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PHYSIOLOGY

SOILS IN INDIA

November 11, 2024

SOILS IN INDIA

There are seven soil deposits in India. They are alluvial soil, black soil, red soil, laterite soil, arid soil, forest and mountainous soil, and marsh soil. These soils are formed by the sediments brought down by the rivers. They also have varied chemical properties.

The Indian Council of Agricultural Research (ICAR) has classified soils into eight categories:

  • Alluvial Soil
  • Black Cotton Soil
  • Red Soil
  • Laterite Soil
  • Mountainous or Forest Soils
  • Arid or Desert Soil
  • Peaty and Marshy Soil/Bog Soil

 

PARAMETERS DATA
ALLUVIAL SOIL
Distribution Indo-Gangetic Plains, Assam, Punjab, and coastal parts of Gujarat, Goa, Kerala, Puducherry, and Andhra Pradesh.
Formation Alluvial soils are formed mainly due to silt deposited by the Indo-Gangetic-Brahmaputra rivers.
Share They are the largest soil group, covering about 15 lakh sq km or about 46% of the total area.
Physical Characteristics
  • The soil is porous due to its loamy (equal proportion of sand and clay) nature.
  • Porosity and texture provide good drainage and other conditions favorable for agriculture.
Chemical Characteristics
  • The proportion of nitrogen is generally low.
  • The proportion of potash, phosphoric acid, and alkalis is adequate.
  • The proportion of iron oxide and lime varies within a wide range.
Crops They yield splendid crops of rice, wheat, sugarcane, tobacco, cotton, jute, maize, oilseeds, vegetables, and fruits.
Rainfall
  • Above 100 cm – Suitable for paddy.
  • Between 50-100 cm – Suitable for wheat, sugarcane, tobacco, and cotton.
  • Below 50 cm – Coarse grains (millets).
BLACK SOILS
Distribution Maharashtra, Madhya Pradesh, parts of Karnataka, Telangana, Andhra Pradesh, Gujarat, and Tamil Nadu.
Formation Formed due to weathering of basaltic rocks which emerged during the fissure eruption of the Cretaceous period.
Share Spread over 46 lakh sq km (16.6% of the total area).
Physical Characteristics
  • The black color is due to the presence of a small proportion of titaniferous magnetite or iron and black constituents of parent rock.
  • The black soil is highly retentive of moisture. It swells significantly when accumulating moisture.
  • In summer, the moisture evaporates, and the soil shrinks, forming broad and deep cracks.
  • When dry, it develops cracks and has a blocky structure (Self Ploughing Capacity).
Chemical Characteristics
  • Contains 10% alumina.
  • Contains 9-10% iron oxide.
  • Contains 6-8% lime and magnesium carbonates.
  • Potash is variable (less than 0.5%), while phosphates, nitrogen, and humus are low.
Crops
  • Best suited for cotton crops.
  • Also supports wheat, jowar, linseed, Virginia tobacco, castor, sunflower, and millets.
  • Large varieties of vegetables and fruits can also be grown successfully on black soils.
RED SOILS
Distribution Found in regions such as Tamil Nadu, Madhya Pradesh, Jharkhand, Odisha, some parts of Karnataka, and southeast Maharashtra.
Formation Formed as a result of weathering of metamorphic and igneous rocks.
Share Covers 18.5% of the area.
Physical Characteristics
  • Rich in iron and potash but deficient in other minerals.
  • Texture: Sandy to clay and loamy.
  • Mostly loamy and cannot retain water as well as black soils.
  • Rainfall is highly variable, leading to three subtypes:
    • Red & Yellow Soil: Rainfall ~200 cm, found in NE India (Nagaland, Mizoram, Manipur Hills, parts of the Malabar coast), requires quick drainage.
    • Red Sandy Soil: Found in drier plateaus like Karnataka, Tamil Nadu, Telangana, Rayalaseema, with rainfall from 40-60 cm.
    • Red Alluvial Soil: Found along river valleys, known for good fertility.
Chemical Characteristics Deficient in phosphate, lime, magnesia, humus, and nitrogen.
Crops
  • Supports rice, sugarcane, and cotton cultivation.
  • Millets and pulses are grown in drier areas.
  • Large regions of Karnataka and Kerala have developed Red soil regions for rubber and coffee plantation farming. 
LATERITE SOILS
Distribution
  • Found in patches in the Western Ghats (Goa and Maharashtra).
  • Belgaum district of Karnataka and in the laterite plateau of Kerala.
  • In the state of Orissa, in the Eastern Ghats.
  • Amarkantak plateau region of Madhya Pradesh.
  • Panchmahal district of Gujarat.
  • Santhal Pargana divisions of Jharkhand.
Formation
  • Formed under conditions of high temperature and heavy rainfall with alternate wet and dry periods.
  • Heavy rainfall promotes leaching (nutrients get washed away by water), causing lime and silica to be leached away and leaving behind soil rich in oxides of iron and aluminum compounds.
Share Widespread in India, covering over 10% of the total geographical area.
Physical Characteristics
  • Moderate humus and water-retaining capacities.
  • Red in color due to little clay and more gravel or red sand-stones.
Chemical Characteristics
  • Rich in bauxite or ferric oxides.
  • Very poor in lime, magnesia, potash, and nitrogen.
  • Sometimes, phosphate content may be high in the form of iron phosphate.
Crops
  • Suitable for crops like groundnut, cashew nut, etc.
  • Laterite soil in Karnataka supports coffee, rubber, and spices farming.
MOUNTAIN/FOREST SOIL
Distribution Mainly found in the Himalayan region, Sikkim, Arunachal Pradesh, Assam, and also in Peninsular India and the Eastern Ghats.
Formation Governed by the deposition of organic matter derived from forests, with characteristics that change according to parent rocks, ground configuration, and climate.
Share Occupies about 2.85 lakh sq km (8.67% of the total land area of India).
Physical Characteristics
  • Rich in organic content—adequate humus, but other nutrients are deficient.
  • Loamy soil formed when sand, silt, and clay are mixed.
Chemical Characteristics
  • Deficient in potash, phosphorus, and lime.
  • Very rich in humus.
Crops
  • Maize, barley, wheat, and temperate fruits are grown in this soil in the Himalayan region.
  • Plantation of crops like tropical fruits, coffee, tea, or spices in the southern states of India such as Kerala.
DESERT/ARID SOIL
Distribution Occurs in arid and semi-arid regions of Rajasthan, Punjab, and Haryana.
Formation Desert soils form in areas where the demand for water by the atmosphere (evaporation) and plants (transpiration) is much greater than precipitation.
Share Covers an area of 1.42 lakh sq km (or 4.32% of the total area).
Physical Characteristics
  • Sandy with low organic matter.
  • Living microorganisms are low in content.
Chemical Characteristics
  • Lacks moisture content; humus content is low, and nitrogen is initially low but can be available in the form of nitrates.
  • Rich in iron content.
  • Phosphorus content is nearly adequate and rich in lime and bases.
  • Calcium content increases downward, with the subsoil containing ten times more calcium.
Crops Only drought-resistant and salt-tolerant crops such as barley, cotton, millets, maize, and pulses are grown.
PEATY SOILS
Distribution
  • Found in Kottayam and Alappuzha districts of Kerala where it is called “Kari.”
  • Also occurs in the coastal areas of Odisha and Tamil Nadu, the Sundarbans of West Bengal, Bihar, and Almora district of Uttarakhand.
Formation Formed from partially decomposed plant material under anaerobic water-saturated conditions.
Physical Characteristics
  • Dominated by clay and mud, making it heavy.
  • Rich in moisture content but with a high salt content; daily inundation by high tide makes it infertile.
  • Organic matter in these soils may go up to 40-50%.
Chemical Characteristics
  • Black, heavy, and highly acidic.
  • Deficient in potash and phosphate.
SALINE AND ALKALINE SOILS
Distribution Found mainly in the states of Gujarat, Bihar, Haryana, Rajasthan, Maharashtra, Odisha, Andhra Pradesh, Kerala, Tamil Nadu, Uttar Pradesh, and West Bengal.
Formation
  • Formed due to dried-up lakes or due to faulty farming practices.
  • The cause of soil salinity and modification is multifactorial, and any process that affects the soil-water balance may impact the movement and accumulation of salts in the soil.
Share Around 6.727 million hectares in India, approximately 2.1% of the geographical area of the country, is salt-affected.
Physical Characteristics In regions with high sub-soil water tables, injurious salts are transferred from below by capillary action, resulting from evaporation in the dry season.
Chemical Characteristics
  • These soils constitute about 10-40% of the organic matter and contain a reasonable amount of soluble salts.
  • Undecomposed rock fragments, on weathering, release sodium, magnesium, calcium salts, and sulphurous acid.
Crops The soil is infertile.

