NCERT · Class 10 · Social Science · Geography: Resources and DevelopmentDescribe the main characteristics and geographical distribution of Alluvial Soil and Black Soil in India.

1. Alluvial Soil (जलोढ़ मृदा)

\nAlluvial soil is the most widely spread and important soil found in India. It covers about 40% of the total land area of the country.

• Main Characteristics:
  • Formation: Formed by the deposition of silt brought down by major river systems—the Indus, the Ganga, and the Brahmaputra.
  • Nutrient Content: Rich in potash, phosphoric acid, and lime, which are ideal for the growth of sugarcane, paddy, wheat, and pulses. However, it is generally poor in nitrogen.
  • Age-based Classification:
    • Bangar: Old alluvial soil, higher in Kankar (nodules) content, less fertile.
    • Khadar: New alluvial soil, fine particles, more fertile.
  • Textural Quality: Highly fertile and extensively cultivated, supporting high population density.
• Geographical Distribution:
  • Dominantly spread in the Northern Plains (Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, and Assam).
  • Found in the coastal plains of eastern India, particularly in the deltas of the Mahanadi, the Godavari, the Krishna, and the Kaveri rivers.

2. Black Soil / Regur Soil (काली मृदा)

\nBlack soil is also known as Regur Soil or Black Cotton Soil because it is ideally suited for growing cotton.

• Main Characteristics:
  • Formation: Derived from the weathering of basaltic rocks (lava flows) under climatic conditions of high temperature and low rainfall.
  • Moisture Retention: Made up of extremely fine clayey material with a high capacity to hold moisture.
  • Nutrient Content: Rich in soil nutrients such as calcium carbonate, magnesium, potash, and lime, but deficient in phosphoric content.
  • Self-Ploughing Nature: Develops deep cracks during hot dry weather, which helps in proper aeration of the soil. When wet, it becomes sticky and difficult to work unless tilled immediately after the first shower.
• Geographical Distribution:
  • Typical of the Deccan Trap (Basalt) region spread over the northwest Deccan plateau.
  • Covers the plateaus of Maharashtra, Saurashtra, Malwa, Madhya Pradesh, Chhattisgarh, and extends southeast along the Godavari and Krishna valleys.