A vertical section through different layers of the soil is called the soil profile. Soil consists of three horizontal layers. They are true soil at the top, sub soil, and bedrock
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Soil Profile of India: Layers, Types, and Agricultural Importance
Soil is the topmost layer of the Earth's crust, primarily composed of organic materials and rock particles, and plays a crucial role in supporting life.
Soil Profile
A soil profile is a vertical cross-section of the soil that displays various layers called soil horizons.
Understanding Soil Horizons
A soil profile is a vertical section through the different layers of soil, known as soil horizons.
The soil is typically divided into three horizontal layers:
Topsoil (True Soil)
Subsoil
Bedrock
Each horizon varies in texture, colour, depth, and chemical composition.
These layers are formed through internal processes such as leaching and capillary action (upward movement of water and minerals).
Soil profiles are analyzed by extracting samples in the form of a hexagonal column.
Soil Horizon Layers
Soil Horizon refers to a layer of soil that exhibits distinct physical characteristics, including colour and texture, different from the layers above and below it.
Soil Profiles and Horizon
The topsoil or A-horizon is typically dark due to its rich content of humus and minerals.
The B-horizon is the middle layer, rich in minerals but with less organic content than the A-horizon.
The C-horizon consists of parent material, made up of weathered rocks and minerals.
Components of Soil Profile
The soil profile extends from the soil surface down to the bedrock (parent material).
The regolith represents all weathered material within the profile, divided into two key components:
Solum: The uppermost, most weathered portion of the soil profile.
Saprolite: The least weathered portion, located just above the bedrock.
Components of Soil Profile
Types of Soil Horizons
Soil horizons are formed through interactions between climate, organisms, and the land surface over time.
These layers are shaped by selective leaching, ion removal, and mineral accumulation, resulting in two broad types:
Organic Horizons (O): Composed primarily of decomposed plant and animal matter.
Mineral Horizons: Includes A, E, B, and C horizons, which are rich in inorganic minerals.
Detailed Horizon Breakdown
Four Main Mineral Horizons
O Horizon: Dominated by organic material, consisting of decomposed plant litter and humus.
A Horizon (Topsoil): The layer rich in both organic and mineral content, providing the essential nutrients for plant growth.
E Horizon: The eluviated layer, which has been leached of its nutrients, making it poor in minerals.
B Horizon (Subsoil): The subsoil, where minerals leached from the upper layers accumulate.
C Horizon: Made up of weathered rock fragments and material that are the foundation of soil formation.
R Horizon: The bedrock layer located beneath the soil profile, from which the soil derives its mineral content.
Significance of the Soil Profile
The study of soil profiles is critical for agriculture, as it helps determine land suitability for various crops.
Soil profiles are integral to land classification and understanding how different layers support plant growth, water retention, and mineral availability.
Knowledge of soil horizons is also crucial for soil conservation and improving soil fertility for sustainable farming.
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