• Soil is like a mix of stuff—plants, rocks, air, water, and tiny living things. It's what helps plants grow and supports life.

Introduction

• Soil is made up of two parts: solid stuff like minerals and plants, and a sponge-like part that holds air and water. It forms when rocks break down due to things like wind and water, a process called weathering. The type of soil depends on the rocks and plants in the area.
• Soil has different layers with various textures, colors, and chemicals. Each layer, called a horizon, is not the same thickness. When you see a cutout of soil layers, it's called a soil profile.
• The process of soil development is called Pedogenesis. Factors like the type of rocks, landscape, weather, plants, and time play a role in forming soil. Pedology is the science that studies everything about soils, from their physical and chemical traits to how living things contribute to soil, and even how soils are created and change over time.

Process of Soil Formation

Soil formation starts with a parent material, like rocks, that decides what minerals are in the soil. There are five main ways soil is made:

• Lateralization: Happens in warm places and changes rocks into clay and laterite.
• Calcification: This occurs when water evaporates more than it rains, bringing up salts from the ground, usually calcium carbonate.
• Podsolization: In cold and damp areas, iron and aluminum mix with silica and organic stuff, leaving the soil.
• Gleying: When the ground is always wet and doesn't drain well, organic stuff builds up on top, and iron turns the lower layers blue-grey.
• Salinization: Like calcification but with salt. Happens in dry areas or when there's too much irrigation water.

Factors for Soil Formation

Factors that affect how soil forms include the starting material, the climate (hot, cold, wet, dry), the shape of the land, living things like plants and animals, and the time it takes for soil to develop.

• Parent Material: Soil comes from rocks. The kind of rock decides what the soil is like—its color, feel, and minerals.
• Climate: Weather is a big deal in making soil. Rain and heat make rocks break down faster. In warm places with rain, there are more plants and more soil gets carried away. In cold areas like the Himalayas, plants decay very slowly. 
• Organic Content: This is the dead plants and animals in the soil. It helps soil erosion and breaks down nutrients. It also affects how fast humus forms.
• Topography: The shape of the land matters too. Flat places usually get more soil, like the Indo-Gangetic plain, while steep areas lose soil easily.
• Time: Time is the last thing. It decides how thick the soil is and how old it is. Older soil had more time to form, depending on the other things mentioned.

Major Soils of India

The Indian Council of Agricultural Research (ICAR) grouped Indian soils based on their nature and character, following the United States Department of Agriculture (USDA) soil classification.

Alluvial Soils

• These soils cover more than 40% of India's land and form when sediments like sand, silt, and clay settle in layers. There are two types: newer alluvium (Khadar) and older alluvium (Bhangar). Bhangar lands are usually above flood levels and have Bhurs (wind deposits) and Usar soils.
• Khadar, or newer alluvium, is deposited by yearly floods, adding fine silt to the soil. Alluvial soils are great for growing crops like rice, wheat, oilseeds, sugarcane, jute, pulses, maize, millets, and fodder. They're mainly found in Northern plains, river valleys, and coastal areas.

Red Soils

• These soils form on old crystalline and metamorphic rocks, covering more than 18% of India's land. They get their red color from high iron content and turn yellow when hydrated. Because of the sandy texture, they don't hold much water.
• These soils are found in hot and humid regions, especially in states like Tamil Nadu, Karnataka, Andhra Pradesh, Telangana, Chhattisgarh, Jharkhand, Madhya Pradesh, and Odisha. They lack phosphorus, nitrogen, and lime but have a good amount of potash. The main crops grown in red soils include rice, maize, millet, pulses, and small grains.

Black or Regur Soils

• These soils make up around 15% of India's land and are often called black cotton soils or regur. They come from weathered lava rocks and are found in Maharashtra, parts of Andhra Pradesh, the Northern Plateau, parts of Karnataka, Western parts of Madhya Pradesh, and Southeastern parts of Gujarat.
• Black cotton soil forms from the weathering of igneous rocks and lava cooling after a volcano eruption. These soils are mature, with a high capacity to retain water. They're rich in iron, lime, calcium, potash, magnesium, and aluminum. The soil is generally clayey, deep, and doesn't let water pass through easily. When wet, it's tough and sticky, forming wide cracks when dry.
• These soils are mainly used for growing crops like cotton, millet, maize, pulses, and citrus fruits such as oranges and lemons. Plowing can be challenging when the soil is wet because the plow gets stuck in the mud.

