Properties Of Soil

Key Notes :

1. Definition of Soil

  • Soil is the top layer of the Earth’s crust, composed of minerals, organic matter, air, and water.
  • It supports plant growth and is a vital part of the ecosystem.

2. Components of Soil

  • Mineral Particles: Sand, silt, and clay.
  • Organic Matter: Decayed plants and animals.
  • Water: Essential for plant growth.
  • Air: Needed by roots and soil organisms.

3. Soil Texture

  • Determined by the size of soil particles:
    • Sand: Largest particles, coarse, drains quickly.
    • Silt: Medium-sized particles, smooth texture.
    • Clay: Smallest particles, sticky, retains water.

4. Soil Structure

  • Refers to how soil particles bind together.
  • Types include granular, blocky, and platy structures.
  • Affects water retention and root penetration.

5. Soil pH

  • Indicates acidity or alkalinity of the soil.
  • Scale ranges from 0 to 14:
    • Acidic Soil: pH < 7 (e.g., forest soils).
    • Neutral Soil: pH = 7 (ideal for most plants).
    • Alkaline Soil: pH > 7 (e.g., desert soils).

6. Water Retention Capacity

  • Ability of soil to hold water:
    • Clay Soil: High retention but poor drainage.
    • Sandy Soil: Low retention, drains quickly.
    • Loamy Soil: Balanced retention and drainage, ideal for farming.

7. Permeability

  • Determines how easily water passes through soil.
  • Sand has high permeability; clay has low permeability.

8. Soil Color

  • Indicates its composition and fertility:
    • Dark Soil: Rich in organic matter.
    • Red or Yellow Soil: Contains iron oxides.
    • Pale Soil: Poor in nutrients.

9. Soil Horizons

  • Different layers in soil:
    • Topsoil (A Horizon): Rich in nutrients and organic matter.
    • Subsoil (B Horizon): Contains minerals leached from topsoil.
    • Parent Material (C Horizon): Composed of weathered rocks.

10. Soil Erosion

  • The removal of topsoil by wind, water, or human activities.
  • Prevention methods:
    • Planting vegetation.
    • Building terraces.
    • Using cover crops.

11. Importance of Soil

  • Provides nutrients for plants.
  • Stores and filters water.
  • Supports habitats for organisms.
  • Plays a role in the Earth’s carbon and nitrogen cycles.

Let’s practice!