Types of Soil

Soil is one of the significant natural resources, like air and water. It is the topmost layer of the earth’s crust and is a mixture of finely powdered rocks, organic matter, liquids, myriad organisms, and other minerals. It acts as an interface between the hydrosphere, lithosphere, earth’s atmosphere, and biosphere. The proportion of critical ingredients determines the type of soil. But, factors such as vegetation, climatic conditions, and human activities, e.g., grazing, farming, or gardening also influence the soil formation process.

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Table of content

• What is Soil?
• Importance of Soil
• Layers of Soil
• Types of Soil in India
• Classification of Soil type
• Conclusion
• FAQs

What is Soil?

• Soil is the loose surface material that covers most land.
• It consists of inorganic particles and organic matter.
• It provides the structural support to plants used in agriculture and is also their source of water and nutrients.
• It varies greatly in their chemical and physical properties.
• Processes such as leaching, weathering and microbial activity combine to make a whole range of different soil types.
• Each type has particular strengths and weaknesses for agricultural production.

Importance of Soil

• Soils serve as media for growth of all kinds of plants.
• It modifies the atmosphere by emitting and absorbing gases (carbon dioxide, methane, water vapor, and the like) and dust.
• It provides habitat for animals that live in the soil (such as groundhogs and mice) to organisms (such as bacteria and fungi), that account for most of the living things on Earth.
• Soils absorb, hold, release, alter, and purify most of the water in terrestrial systems.
• Soils process recycled nutrients, including carbon, so that living things can use them over and over again.
• Soils serve as engineering media for construction of foundations, roadbeds, dams and buildings, and preserve or destroy artifacts of human endeavors.
• Soils act as a living filter to clean water before it moves into an aquifer.

Layers of Soil

• Soil layers are called horizons. Most soil types have three or four different horizons.
• Based on their characteristics, soils horizons are named using different letters.

O horizon:

• It covers the surface of the ground.
• It’s mainly composed of organic matter like decomposing leaves or bugs.
• This organic matter is called humus.
• Depending on the location, the O horizon can be very thick or entirely missing.

A horizon:

• Often called topsoil, the A horizon consists of surface soil.
• This layer mainly contains minerals and decomposed organic material.
• Most plant roots grow in the A horizon.

E horizon:

• It is also known as the eluviated layer.
• Clay, minerals, and organic matter leach down out of this layer.
• Sand and silt particles of quartz are left behind.
• It is often found in older soils and forest soils.

B horizon:

• It consists of subsoil, which lies beneath the surface soil.
• This layer has clay and mineral deposits.
• It has less organic material than the O and A horizon.

C horizon:

• It is also called the substratum.
• The C horizon contains very little organic material.
•  It mainly consists of rock fragments. This rock is called parent material because soil develops from it.
• Plant roots do not grow in this layer.

R horizon

• It is also called bedrock.
• It consists of large areas of solid rock, including granite, limestone and sandstone.

Types of Soil in India

• In India various types of soils are found, and their formations are affected by certain factors such as altitude, climate, disproportionate rainfall, and many others.
• These soils are formed by the sediments brought down by the rivers.
• They also have varied chemical properties.

Classification of Soil type:

• Earlier, the soil was classified based on its fertility. The soil was either ‘Urvara,’ i.e., fertile or ‘Usara’ meaning non-fertile or sterile.
• In modern-day, various characteristics are taken into consideration, and the soil type is classified based on its texture, colour, moisture content, etc.
• In the year 1956, the Soil survey of India, an institution was established by the Government of India to study soil and its characteristics.

Major types of Soils found in India:

Laterite Soil:

• The term is derived from the word ‘Later’ which means ‘brick’.
• Laterite soil is found in those regions of the country which receive heavy rainfall with an alternate dry and wet period – mainly, near the coasts.
• This kind of soil becomes soft when wet and hardens when dry.
• In these climatic conditions, leaching of soil takes place, which is a process in which the fertile portion of the soil gets washed away by heavy rains.
• They are formed from the decomposition of rocks and contain iron oxide, which gives them red or pink color.
• This type of soil is ordinarily deficient in nitrogen and is weak in lime content; it is acidic soil.
• It is found in several parts of the country mainly Western and Eastern Ghats, Vindhyas, Malwa plateau, and Satpuras.
• The states where this type of soil can be found are West Bengal, Andhra Pradesh, Bihar, Meghalaya, Assam, and Odisha, to name a few.
• Laterite soil supports crops like Rice, Ragi, Sugarcane, rubber, coconut, tea, coffee and Cashew nuts.

Mountain Soils:

• Mountain soils are formed due to the accumulation of organic matter which is derived from the forest growth and is generally shallow, in-depth and immature.
• This type of soil is rich in humus but has poor lime, potash, and phosphorus content.
• It is usually sandy and has gravel.
• It is mainly found in the Himalayan region, Sikkim, Arunachal Pradesh, Assam, and also in Peninsular India, and the Eastern Ghats.

