Notes Class 7 Chapter 7 Geography Maharashtra Board

Notes For All Chapters – Geography Class 7

Soils

1. Introduction to Soil

• Soil is the uppermost layer of the Earth’s crust and is essential for plant growth.
• It is a mixture of weathered rock particles, minerals, organic matter (humus), air, and water.
• Soil formation is a long and slow natural process.
• Various factors influence soil formation, leading to different soil types across regions.

2. Factors Necessary for Soil Formation

Several factors contribute to soil formation:

(a) Parent Rock

The type of rock in a region determines the soil’s characteristics.

Rocks break down into smaller particles due to weathering.

Different parent rocks result in different soils:

• Basalt rock (found in Deccan Plateau) → Forms black soil (regur soil).
• Granite or gneiss rock (found in South India) → Forms red soil.

(b) Regional Climate

The climate (temperature, rainfall, humidity) affects weathering intensity and soil formation.

Example:

• Basalt rock in dry Deccan Plateau → Forms black soil.
• Basalt rock in humid Western Ghats → Forms lateritic soil due to heavy rainfall.

(c) Biotic Material (Organic Matter)

• Decomposed remains of plants and animals mix with weathered rock to form humus.
• Humus improves soil fertility.
• Microorganisms play a role in decomposing organic matter into nutrients.
• Organic composting techniques like vermicomposting help maintain soil health.

(d) Time

• Soil formation is a slow process and takes thousands of years.
• 2.5 cm of topsoil takes thousands of years to develop.
• Soil formation is faster in humid and warm regions compared to cold and dry areas.

3. Importance of Soil for Plants

Soil is essential for plant growth and provides:

• Nutrients for growth.
• Anchorage (support) for roots.
• Water retention for plant hydration.

Vegetation and soil fertility are interconnected:

• Equatorial regions (high rainfall) → Fertile soil → Dense forests.
• Deserts (dry regions) → Infertile soil → Sparse vegetation.
• Polar regions → Almost no soil → No vegetation.

4. Different Types of Soil in Maharashtra

Maharashtra has five major types of soil based on color, texture, formation process, and fertility.

(a) Coarse Soil

• Found in hilly areas like Ajanta, Balaghat, Mahadeo hills.
• Formed due to weathering and low rainfall.
• Contains low humus, making it less fertile.

(b) Black Soil (Regur Soil)

Found in Deccan Plateau and river valleys.

Two types:

• Dark black soil (Western Maharashtra) – Retains moisture well.
• Medium black soil (Vidarbha) – Less organic content.

Best for cotton, jowar, bajra cultivation.

(c) Laterite Soil

• Found in Konkan region & Vidarbha (high rainfall areas).
• Iron reacts with oxygen, giving it a red-orange color.
• Suitable for tea, coffee, and cashew nuts.

(d) Alluvial Soil (Coastal Region)

• Found near river mouths in Konkan.
• Formed by river deposits (sediments).
• Fertile and used for rice cultivation.

(e) Yellow-Brown Soil

• Found in Chandrapur, Bhandara, and Sahyadri mountains.
• Not very fertile, mainly used for forestry.

5. Soil Erosion and Degradation

(a) Soil Erosion

Definition: Removal of the top fertile layer of soil by wind or water.

Causes of soil erosion:

• Deforestation – Cutting down trees exposes soil to erosion.
• Overgrazing – Animals eat vegetation, leaving soil unprotected.
• Heavy rainfall and floods – Wash away the topsoil.
• Strong winds – Blow away loose soil particles.

(b) Soil Degradation

Definition: Reduction in soil fertility and productivity due to human activities.

Causes of soil degradation:

• Excessive use of chemical fertilizers & pesticides – Kills soil microorganisms.
• Over-irrigation – Leads to salinization (increased salt levels).
• Loss of organic matter – Reduces soil nutrients and humus content.

Effects of soil degradation:

• Reduced crop production.
• Decline in soil health.

6. Soil Conservation Methods

(a) Government Initiatives for Soil Conservation

• Watershed Development Programs – Construct embankments and trenches to stop erosion.
• Jalayukt Shivar Scheme – Water conservation and soil retention projects.

(b) Measures for Soil Conservation

• Afforestation (Tree Plantation) – Prevents wind erosion and holds soil in place.
• Contour Farming – Plowing across slopes to slow water runoff.
• Gully Plugging – Stopping small streams to prevent deep erosion.
• Organic Farming – Using natural manure instead of chemicals.
• Crop Rotation – Alternating crops to maintain soil fertility.

7. Geographic Indication (GI) of Soil-Based Crops

Some regions have specialized crops due to soil suitability.

Examples of GI Crops in Maharashtra:

• Hapus Mango (Sindhudurg)
• Nagpur Oranges
• Custard Apple (Beed)
• Basmati Rice (Dehradun)

8. Important Questions from the Chapter

(a) Why do the following occur?

1. Laterite soil forms in the Western Ghats due to heavy rainfall.
2. Humus content increases when organic material decomposes in soil.
3. Soil formation is faster in equatorial climates due to high rainfall.
4. Soil salinity increases due to over-irrigation.
5. Rice is the staple diet in Konkan because of alluvial soil and heavy rainfall.

(b) Give information on:

1. Measures of soil conservation (tree plantation, contour farming).
2. Organic manures (compost, vermicompost).
3. Finding soil suitability for crops (agriculture research centers).
4. Importance of soil for plant growth (nutrients, support, water retention).