 

Issues with Indian Soil

  • Soil Erosion: Caused by natural factors like wind erosion and human activities such as excessive farm runoff and overgrazing, leading to the loss of topsoil and making it infertile.
  • Deforestation: Facilitates the loss of the topsoil due to surface runoff as tree roots, which bind the soil and keep it intact, are removed.
  • Faulty Agriculture: Practices involving high fertilizer use and monocropping damage the soil, making it infertile.
  • Soil Salinity: Multifactorial causes; any process affecting the soil-water balance can influence salt movement and accumulation.
  • Mining Activities: Coal mining causes drastic changes in the soil profile and reduces soil organic carbon and nutrient pools.
  • Sea Level Rise: Low-lying coastal areas are inundated with saltwater, contaminating the soil.
  • Nutrient Imbalance: Essential for high crop yields, but excessive or imbalanced nutrient inputs can pose risks to the environment, human health, and ecosystems.
  • Soil Contamination: Both natural (geogenic) and human-made (anthropogenic) factors contribute to soil and water pollution.
  • Soil Sealing: Urban expansion takes over fertile soils, reducing the availability of productive land and extending urbanization beyond traditional city limits.

 

Socio-Economic Impact of Soil Infertility

  • Food Security: Soil fertility is essential for sustaining agriculture; without it, crops fail, and land becomes barren.
  • Poverty: Loss of soil fertility could push landowners and those dependent on cultivation into poverty.
  • Deforestation: Increased soil infertility leads to forest clearing for new farmland, which destroys biodiversity in the area.
  • Migration: People may migrate from rural farm areas to urban areas due to decreased agricultural productivity.
  • Crop Failure: Soil infertility can lead to crop failure and drought-like conditions in agricultural areas.

 

Way Forward and Soil Conservation

  • Crop Rotation: Conserves soil fertility by allowing different crops that require different nutrients to be rotated, giving the soil time to restore lost nutrients.
  • Reduce Jhum: Reducing shifting cultivation by persuading tribal people to adopt settled agriculture is an effective method for soil conservation.
  • Contour Bunding: Terracing and contour bunding divide hill slopes into smaller areas, slow down water flow, promote water absorption, and help prevent soil erosion.
  • Afforestation: Maintaining 20-25% forest cover is considered healthy for soil and water conservation.
  • Organic Practices: Reducing the use of inorganic fertilizers preserves soil fertility.
  • Terrace Planting: Utilizes the natural topography to benefit from the way rainwater flows, helping to prevent erosion.
  • Native Cropping: Planting native crops that enhance the soil helps to sustain conservation efforts.

 

SOILS IN INDIA

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