobacco, castor, sunflower, and millets, black soils are also used to cultivate other significant crops.
• Both rice and sugarcane are crucial in areas with irrigation facilities.
• On the black soils, a wide variety of fruits and vegetables are also successfully grown.
• This soil has been utilized for millennia to grow a variety of crops without the addition of fertilizers and manures, and there is little to no sign of fatigue.
3. Red Soil
• The second greatest area of the country is covered by this soil, which formed on Archean granite.
• The soil turns red due to the presence of ferric oxides, which are present as thin coatings on the soil particles.
• The horizon below is yellowish, and the top layer of dirt is red.
• 18.5% of the area is covered.
• Sandy to clay and loamy textures.
• The omnibus group is another name for this soil.
Red soil characteristics:
The amount of rain varies greatly. Consequently, three sorts of soil have emerged:
• Red and yellow soil- 200 cm of rainfall, northeast Quick drainage is required in India's Nagaland, Mizoram, Manipur Hills, and portions of the Malabar Coast.
• Drier plateaus of Karnataka, Tamil Nadu, Telangana, and Rayalseema have red sand soil - rain between 40 and 60 cm
• Red Alluvial Soil, which is found in river valleys, is fertile.
• Well drained soil and structure is sandy
• Potash and iron are abundant, but other minerals are lacking.
Red Soil: Chemical Composition
These soils typically lack phosphorus, lime, magnesium, humus, and nitrogen.
The location of red soil:
From Tamil Nadu in the south to Bundelkhand in the north, and from Raj Mahal in the east to Kathiawad in the west, they are primarily found in the Peninsula.
• It produces a high yield after being irrigated and fertilized with compost because of the rich mineral base.
• It encourages the growing of cotton, sugarcane, and rice.
• In drier regions, millets and pulses are grown.
• Red alluvium is well known in the Kaveri and Vaigai basins, which, if properly irrigated, are good for paddy.
• Red soil zones for coffee and rubber plantation growing have emerged in large portions of Kerala and Karnataka.
4. Formation Of Laterite Soils
In areas where the following criteria are met, this soil is developed:
1. A laterite rock or structure is required (Laterites are rich in iron and aluminium content)
2. The formation of laterite soils is better suited to seasons with alternating dry and wet spells.
• Brown in color
• Primarily made up of an amalgamation of hydrated iron and aluminum oxides.
• Nodules that contain iron oxides are present.
• Iron and aluminum are abundant, while nitrogen, phosphorus, potash, lime, and magnesium are insufficient.
• It has average humus and water-retention capabilities.
• Bacterial activity has been quite strong, and severe precipitation has caused humus to leach, resulting in a moderate to low humus content.
The following areas in the nation have laterite soil:
• In the Western Ghats, it is patchy (Goa and Maharashtra).
• In Kerala's laterite plateau and the Belgam district of Karnataka
• In the Eastern Ghats, in the states of Orissa, Gujarat, and MP's Amarkantak plateau and Jharkhand's Santhal Pangana divisions,
• It is well known for producing crops like cashew and groundnut.
• Karnataka's laterite soil is ideal for growing spices, rubber, and coffee.
5. Forest Soil/Mountain Soil Formation.
It is primarily found on mountains with steeper slopes, high relief, and shallow profiles.
• It has thin layers and poorly defined profiles and horizons.
• Fast drainage has made it susceptible to soil erosion.
• Although the humus content is acceptable and the organic content is abundant, other nutrients are insufficient.
• When sand, silt, and clay are together, the soil is described as loamy.
• They are often located above 900 meters in elevation in the Himalayas, Himalayan foothills, Western Ghats mountain slopes, Nilgiri, Annamalai, and Cardamom highlands.
• Because this soil is on a slope, it provides good air and water drainage, which is particularly beneficial to crops that need it.
• Typically used for growing rubber, bamboo, tea, coffee, and fruits, a sizable portion of the land is also used for shifting agriculture, where the soil fertility degrades after two to three years.
• The silvi pastoral farming (forest + grasses) can be supported because there is little scope for agriculture.
6. Arid (Desert) Soil
• Mostly found in dry and semi-arid regions like Rajasthan, West of the Aravallis, Northern Gujarat, Saurashtra, Kachchh, Western sections of Haryana, and Southern Punjab, this soil is deposited by wind action.
• It is deficient in moisture. Less humus is present, and although nitrogen is initially scarce, some of it is now present in the form of nitrates.
• They have little organic substance and are sandy. The amount of living microorganisms is little.
• It contains a lot of iron. The phosphorus concentration is almost sufficient and abundant in bases and lime.
• It has relatively little moisture retention capacity and little soluble salts.
• This soil produces a high agricultural yield when watered.
• These are appropriate for less water-demanding crops like guar, bajra, lentils, and feed.
• Distribution –western Rajasthan, Rann of Kachchh, in patches in south Haryana and south Punjab.
7. Alkaline And Salinity Soils
• Alkali soil has a high concentration of NaCl.
• The soil is infertile
• Reh, Usar, Kallar, Rakar, Thur, and Chopan are further names for them.
• Rajasthan, Haryana, Punjab, Uttar Pradesh, Bihar, and Maharashtra are the key locations for these.
• This soil contains sodium sulphate and sodium chloride. It works well with leguminous plants.
• Its formation and dispersal are both artificial and natural.
• Natural - Includes the Rann of Kuchchh and the Rajasthani lakes that have dried up
• In the Palaya Basin, it has appeared ( a clay basin in the midst of the desert)
• Anthropogenic - It arose in Punjab and western UP as a result of poor agriculture.
• Characteristics -Humus formation is nearly nonexistent due to a lack of moisture, humus, and live microorganisms.
8. Bog/Peaty And Marshy Soil
This dirt comes from places where it is impossible to provide appropriate drainage. It is highly salinized and abundant in organic materials. They are lacking in phosphate and potash.
• Features - Predominance of clay and muck, making it heavy
• Rich in moisture content but with higher salt content and daily flooding from high tides, it has become unproductive soil.
• No biological activity because the amount of moisture is too high.
• Distribution- It is typical of the Indian delta region.
• In addition to the delta region, it can be found in Alleppey (Kerala), Almora, and Karri along the backwaters (also known as Kayals of Kerala) (Uttaranchal),
• Jute and rice can be grown over the Bengal Delta, and large grains of rice, spices, and rubber can be grown over the Malabar region. The Indian Mangrove forests have benefited from it in certain ways.
Specifications Of Indian Soils
• Most soils are mature and ancient. Compared to the soils of the Great Northern Plain, the soils of the Peninsular Plateau are significantly older.
• Most organic components, mineral salts, humus, and nitrogen are insufficient in Indian soils.
• While mountainous and plateau regions show limited soil cover, plains and valleys have thick soil layers.
• While some soils, like those found in alluvial and black soils, are fertile, others, like those found in laterite, the desert, and alkaline soils, are not and do not produce good crops.
• Indian soils have been farmed for hundreds of years, but much of its fertility has been lost.
Issues With Indian Soils
1. Soil erosion (Himalayan region, Chambal Ravines, etc.)
2. Lack of fertility (Red, lateritic, and other soils)
3. Desertification (areas around Thar Desert, rain-shadow regions like parts of Karnataka, Telangana, etc.)
4. Waterlogging (Punjab-Haryana plain)
5. Salinity, and alkalinity (excessively irrigated regions of Punjab, Haryana, Karnataka, etc.)
6. Wasteland, overuse of soils as a result of population growth and rising living standards, and encroachment on agricultural land as a result of transportation and urban expansion.
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