Major Types of Soil in India: Classification and Significance

Alluvial Soil

Alluvial soil is the most widespread and agriculturally important soil in India, covering about 15 lakh sq km or around 45-46% of the country. It is the base of India’s agricultural productivity and supports over 40% of the population.

1. Formation and Composition:
   Formed by sediments deposited by rivers originating from the Himalayas and coastal wave actions, alluvial soil is rich in potash, lime, and phosphoric acid but low in nitrogen. It is renewed regularly by floods, keeping it fertile.

2. Types:

1. Old alluvium (Bhangar) – clayey, darker, with lime nodules.

2. New alluvium (Khadar) – lighter, found on floodplains, more fertile.

3. Distribution: Mainly in the Indo-Gangetic plains (Punjab to West Bengal and Assam), valleys of Narmada and Tapti, east coast deltas, and northern Gujarat.

4. Characteristics: The soil varies from sandy loam to clay, light to ash grey in color, porous, and well-drained.

5. Crops: Supports rice, wheat, sugarcane, cotton, pulses, oilseeds, tobacco, and jute.

Black (Regur) Soil

Black Soil (Regur Soil) is primarily found on the Deccan Plateau, covering about 5.46 lakh square kilometers or approximately 16.6% of India’s total land area. It is famously known as "Black Cotton Soil" because it is ideal for the cultivation of cotton.

1. Formation and Composition: Black soil is formed from the weathering of volcanic rocks (trap rocks) and contains alumina, iron oxide, lime, magnesium carbonates, and potash. It is generally deficient in nitrogen, phosphorus, and organic matter.

2. Types and Characteristics: Black soil is highly argillaceous (clayey) with over 60% clay content, which allows it to retain moisture very well. It swells and becomes sticky during the rainy season and develops deep cracks in the dry season. This property helps in aeration and moisture retention, making it very fertile despite its nutrient deficiencies. The soil color ranges from deep black to grey.

3. Distribution: It is spread across Maharashtra, Madhya Pradesh, Gujarat, parts of Karnataka, Andhra Pradesh, and Tamil Nadu, mainly covering the Deccan Plateau and the Malwa Plateau.

4. Crops: Cotton is the principal crop grown, along with sugarcane, tobacco, millets (like jowar), wheat, oilseeds, pulses, citrus fruits, and sunflowers.

Red and Yellow Soil

Red and Yellow Soil covers about 3.5 lakh square kilometres or roughly 10.6% of India’s land area. These soils develop from the weathering of ancient crystalline and metamorphic rocks like granites and gneisses and owe their color to the presence of iron oxides.

1. Formation and Composition: Red soils are rich in iron and potassium but generally deficient in nitrogen, phosphorus, lime, and humus. The red color is due to iron oxide, turning yellow when hydrated. These soils have variable texture-from sandy to clayey-and are well-drained but often acidic.

2. Distribution: They are mostly found in Tamil Nadu, Karnataka, parts of Maharashtra, Andhra Pradesh, Madhya Pradesh, Chhattisgarh, Odisha, and some regions in Bihar, West Bengal, Rajasthan, and the northeastern states.

3. Characteristics: The soils are porous, well-drained, and sandy to loamy in texture. They tend to be poor in organic matter but can be fertile with proper fertilization and irrigation.

4. Crops: Suitable for cotton, wheat, rice, pulses, millets, tobacco, oilseeds, and potatoes. With proper management, they also support sugarcane and various fruits.

Laterite Soil

Laterite Soil covers about 2.5 lakh square kilometers in India and is mainly found in regions with high temperature and heavy rainfall, such as the Western Ghats, Eastern Ghats, parts of the Malwa Plateau, Rajmahal Hills, Vindhyas, and Satpuras.

1. Formation and Composition:
   Laterite soils are formed by intense leaching of the parent rock under tropical climatic conditions with alternate wet and dry periods. This process washes away silica and bases like lime and potash, leaving behind oxides of iron and aluminum, which give the soil its characteristic red color. It is poor in lime, magnesia, potash, and nitrogen but may sometimes have iron phosphate.

2. Characteristics: Laterite soil is coarse, porous, and acidic. It hardens when exposed to air, making it useful as building material. Due to leaching, it is generally low in fertility but can support plantation crops with proper manuring and irrigation.