Characteristics of the mountain soil:

• Depending on the climate of the region, mountain soil can be divided into two broad groups: Loamy Podzols and High Altitude Soils.
• The mid-altitudinal zone in the Himalayas has Podzols.
• This soil is acidic with low humus and is found in Assam, Darjeeling, Kashmir, Uttaranchal, and Himachal Pradesh.
• 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 states of south India like Kerala, Tamil Nadu, and Karnataka are undertaken in this type of soil.
• In the drier areas or deciduous forest belt, deep soil, brown in colour and rich in humus is found.
• It is perfect for orchard crops.

Black Soil:

• This type of soil is made up of volcanic rocks and lava.
• Black soil is also known as ‘regur’ which is derived from the Telugu word ‘reguda’.
• Black soil is also known as Black Cotton Soil as cotton is an important crop that is grown in this type of soil.
• This soil is rich in calcium carbonate, potash, lime, and magnesium carbonate but has poor phosphorus content.
• It is mostly found in areas such as Gujarat, Madhya Pradesh, and Maharashtra.
• It is also found in states like Tamil Nadu, Andhra Pradesh, and Karnataka.
• Black soil is excellent and clayey and can hold a lot of moisture.
• It becomes sticky in the rainy season and develops cracks when dry.
• Black soil is good for producing cotton, oilseeds, wheat, linseed, millets, and tobacco.

Red Soil:

• This type of soil is formed as a result of weathering of metamorphic and igneous rocks.
• The red colour of the soil comes from the high percentage of iron content.
• Its texture varies from sandy to clayey, but it is mainly loamy.
• It is rich in potash content but lacks phosphate, hummus, and nitrogen content.
• The red soil is found in regions such as Tamil Nadu, Madhya Pradesh, Jharkhand, Odisha, some parts of Karnataka, and southeast Maharashtra.

Alluvial Soil:

• Alluvial soils are formed by the deposits of the sediments brought by rivers.
• Most of the rivers originate from the Himalayas and bring along a high amount of sediments with them.
• The soil is made up of particles like silt, sand, and clay.
• It has an adequate amount of phosphoric acid, potash, and lime.
• Alluvial soil is of two types –
• Old alluvium known as bangar
• New alluvium called khaddar.
• It is the most important type of soil found in the country as it covers about 40% of the total land.
• It is located in the northern plains beginning from Punjab to West Bengal and Assam.
• It is also found in deltas of different rivers such as Krishna, Godavari, Kaveri, and Mahanadi in peninsular India.
• Alluvial soil is highly fertile and is light grey in colour.
• Crops mainly cultivated include wheat, rice, maize, sugarcane, pulses, and oilseed.

Desert Soil:

• The desert soil is found in regions with low rainfall in an arid and semi-arid climate.
• The sand in the desert areas is partly original and partly blown from Indus Valley.
• The soil content has 90-95% of sand and 5-10% of clay.
• The phosphate content in the soil is high, while the nitrogen content is low.
• Desert soil lacks humus and moisture, and the water content in this soil is fulfilled through irrigation only.
• This type of soil is found in arid and semi-arid areas.
• Desert soil is found mostly in areas of Rajasthan extending to Rann of Kutch, and also in some areas of Haryana and Punjab.
• Cacti and shrubs are the permanent vegetation that can be seen in the deserts as it is very well adapted to living without moisture for long periods.
• Also, when it rains, the presence of phosphates and nitrates make desert soil fertile, and the desert blooms as dormant seeds wake up to life.

Saline and Alkaline Soil:

• There are many mineral-based and un–decomposed contents inside the earth.
• Due to weathering, they release certain minerals such as magnesium, sodium, sulfurous acid, and calcium salts.
• Some of the released spices get carried by rivers and mix in sub-soils of the plains making the soils saline and alkaline.
• Sometimes, these water-soluble salts move upwards with a rise in the water table during evaporation and transpiration.
• This type of soil can be found in Uttar Pradesh and Punjab and also in some parts of Gujarat.
• In the coastal areas, soil salinization occurs due to the accumulation of salts from inundated seawater.

Peat Soil:

• The accumulation of a high number of organic matter in the soil in humid regions results in the formation of peaty soils.
• These types of soils constitute about 10 to 40% of the organic matter and also a reasonable number of soluble salts.
• Peaty soils are heavy, black, and have high acidic content.
• They are low in phosphate and potash content.
• Peaty and marshy soils are found in a few districts of Kerala.
• On the other hand, marshy soils are found in coastal areas of some states such as Tamil Nadu, Bihar, Almora district of Uttaranchal, and Sundarbans of West Bengal.

Conclusion

Soil is the upper layer of earth in which plants grow, and it varies greatly in its composition and nature. Different types of soil are suitable for varying uses like agriculture, gardening, and construction. Each type of soil has unique properties that make it suitable for different uses, from agriculture to construction. Understanding these types and their characteristics can help in choosing the right soil for specific needs.

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