Soil

Key Notes :

1. What is Soil?

  • Soil is the uppermost layer of Earth’s crust that supports plant growth.
  • It is a natural resource composed of minerals, organic matter, air, and water.

2. Formation of Soil

  • Soil formation is a slow process that occurs over thousands of years.
  • It begins with the weathering of rocks into smaller particles due to natural agents like wind, water, and temperature changes.
  • Organic material from decayed plants and animals mixes with these particles to form soil.

3. Components of Soil

  • Minerals: Provide essential nutrients for plant growth.
  • Organic Matter (Humus): Improves fertility and retains moisture.
  • Air: Helps roots to breathe.
  • Water: Essential for plant hydration and nutrient absorption.

4. Types of Soil

  • Sandy Soil: Large particles, low water retention, good drainage.
  • Clayey Soil: Small particles, retains water, poor drainage.
  • Loamy Soil: Balanced mixture of sand, silt, and clay; ideal for farming.
  • Silty Soil: Fine particles, smooth texture, retains water well.

5. Soil Horizons (Layers of Soil)

  • O Horizon: Top layer rich in organic matter (humus).
  • A Horizon (Topsoil): Contains minerals and nutrients; supports plant life.
  • B Horizon (Subsoil): Rich in minerals leached from the topsoil.
  • C Horizon: Weathered parent rock.
  • R Horizon: Unweathered bedrock.

6. Soil Erosion

  • The removal of topsoil by wind, water, or human activities.
  • Causes: Deforestation, overgrazing, and improper farming.
  • Preventive Measures: Afforestation, terracing, and crop rotation.

7. Importance of Soil

  • Supports plant growth and agriculture.
  • Regulates water flow and stores water.
  • Provides habitat for microorganisms and insects.
  • Filters and purifies water.

8. Soil Conservation

  • Mulching: Covering the soil with organic matter to retain moisture.
  • Contour Plowing: Plowing along the contour lines to prevent erosion.
  • Terracing: Building steps on slopes to reduce runoff.
  • Crop Rotation: Growing different types of crops in succession to maintain soil fertility.

9. Soil and Agriculture

  • Soil quality directly impacts crop yield.
  • Farmers use manure and fertilizers to enrich the soil with nutrients.

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