Arid and Desert Soils

• These soils have a sandy texture and are rich in mineral salts but lack organic matter. They have a high pH value. Found in regions like the Rajasthan desert, parts of Gujarat, Southwest Haryana, and Southwest Punjab, where the yearly rainfall is less than 40 cm, these soils cover an area of 1.42 lakh sq km. They are reddish-brown in color, and the sandy parts are called "bhur."
• These soils are not great in nitrogen and organic material. With proper irrigation development, they can be improved. Generally, these soils are used for growing crops like bajra, pulses (green-gram, black-gram), guar, fodder, millets, and jowar.

Mountain Soils

• These soils are in the hills of the Himalayas, in the dry parts of the Peninsula, and in some areas of the Andaman and Nicobar Islands.
• There are two types of mountain soil: Podzol soil and Prematured and Bouldered soil. 
• The terai soils in the foothills of the Himalayas are rich in nitrogen and organic matter. In the coniferous forest belt of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and Sikkim, brown Podzol soils are found. Mountain soils with good vegetation cover have lots of organic matter, but their nutrient levels vary based on how much nutrients are washed away.
• These soils lack potash, phosphorus, and lime, and are not very fertile. They are suitable for growing tea, coffee, spices, and tropical fruits in some areas, and for cultivating wheat, maize, and barley in Northern regions.

Forest Belt of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and Sikkim:

• Brown Podzol soils predominate in this region.
• Mountain soils are enriched with organic matter, but their base status varies due to leaching.
• Deficient in potash, phosphorus, and lime, with low fertility.
• Suitable for tea, coffee, spices, tropical fruits in Southern regions, and wheat, maize, and barley in Northern regions.

Laterite or Lateritic Soils:

• Derived from the Latin word "later," meaning brick.
• Covers about 3.7% of the country's total area.
• Typical of monsoon and humid tropical zones with a deep weathered layer.
• Rich in iron and aluminum, but poor in humus, phosphorus, potassium, lime, and nitrogen.
• Reddish color due to iron and aluminum residue; prone to erosion and degradation.
• Found in Odisha, West Bengal, parts of Andhra Pradesh, Tamil Nadu, Kerala, Jharkhand, Chhattisgarh, Maharashtra, and Madhya Pradesh.

Soil Moisture Map:

• Developed by IIT Gandhinagar and the India Meteorological Department (IMD) in October 2018.
• Uses a land surface model considering soil, vegetation, land use, and land cover.
• Available on the IMD website as Experimental Forecasts Land Surface Products.

Saline and Alkaline Soils:

• Contain high salt content; referred to as alkaline soils known by various names such as Thur, Kari, Chopan, reh, kallar, and usar.
• Sandy to loamy sand texture with a pH value of 8.5.
• The tracts of Punjab, Rajasthan, and Maharashtra exhibit the presence of Choi, Biat, and Ound soil types. Bihar, Uttar Pradesh, and Haryana also share these soil types.
• These soils contain undecomposed rock and mineral elements, releasing sodium, magnesium, calcium salts, and sulfur. They range in texture from sandy to loamy, and despite being deficient in nitrogen and calcium, they can be reclaimed through effective irrigation, gypsum application, and the cultivation of salt-resistant crops.
• Primarily used for cultivating rice, wheat, cotton, sugarcane, and tobacco, these soils in regions like Punjab and Haryana become saline due to intensive irrigation and dry climatic conditions.
•  Originating from the mechanical disintegration of ground rocks or blown from the Indus basin and the coast by the prevailing Southwest monsoon winds, these soils present unique characteristics.

Forest soils

• Forest soils, formed in forest areas with sufficient rainfall, vary in structure and texture based on the mountain environment where they develop. 
• Found in the lower valleys of the snow-bound areas of the Himalayas, these soils are fertile but acidic with low humus content.

Karewa soils

• Karewa soils, derived from lacustrine deposits in the Kashmir valley and Bhadarwah valley of Jammu, mainly consist of fine silt, clay, sand, and boulder gravel.
•  Ideal for cultivating saffron, almond, walnut, apricot, apple, and peach orchards, Karewas in places like Palampur, Pulwama, and Kulgam are renowned for producing high-quality saffron, walnut, and almond.

