Overview
The lecture covers the classification and characteristics of Indian soils, focusing on alluvial and red soils, their distribution, properties, and agricultural significance.
Soil Classification in India
- Soils in India are classified into eight categories by the Indian Council of Agriculture Research (ICAR) in 1963.
- The eight soil types are: alluvial, black, red, lateritic, forest and mountain, arid and desert, saline and alkaline, and peaty/marshy soils.
Alluvial Soils
- Alluvial soil is the largest and most important soil group in India, covering 46-48% of land area (~15 lakh sq km).
- Composed primarily of fine rock particles (alluvium) deposited by rivers or sea waves.
- Rich in phosphoric acid, potash, and organic matter but lacks nitrogen, phosphate, and humus.
- Supports major crops like rice, wheat, sugarcane, cotton, jute, potato, and vegetables.
- Distribution includes Indo-Gangetic plains, Brahmaputra valleys, and coastal and delta regions.
- Two types:
- Khadar (new alluvium): found in valley bottoms, light in color, fertile.
- Bhangar (old alluvium): found higher above flood levels, black in color, contains lime nodules (kankar), less fertile.
- Special regions include Bhabar (pebbly, at Shivalik foothills) and Tarai (swampy, nitrogen-rich, below Bhabar).
Red Soils
- Red soils are red due to iron and aluminium oxides, originating from weathered granite and gneiss rocks.
- Color ranges from reddish to brownish; upland soils are thin and light, while lowland soils are deep and fertile.
- Generally poor in nitrogen, phosphorus, humus, and organic content but rich in iron and potassium.
- Soils are acidic, with texture ranging from loam to clay loam and depth from shallow to deep.
- Distribution: Tamil Nadu, southern Karnataka, southeast Maharashtra, Madhya Pradesh, Goa, Kerala, Odisha, Bihar, West Bengal, eastern Rajasthan, Assam, Manipur, Tripura, Meghalaya, Nagaland.
- Red soils account for 29% of India's soil cover and are suitable for crops like chillies, ragi, groundnut, millets, and tobacco.
Key Terms & Definitions
- Alluvium — Fine rock particles deposited by rivers or sea waves.
- Khadar — New, light-colored, fertile alluvial soil in valley bottoms.
- Bhangar — Old, dark alluvial soil found above flood plains, less fertile.
- Bhabar — Pebbly soil at Shivalik foothills.
- Tarai — Swampy, silty lowland south of Bhabar.
- Lateritic Soil — Soil rich in iron and aluminium, typically found in high rainfall areas (to be discussed later).
Action Items / Next Steps
- Review the process and factors of soil formation for an upcoming short-answer question.
- Make a table differentiating Khadar and Bhangar soils by color and properties.
- Read about black, lateritic, and other soil types for the next class.
- Note: Science class resumes after the 22nd; only geography until then.