Soil types, formation and its characteristics

Published on 02 Feb 2025

Soil is a complex mixture of minerals, organic matter, water, and air that supports plant life. There are many different types of soil, each with its own unique characteristics. Some of the most common soil types include:

Types of soil

• Alluvial soil: Formed from the deposits of rivers and streams. It is typically fertile, well-drained and found in river valleys.

• Example: Gangetic plains alluvial soil formed by Ganga River.

• Black Soil (Regur): This type of soil is formed from the weathering of basalt rock. It is dark in colour and has a high clay content.  Also known as black cotton soil, it is rich in minerals like calcium and magnesium.

• Example: Black soil of Deccan plateau.

• Red soil: It is typically red or orange in colour and has a low clay content. Red soil is not as fertile as alluvial or black soil, but it is still suitable for growing some crops.

• Example: Eastern Ghats, parts of Tamil Nadu, Karnataka, and Andhra Pradesh in India.

• Laterite Soil: Found in areas with high temperatures and heavy rainfall. It is leached of its nutrients and tends to be infertile.

• Example: Western Ghats in India, parts of Kerala, Karnataka, Goa, and Maharashtra.

• Arid and desert soil: Found in arid regions, it lacks organic matter and is saline. It is typically sandy and has a low water content.

• Example: Thar Desert in north-western India, parts of Rajasthan and Gujarat.

• Mountain soil:  This type of soil is formed in mountainous areas. It is typically shallow and rocky. Mountain soil is not as fertile as other types of soil, but it is still suitable for growing some crops.

• Example: Himalayan region, including states like Himachal Pradesh, Uttarakhand, and parts of Jammu and Kashmir.

• Peat soil: Composed of partially decayed organic matter, found in waterlogged and marshy areas. It is typically black or dark brown in colour and has a high organic content.

• Example: Kerala Backwaters in India, Sundarbans Delta in West Bengal.

• Forest soil: This type of soil is formed under forest cover. It is typically rich in organic matter and is well-drained. Forest soil is fertile and is suitable for growing a variety of crops.

• Example: soil in North East India 

Factors influencing formation of soil

Soil formation, also known as pedogenesis is a complex process that takes place over many years. The five main factors that influence soil formation are:

• Parent material: Different rocks weather at different rates, influencing the mineral composition of the soil. It also depends upon the depth of weathering mantle.

• Example: Granite, a common igneous rock, weathers to form soils with high mineral content, often seen in mountainous regions.

• Climate: Weathering processes are more active in warm and humid climates, leading to faster breakdown of rocks and organic matter. Arid climates may result in the accumulation of salts.

• Example: Tropical rainforests experience high temperatures and heavy rainfall, leading to intense weathering and the formation of laterite soils.

• Topography: Sloping areas may experience erosion, while flat areas may accumulate water and develop poorly drained soils.

• Example: Sloping areas in the Himalayan region may experience erosion, leading to the development of colluvial soils at the base of slopes.

• Biological activity: The activity of soil organisms, influences soil structure and nutrient cycling. These organisms contribute to the breakdown of organic matter and the development of soil structure.

• Example: warm area have lower humus content due to high microbial activity.

• Time: Soil formation is a time-dependent process. The longer a soil-forming process operates, the more developed the soil profile becomes. Soils in older landscapes tend to be more mature and well-developed.

• Example: The soils in ancient landscapes, like those in the Amazon Basin, have undergone extensive weathering and development over millions of years.

Process of soil formation

• Weathering: Breakdown of rocks into smaller particles due to physical, chemical, or biological processes.

• Leaching: The removal of minerals and nutrients from the soil by water percolating through it.

• Illuviation: The downward movement and deposition of soil material.

• Eluviation: The downward movement of soil material, removing it from a particular horizon.

• Organic Matter Decomposition: The breakdown of plant and animal remains, contributing to soil fertility.

• Horizon Development: The layering of soil into distinct horizons (O, A, B, C) based on different characteristics.

Soil characteristics 

• Texture: Refers to the proportion of sand, silt, and clay particles. It influences water retention, drainage, and aeration.

• Example: Sandy soils have a coarse texture and poor water retention, often found in arid regions like the Sahara Desert.

• Structure: The arrangement of soil particles into aggregates. It affects water movement and root penetration.

• Example: Granular soil structure, characterized by well-aggregated particles, is common in well-drained grassland soils.

• Colour: Indicates the presence of different minerals and organic matter. Dark soils are often rich in organic content.

• Example: Red and yellow soil with the presence of iron content. 

• pH Level: A measure of soil acidity or alkalinity. It influences nutrient availability to plants.

• Example: laterite soils of Kerala are acidic in nature.

• Cation Exchange Capacity (CEC): The soil's ability to hold and exchange cations (positively charged ions) important for plant nutrition.

• Organic matter content: The amount of plant and animal matter in the soil.

• Example: Forest soils of North Eastern India having high organic matter content. 

Spatial distribution of soils in India 

• Alluvial soil: Accounts for 40% of soil in India. Found in the Indo-Gangetic plains, along major river valleys such as the Ganges, Brahmaputra, and Yamuna.

• Black soil: Predominantly in the Deccan Plateau, covering states like Maharashtra, Madhya Pradesh, and parts of Gujarat, Karnataka, and Andhra Pradesh.

• Red soils: Mainly in the eastern and southern parts of the Deccan Plateau, including parts of Tamil Nadu, Karnataka, Andhra Pradesh, and Maharashtra.

• Laterite soil: Western Ghats, parts of Kerala, Karnataka, Goa, and Maharashtra.

• Arid and desert soils:  Thar Desert in north-western India, parts of Rajasthan and Gujarat.

• Mountain or forest soils: Himalayan region, including states like Himachal Pradesh, Uttarakhand, and parts of Jammu and Kashmir.

• Peat soil: Found in waterlogged areas, such as the Kerala Backwaters and parts of the Sundarbans Delta.

• Other soils: Various other soil types, including saline and alkaline soils, can be found in coastal regions, arid areas, and parts of central India.

Tags:
Geography

Keywords:
Soil types formation and its characteristics of soil soil in India Types of soil Factors influencing formation of soil Process of soil formation Soil characteristics Spatial distribution of soils in India

Syllabus:
General Studies Paper 1

Topics:
Salient Features of Indian Geography