Peaty and marshy soils

• Peaty and marshy soils, originating in humid regions due to the accumulation of organic matter, are heavy, black, and highly acidic.
•  These soils, deficient in phosphate and potash, are suitable for jute and rice cultivation in Bengal and for growing spices and rubber near the Malabar coast.

Snowfields

• Snowfields found above the snow line in mountainous and glacial terrain, exist under the snow and glaciers at the highest peaks of the greater Himalayas, Karakoram, Ladakh, and Zanskar.

•  Immature and unsuitable for crops, this type of soil is characterized by its presence under permanent snow and ice accumulation.

Properties Of Major

Soil Erosion and Damage to Soil

Some problems related to soil are explained below.

Soil Erosion:

• Soil erosion is when the topsoil on land gets loosened and moved. Natural forces like water and wind are always causing soil erosion, which makes the soil less fertile.

• People doing harmful activities have made soil erosion happen even more.

Types of Soil Erosion:

There are different ways soil can erode:

• Wind Erosion: This happens where natural plants are gone, usually in dry areas near sandy shores of oceans, lakes, and rivers. The wind blows and carries loose soil particles.
• Water Erosion: Running water, like rain or waves, carries away soil particles. It can cause floods, be dangerous for people, and ruin agriculture.

The four types of water erosion are:

• Splash Erosion: Raindrops act like tiny bombs, hitting soil and breaking it. Plants help prevent this.
• Sheet Erosion: Rainwater flowing slowly takes away soil particles.
• Rill and Gully Erosion: Small rills appear on cultivated land after sheet erosion. When they get bigger, they're called gullies. Ravines are deep gullies.
• Ocean Waves (Coastal Erosion): Happens along seashores when waves erode the soil.

Causes of Soil Erosion:

Here are the reasons soil erodes:

• Deforestation: Cutting down trees removes the plants that hold soil in place. Some replacement plants, like coffee, cotton, palm oil, soybean, and wheat, can make erosion worse.
• Overgrazing: Too many animals eating plants don't let them recover. The soil gets crushed and carried away, especially in areas where recovery time is not given.
• Water Erosion: Rain or melting snow displaces soil on the ground. More water flow means more soil particles are moved away. Land without plants, like empty fields after harvesting crops, is at risk of water erosion.
• Wind Erosion: Wind erosion is when the wind naturally moves and deposits soil. It usually happens in dry, sandy places or where the soil is loose, dry, and finely granulated. This process harms both human-made structures and natural plants by taking soil from one place and dropping it somewhere else.

Soil Degradation:

• Soil degradation happens because of human actions, causing the quality and richness of the soil to decline. Worldwide, land is degrading quickly because of unsustainable human activities like improper crop rotation. 
• For example, in the Great Plains of India, soil fertility has significantly decreased. Planting leguminous crops can help improve soil fertility in affected areas.

Water Logging:

• Water logging is when the soil becomes too saturated with water, either temporarily or permanently. When there's too much water, the soil can't absorb it properly. This can occur when the water table rises, affecting the soil pores in the crop root zone. It reduces the normal supply of air in the soil, lowers oxygen levels, and increases carbon dioxide and ethylene levels. It has impacted land along the Indira Gandhi Canal in Rajasthan and nearby areas.

Desertification:

• Desertification is the deterioration of land in dry areas due to various factors, including extreme weather conditions like drought and human activities that pollute or degrade soils.
•  It negatively affects food production, livelihoods, and the overall health of ecosystems, even though it doesn't mean the expansion of existing deserts.

Soil Conservation:

• Soil conservation aims to prevent the top layer of soil from degrading due to erosion and exhaustion, ensuring a fertile and healthy environment. The Central Government established the Central Soil Conservation Board in 1953 to oversee soil conservation efforts.

Methods of Soil Conservation:

There are engineering and biological methods for soil conservation.

Engineering Methods:

• Contour Bunding: Making embankments to reduce water flow.
• Contour Barriers: Live or dead barriers that intercept water and soil flow.
• Sand Fences: Barriers made of wooden slats to prevent wind-blown sediments.
• Shelter Belts: Windbreaks in coastal and dry regions.
• Rock Dam: Slows water flow to prevent gully erosion.

Biological Methods:

• Crop Rotation: Planting different crops on the same land to improve soil health and nutrient optimization.
• Strip Cropping: Strip cropping involves growing crops alternately in a rotation system to make sure that the entire area is never left bare at any time of the year.
• Mulching: Mulching is adding a layer of organic matter to the soil, which helps it retain water better.
• Vermi Composting: Vermicomposting uses different types of worms to break down organic matter, making the soil more fertile.
• Afforestation: Afforestation is the process of planting trees in areas that haven't had tree cover for a while.

