Soil Resources – Types, Erosion, and Conservation

Soil as a Resource: Soil is the most important renewable natural resource. It is the medium of plant growth and supports different types of living organisms on Earth.

• • Formation: Takes millions of years to form a few centimeters of soil.

  • Factors of Formation: Relief, parent rock or bedrock, climate, vegetation, and other forms of life and time are important factors. Various forces of nature like changes in temperature, actions of running water, wind, glaciers, activities of decomposers, etc., contribute to soil formation.

• Classification of Soils (Major Types in India):

  • Alluvial Soils:

    • Most widespread and important soil.

    • Formed by deposits of river systems (Indus, Ganga, Brahmaputra).

    • Found in northern plains, also in deltas of Mahanadi, Godavari, Krishna, and Kaveri rivers.

    • Consist of sand, silt, and clay.

    • Two types:

      • Bhangar: Old alluvial soil, coarser, contains Kankar nodules, less fertile.

      • Khadar: New alluvial soil, finer, more fertile.

    • Very fertile, ideal for sugarcane, paddy, wheat, and cereal/pulses.

    • Highly productive and densely populated regions.

  • Black Soils (Regur Soils):

    • Characteristic of the Deccan Trap region.

    • Made up of lava flows, found in Maharashtra, Madhya Pradesh, Chhattisgarh, and the plateaus of Krishna and Godavari valleys.

    • Ideal for growing cotton, also known as black cotton soil.

    • Clayey material, well-known for moisture retention.

    • Rich in calcium carbonate, magnesium, potash, and lime, but poor in phosphoric content.

    • Develop deep cracks during hot weather (aids aeration), sticky when wet, difficult to work unless tilled immediately after monsoon rains.

  • Red and Yellow Soils:

    • Develop on crystalline igneous rocks in areas of low rainfall (eastern and southern parts of Deccan Plateau).

    • Found in parts of Odisha, Chhattisgarh, southern parts of the Middle Ganga Plain, and along the Piedmont zone of the Western Ghats.

    • Red colour due to diffusion of iron in crystalline and metamorphic rocks.

    • Looks yellow when in a hydrated form.

  • Laterite Soils:

    • