The first scientific classification of soil was pioneered by Vasily Dokuchaev, a Russian soil scientist.
In India, the Indian Council of Agricultural Research (ICAR) has classified soils into eight distinct categories, each with unique characteristics and properties.

Types of Soil in India

Alluvial Soil

Formation: Deposited by rivers and streams, rich in minerals and fertile.
Distribution: Found in the Indo-Gangetic plains and deltas of major rivers.
Characteristics: Highly productive for agriculture due to its fertility and water-retaining capacity.

2. Black Cotton Soil

Formation: Derived from basaltic rock, rich in clay minerals (smectite), and swells when wet.
Distribution: Predominantly found in the Deccan Plateau region of central and western India.
Characteristics: Known for its ability to retain moisture and form deep cracks during dry seasons.

3. Red & Yellow Soil

Formation: Developed from weathering of crystalline and metamorphic rocks, contains iron oxides.
Distribution: Found in parts of Peninsular India and hilly regions.
Characteristics: Typically acidic, low in fertility, and prone to erosion.

4. Laterite Soil

Formation: Result of intense weathering in hot and humid tropical climates, rich in iron and aluminum oxides.
Distribution: Common in areas with heavy rainfall, such as the Western Ghats and parts of Northeast India.
Characteristics: Hard when dry, but softens and becomes slippery when wet; low in fertility.

5. Mountainous or Forest Soil

Formation: Developed under forest cover in hilly and mountainous regions.
Distribution: Found in the Himalayan foothills and other mountain ranges across India.
Characteristics: Rich in organic matter, well-drained, and conducive to forest vegetation.

6. Arid or Desert Soil

Formation: Formed in arid and semi-arid regions with low rainfall and high evaporation rates.
Distribution: Found in the Thar Desert and other arid regions of Northwestern India.
Characteristics: Low in organic matter, high in soluble salts, and prone to wind erosion.

7. Saline and Alkaline Soil

Formation: Develops in areas with poor drainage, leading to salt accumulation on the soil surface.
Distribution: Found in coastal regions, arid zones, and areas with high groundwater tables.
Characteristics: High levels of salts or alkalis, detrimental to plant growth without proper management.

8. Peaty and Marshy Soil

Formation: Accumulation of partially decomposed organic matter in waterlogged conditions.
Distribution: Found in swampy areas, marshes, and wetlands across India.
Characteristics: High organic content, acidic, and often used for wetland conservation and agriculture.

What is Soil

Soil is the loose material or the upper layer of the Earth’s crust, known as the mantle rock, consisting mainly of very small particles and humus. It provides a medium for plant growth and is vital for sustaining ecosystems.

Composition: Soil mainly consists of the following elements:

Inorganic or Mineral Fractions: These are derived from the parent material and constitute the mineral components of soil.
Organic Matter: This includes decayed and decomposed plants and animals, contributing to the nutrient content and fertility of the soil.
Air: The soil contains pores and voids filled with air, crucial for gas exchange and root respiration.
Water: Soil holds moisture in its pores, providing hydration for plants and supporting biological processes.

Formation: Soil formation, known as pedogenesis, occurs under specific natural conditions influenced by various factors:

Parent Material: The underlying rock or regolith from which soil particles are derived.
Relief: The topography or terrain of the land, influencing factors such as erosion and drainage.
Climate: Factors such as temperature, precipitation, and humidity influence the rate of weathering and organic matter decomposition.
Vegetation: Plant roots contribute to soil structure and organic matter accumulation.
Life Forms: Soil organisms such as earthworms and microorganisms play crucial roles in nutrient cycling and soil aeration.
Time: Soil formation is a gradual process that occurs over geological time scales, with soils evolving and changing over time.

Importance: Soil is essential for various ecological processes and human activities, including:

Providing a medium for plant growth and crop production.
Supporting biodiversity and ecosystem services.
Regulating water flow and nutrient cycling.
Acting as a filter for pollutants and contaminants.
Serving as a foundation for infrastructure and construction.

Soil profile

The soil profile is a vertical cross-section of the soil, consisting of distinct layers known as horizons. Each horizon exhibits unique characteristics and properties, contributing to the overall composition and structure of the soil.

Horizons

Horizon A (Topsoil)

Topmost layer of the soil profile, also known as the topsoil.
Rich in organic materials, nutrients, and water, essential for plant growth.
Represents the zone of maximum biological activity and root penetration.
Contains a mixture of mineral matter and organic matter derived from decomposition of plant and animal remains.

2. Horizon B (Subsoil)

Lies beneath Horizon A and represents the transition zone between the topsoil and the deeper layers.
Characterized by a greater concentration of mineral particles and lesser organic matter compared to Horizon A.
Contains materials leached from Horizon A as well as deposits from underlying layers.
Plays a role in nutrient storage and water movement within the soil profile.

3. Horizon C (Weathered Rock):

Composed of weathered and decomposed rock material.
Represents the initial stage in the soil formation process, serving as the source material for upper horizons.
Contains unconsolidated or loose particles derived from physical and chemical weathering of the parent rock.
Forms the foundation for the development of higher horizons through pedogenesis.

Parent Rock or Bedrock

Beneath the soil horizons lies the parent rock or bedrock.
Also referred to as the substratum, it is the solid rock layer from which the soil horizons are derived through weathering and erosion processes.
Serves as the ultimate source of mineral constituents for soil formation.

Importance: Understanding the soil profile and its horizons is crucial for

Agricultural practices such as crop selection, irrigation, and fertilization.
Land management and soil conservation efforts.
Environmental monitoring and ecosystem restoration initiatives.
Engineering projects involving foundation design and construction.

Characteristics of Soils

Different Types of Soil in India