Social Methods:

Social methods of soil conservation include:

• Checking Overgrazing: Overgrazing harms plant communities, so it's important to manage animals properly to prevent overgrazing. This can be done through methods like rotational, cell, and mob grazing.
• Banning Jhum (Shifting Cultivation): Jhum is a farming practice where vegetation is cleared and burned, leading to a loss of soil fertility. Banning this practice helps protect the soil.

International Year of Soil:

• In 2002, the International Union of Soil Science (IUSS) decided to dedicate December 5th every year as World Soil Day to highlight the importance of healthy soil and promote sustainable soil management. 
• The Food and Agriculture Organization (FAO) initiated World Soil Day and it was unanimously approved at the FAO Conference in 2013. 
• The United Nations adopted World Soil Day in its 68th General Assembly in December 2013, declaring it to be observed on December 5th annually. Since 2012, FAO has been celebrating World Soil Day.

Prelims Facts

• In India, the maximum area is covered by which type of soil

- Alluvial soil [WBCS (Pre) 2017, CGPSC (Pre) 2017)

• The Characteristic feature of Bhur of Upper Ganga Plain of India is

- Undulating, aeolian sandy deposit [WBCS (Pre) 2014]

• In which soil the Phosphoric Acid is found in rich quantity?

- Alluvial soil [CGPSC (Pre) 2021]

• Which type of soil has minimum water retention capacity?

- Alluvial sand soil [UKPSC (Pre) 2003]

•  The soil particles which are present in loamy soil, are

- Sand particles, clay particles, and silt particles [BPSC (Pre) 2011]

• Which soil is predominantly found in the districts of Muzaffarpur, Darbhanga, and Champaran

- Newer Alluvium [BPSC (Pre) 2017]

•  The black cotton soil of India has been formed due to the weathering of

- Fissure Volcanic Rock [IAS (Pre) 2021]

•  Which soil of India has been formed due to weathering of Basaltic Lavas?

- Regur Soil [UPPSC (Pre) 2015]

• Regur soil of India has been most widespread

- Maharashtra [BPSC (Pre) 2000]

•  Regur soil of the Deccan trap are black in colour because

- It is formed out of weathering of Basaltic Lava [UPPSC (Pre) 2013]

•  Lava soil also known as 'Black soil' in India are found in

- Malwa Plateau [UPPSC (Pre) 2010]

•  Which Soil found in Deccan Plateau has higher fertility, poor drainage and is prove to salinity and sodicity?

- Deep black soil [MPSC (Pre) 2020]

• Gangani region of West Bengal has which type of soil

- Laterite soil [WBCS (Pre) 2020]

•  Which soil types of India is rendered infertile by the presence of excess iron

- Laterite [LAS (Pre) 1994]

•  Laterite Soil develops in which areas

- Areas with high temperature and heavy rainfall [JPSC (Pre) 2021)

• In which type of the rocks have red and yellow soils of Chhattisgarh developed?

- Granite Schist [CGPSC (Pre) 2021)

•  What is the reason for the red soil having the colour red?

- Presence of Ferric Oxides (UPPSC (Pre) 2010.

Self Check

1. A fertile soil, suitable for growing common crops is likely to have a pH value of

IAS (Pre) 1993

(a) 3

(b) 4

(c) 6 to 7

(d) 9 to 10

2. Which one of the following soils is deposited by rivers?

BPSC (Pre) 2017

(a) Red soil

(b) Black soil

(c) Alluvial soil

(d) Laterite soil

3. Choose the correct statement out of the four statements given regarding alluvial soil.

CGPSC (Pre) 2021

(a) This soil is found in about 14% portion of India's land surface.

(b) Phosphoric acid is found in rich quantities in this soil.

(c) This soil is also known by names such as Reh, Thur, Chopan.

(d) This soil is not fertile.

