FORM 3 - GEOGRAPHY NOTES >> SOIL TOPIC ] READ ON THIS TOPIC

🌍 SOIL – An Overview

Definition:
Soil is the uppermost layer of the earth’s crust that supports plant growth. It is a natural body composed of minerals, organic matter, water, air, and living organisms.

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🌱 Composition of Soil

1. Mineral matter (45%) – sand, silt, clay

2. Organic matter (5%) – humus, decomposed plants/animals

3. Water (25%) – soil moisture for plant growth

4. Air (25%) – oxygen and other gases for roots & organisms

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🌿 Soil Formation (Pedogenesis)

Soil forms through the weathering of rocks and the decay of organic matter. Factors affecting formation:

• Parent material

• Climate

• Living organisms

• Topography

• Time

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🏞️ Soil Profile (Horizons)

1. O-horizon – organic layer (humus)

2. A-horizon – topsoil, rich in nutrients

3. B-horizon – subsoil, minerals accumulate

4. C-horizon – weathered parent rock

5. R-horizon – bedrock

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🌍 Types of Soil (by texture)

• Sandy soil – coarse, drains quickly, poor nutrients

• Clay soil – fine particles, holds water, poor drainage

• Silty soil – smooth, fertile, moderate drainage

• Loamy soil – balanced mix, best for agriculture

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🌾 Importance of Soil

• Basis for agriculture (crop growth)

• Habitat for organisms

• Source of raw materials (clay, sand, minerals)

• Water filtration & storage

• Carbon storage & climate regulation

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⚠️ Soil Problems

• Soil erosion (wind, water)

• Soil pollution (chemicals, waste)

• Soil degradation (deforestation, overgrazing, over-farming)

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🌍 Soil Conservation Methods

• Afforestation & reforestation

• Contour ploughing

• Terracing

• Crop rotation

• Use of organic manure & cover crops

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