3. Crops: Suitable for growing tea, coffee, rubber, coconut, cashew nuts, and arecanut especially in regions like Kerala, Karnataka, and Tamil Nadu.

Desert (Arid) Soil

Desert (Arid) Soil is found primarily in the arid and semi-arid regions of Rajasthan, parts of Punjab, Haryana, and Gujarat, covering about 1.42 lakh square kilometres or around 4.3% of India’s land area.

1. Formation and Composition: These soils consist mainly of aeolian (wind-blown) sand with 90 to 95% sand and 5 to 10% clay. They contain a high amount of soluble salts like calcium carbonate, making them alkaline. The soil is poor in organic matter and nitrogen but has relatively high phosphate content.

2. Characteristics: Desert soils have a sandy texture, low moisture retention, and poor fertility. The presence of kankar (calcium carbonate nodules) in lower horizons restricts water infiltration but helps retain moisture. The soil is often saline and alkaline due to high evaporation rates in dry climates.

3. Crops: Mainly drought-resistant and salt-tolerant crops like barley, millets, maize, pulses, and cotton survive here. Proper irrigation can improve soil fertility and crop yield.

Mountain (Forest) Soil

Mountain (Forest) Soil is found mainly in the hilly and mountainous regions of the Himalayas, Western Ghats, and Eastern Ghats, covering about 2.85 lakh square kilometers or around 8.6% of India’s land area.

1. Formation and Composition: These soils are formed by the decomposition of organic matter from dense forests along mountain slopes. They are rich in humus but generally deficient in potash, phosphorus, and lime. The soil texture varies with location-from loamy and silty in valley sides to coarse-grained on higher slopes.

2. Characteristics: Mountain soils are acidic, thin, and shallow, with poor horizon development. They are prone to erosion due to steep slopes and heavy rainfall but remain fertile where humus content is high.

3. Crops: They support plantation crops like tea, coffee, spices, and tropical fruits in the peninsular hills and wheat, maize, barley, and temperate fruits in the Himalayan region.

Saline and Alkaline Soil

Saline and Alkaline Soil occupy about 68,000 square kilometers in India and are mostly found in canal-irrigated areas and regions with a high water table. These soils are commonly present in parts of Andhra Pradesh, Telangana, Karnataka, Bihar, Uttar Pradesh, Haryana, Punjab, Rajasthan, and Maharashtra.

1. Formation and Composition:
   Saline soils have a high concentration of soluble salts like chlorides and sulphates, which affect plant growth due to osmotic stress. Alkaline (sodic) soils contain sodium carbonates and bicarbonates, making them alkaline with high pH. These soils commonly develop due to poor drainage, excessive irrigation, and salt deposition from sea tides in coastal areas.

2. Characteristics:
   These soils often have a white crust of salt on the surface and are infertile due to salt accumulation. They have poor soil structure, low permeability, and are hard when dry but dispersive when wet, causing issues in water retention and root penetration.

3. Crops:
   Salt-tolerant and drought-resistant crops like barley, cotton, millets, pulses, and maize are grown. Proper drainage and irrigation management can help reclaim these soils for cultivation.

Peaty and Marshy Soil

Peaty and Marshy Soil is found mainly in regions with high rainfall and humidity, covering an area of about 0.6 lakh square kilometers in India. These soils are common in the coastal regions of Kerala (Kottayam and Alappuzha), Odisha, Tamil Nadu, the Sunderbans in West Bengal, Bihar, and parts of Uttarakhand.

1. Formation and Composition: Peaty soils are formed due to the accumulation of a large amount of organic matter under waterlogged conditions where decomposition is incomplete. Marshy soils are similarly rich in organic content but are found in waterlogged or swampy areas. Both soils are rich in nitrogen but deficient in potash and phosphorus.

2. Characteristics: Peaty soils are heavy, spongy, and moisture-retentive, with a dark black color and high acidity. Marshy soils are also rich in organic matter and suited mainly for paddy cultivation. These soils require proper drainage for better agricultural use.

3. Crops: Suitable for paddy, and in some regions, crops like cabbage, carrots, and potatoes are grown.