4. Which soil is predominantly found in the districts of Muzaffarpur, Darbhanga and Champaran?

BPSC (Pre) 2017

(a) Black soil

(b) Newer alluvium

(c) Older alluvium

(d) Red soil

5. On which type of the following rocks have red and yellow soils of Chhattisgarh developed?

CGPSC (Pre) 2021

(a) Granite Schist

(b) Basalt

(c) Sandstone

(d) Limestone

6. In our country, the second largest area is occupied by

Odisha PSC (Pre) 2015

(a) alluvial soil

(b) red soil

(c) black soil

(d) laterite soil

7. Observe the statements regarding soils in Maharashtra.

MPSC (Pre) 2020

1. Regur soil contains aluminium and iron at a sufficient level.
2. Laterite soil is found in moist climates.
3. Red soil is found in Bhandara district.
4. Red soil contains less amount of organic matter.

Codes

(a) Only statement 1 is correct.

b) Statements 1, 2 and 3 are correct.

(c) Statements 1, 3 and 4 are not correct.

(d) All of the above

8. The black cotton soil of India has been formed due to the weathering of

IAS (Pre) 2021

(a) brown forest soil

(b) fissure volcanic rock

(c) granite and schist

(d) shale and limestone

9. Which of the following soils of India is most suitable for cotton cultivation?

MPPSC (Pre) 2004, UPPSC (Mains) 2014

(a) Regur soil

(b) Laterite soil

(c) Alluvial soil

(d) Red soil

10. Among the local names of soils found in Chhattisgarh, which one is not correct?

CGPSC (Pre) 2021

(a) Yellow clay soil                          Matasi

b) Black soil                                     Kanhar

c) Mixture of black and yellow soil   Kachhar

(d) Infertile laterite soil                         Bhata

11. In which region of Madhya Pradesh, the black soils are not found?

MPSC (Pre) 2022

(a) Malwa plateau

(b) Narmada valley

(c) Baghelkhand

(d) Satpura range

12. Gangani region of West Bengal has which type of soil?

WBCS (Pre) 2020

(a) Alluvial soil

(b) Saline soil

(c) Laterite soil

(d) Terai soil

13. Which of the following statements is true regarding laterite soil in India?

JPSC (Pre) 2021

1. Laterite soil develops in areas with high temperatures and heavy rainfall.
2. Laterite soil is rich in humus and found in West Bengal, Assam, and Odisha.

Codes

(a) Both 1 and 2

(b) Neither 1 nor 2

(c) Only 1

(d) Only 2

14. In India, the maximum alkali area is found in the state of

UPPSC (Mains) 2007

(a) Gujarat

(b) Haryana

(c) Punjab

(d) Uttar Pradesh

15. Following are the statements regarding the USAR soil.

1. It is reclaimed by adding lime.
2. This soil has pH more than seven.
3. Paddy crop can be grown in this soil.

Codes

(a) 1 and 2 

(b) 2 and 3 

(c) Only 3 

(d) Only 1

16. Assertion (A) The percentage of net sown area in the total area of Andhra Pradesh is less as compared to that of West Bengal.

Reason (R) The soil of most of Andhra Pradesh is laterite

AS (Pre) 2006

Codes

(a) Both A and R are true and R is the correct explanation.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true.

17. Assertion (A) The Himalayan soils are rich in humus.

Reason (R) The Himalayas have the largest area

under forest cover.

Codes

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true, but R is not the correct explanation of A.

(c) A is true, but R is false.

(d) A is false, but R is true.

18. Karewas soils, which are useful for the cultivation of Zafran (a local variety of saffron) are found in BPSC (Pre) 2018

(a) Kashmir Himalaya

(b) Garhwal Himalaya

(c) Nepal Himalaya

(d) Eastern Himalaya

19. Which of the following statements is not true about Matasi soil?

CGPSC (Pre) 2022

(a) This soil is usually found at altitudes higher than tha of Bhata soil and lower than that of Kanhar soil.

(b) This soil is less fertile than Kanhar soil.

(c) Iron content is high in this soil.

(d) Sand content is high in this soil.

20. In which one of the following areas in India, the problem of soil erosion is critical?

UPPSC (Pre) 2004, MPPSC (Pre) 2006

(a) Malwa plateau

(b) Foothill areas of Shivalik ranges

(c) Dandakaranya

(d) Meghalaya plateau

Know Right Answer

1 (c)

2 (c)

3 (b)

4 (b)

5 (a)

6 (c)

7 (d)

8 (b)

9 (a)

10 (c)

11 (c)

12 (c)

13 (c)

14 (d)

15 (a)

16 (c)

17 (a)

18 (a)

19 (a)

20 (b)