Soil Formation and Types

Soil Formation

• Soil forms from the breakdown of rocks, called weathering, and the decomposition of organic matter from plants and animals.
• Soil is the topmost layer of the Earth, crucial for life.

Soil Fertility

• Soil fertility describes soil's ability to support plant growth.
• Factors influencing soil fertility include:
  • Moisture retention capacity
  • Soil depth for root growth
  • Nutrients like nitrogen, phosphorus, and potassium (NPK)
  • Organic matter content from plant and animal decomposition

Soil Types

• Residual Soil (In-situ soil): These remain where the parent rock formed.
  • Example: Black lava rock forms black soil in the same location.
• Transported Soil (Ex-situ soil): Forms from parent rock material moved by erosion (wind, rivers).
  • Examples: Alluvial soil from mountain sediments deposited in plains.
• Alluvial Soil:
  • Highly fertile, rich in minerals.
  • Commonly called "Silt soil," a mix of sand, clay, and silt.
  • Found in river plains (Indus, Ganges, Brahmaputra); and deltas (Mahanadi, Godavari) and coasts.
  • Subtypes:
    • Khadar: Recent flood deposits, lighter and fertile.
    • Bangar: Older, less fertile, with nodules and gravel.
• Black Soil (Regur Soil / Black Cotton Soil):
  • Forms from black lava rock weathering, rich in clay.
  • Primarily found in Maharashtra and Gujarat.
  • Fine texture, sticky, water-retentive, prone to cracking in dry seasons.
  • Suitable for cotton, jowar, wheat, sugarcane, but lacks nitrogen and phosphorus.
• Red Soil:
  • Forms from crystalline rock weathering, red from high iron oxide content.
  • Found in Tamil Nadu, Karnataka, and elsewhere.
  • Low in nitrogen, phosphorus, and potassium.
  • Lighter, airy, porous, but not highly fertile.
  • Suitable for vegetables, rice, ragi, and tobacco.
• Laterite Soil:
  • "Brick soil," easily cut into bricks.
  • Forms in regions with high rainfall and intense sun, leading to nutrient leaching.
  • Found in the Western Ghats.
  • Low fertility due to nutrient leaching, lacks humus and lime.
  • Used for construction material.
  • Suitable for tapioca, turnip, cashew, tea, and coffee.

Soil Erosion

• Topsoil removal by natural forces like wind and water.
• Types of soil erosion:
  • Sheet Erosion: Thin topsoil removal on gentle slopes.
  • Rill Erosion: Rainwater forms small channels (rills) on slopes.
  • Gully Erosion: Rills deepen, creating large channels. Most severe.
  • Stream Bank Erosion: Riverbanks erode due to water flow.
• Contributing factors:
  • Deforestation: Reduced soil holding capacity.
  • Over-grazing: Exposed soil from vegetation removal.
  • Wind Erosion: Soil movement in areas with low vegetation.

Soil Erosion Causes

• Deforestation
• Shifting cultivation
• Overgrazing
• Wind erosion
• Human population growth
• Unsustainable agricultural practices
• Monsoonal rainfall and floods
• Heavy rainfall can cause erosion.

Soil Erosion in India

• Soil erosion in India linked to outdated farming, deforestation, and geological features (water runoff, wind).
• Rajasthan and Madhya Pradesh have high erosion rates.
• High erosion regions include:
  • Jambl and Yamuna Badland
  • Western Himalayan Piedmont Zone
  • Chhota Nagpur Plateau region

Soil Conservation Techniques

• Terracing and contour planting reduce water runoff, especially in hilly areas.
• Shelterbelts (windbreaks) reduce wind velocity and erosion.
• Strip cropping (alternating crops) controls erosion.
• Dams and gully plugging manage flooding.
• Tree planting for soil cover.

Government Initiatives and Soil Conservation

• Indian government programs to combat soil erosion include:
  • Integrated Waste Management System
  • Catchment areas for flood management
  • Integrated Watersheds to manage water flow
  • Land reclamation after floods
  • Programs to discontinue shifting cultivation
• Encouraging bio-fertilizers.

Soil Conservation at the Individual Level

• Rainwater harvesting reduces runoff and replenishes groundwater.

Soil Types in India

• Various soil types across India, including:
  • Mountain Soil (Jammu and Kashmir)
  • Forest Soil (Jammu and Kashmir)
  • Alluvial Soil (Punjab, Delhi, Haryana, Uttar Pradesh, Bihar, West Bengal, Assam)
  • Red Soil (Tamil Nadu, parts of Madhya Pradesh, Odisha)
  • Black Soil (Gujarat, Maharashtra, Madhya Pradesh)
  • Laterite Soil (Western Ghats, Assam's Garo, Khasi and Jaintia Hills)
  • Arid Soil (Thar Desert)

Explore the processes behind soil formation, including weathering and organic matter decomposition. Understand soil fertility and key factors that influence it, such as nutrient content and moisture retention. Additionally, learn about different soil types and their characteristics.