Soil: Earth’s Life-Sustaining Blanket
Chapter 9 of the NCERT 7th Grade Science textbook introduces us to the magnificent realm of soil. Beyond just dirt and mud, soil is a living entity teeming with microorganisms, minerals, and organic matter. Let’s uncover the secrets of this life-sustaining layer of the Earth.
Understanding Soil
Soil is a natural resource, vital for sustaining life on Earth. It’s more than just earth; it’s a complex mixture of weathered rock fragments, organic material, water, and air.
Soil Formation
The process of soil formation is called weathering. It’s a slow and gradual process where rocks break down into smaller particles due to physical, chemical, and biological factors. Factors affecting weathering include:
- Temperature variations
- Wind
- Water
- Lichens and mosses
Components of Soil
- Minerals: The inorganic fraction derived from rocks.
- Organic Matter: Decayed remains of plants and animals.
- Soil Water: Essential for plant growth; it dissolves nutrients.
- Soil Air: Present in the pores between soil particles.
Soil Profiles and Horizons
A vertical section through different layers of the soil is called its profile. These layers are termed as ‘horizons’.
- Horizon A (Topsoil): Rich in humus and minerals. Dark in color.
- Horizon B (Subsoil): Accumulates materials leached from above layers.
- Horizon C: Resembles parent rock. Contains broken rock fragments.
Types of Soil
- Sandy Soil: Coarse particles; facilitates good aeration. Poor in nutrients.
- Clayey Soil: Fine particles; retains water. Rich in organic matter.
- Loamy Soil: Balanced mix of sand, clay, and silt. Ideal for farming.
Properties of Soil
- Permeability: Ability of soil to transmit water.
- Moisture: Amount of water present in the soil.
- pH Level: Measures the acidity or alkalinity of soil.
Soil and Crops
Different crops require specific soil types. For instance:
- Wheat: Grows best in loamy soil.
- Paddy: Prefers clayey soil which can hold water.
Soil Erosion and Conservation
Soil erosion is the removal of the fertile top layer due to wind or water. Conservation methods include:
- Contour Ploughing: Plowing parallel to contours of the land.
- Terrace Farming: Creating flat areas in hilly regions.
- Afforestation: Planting trees reduces soil erosion.
Importance of Soil
Soil not only supports plant growth but also houses countless microorganisms. It acts as a natural filter, cleaning underground water, and is a reservoir of essential minerals.
Conclusion: Celebrating Earth’s Vital Layer
“Soil” from NCERT’s Grade 7 Science is a tribute to Earth’s nurturing layer. With its rich composition, varied types, and immense benefits, soil remains a treasure that we need to cherish and preserve. As stewards of our planet, understanding and protecting our soil is paramount.
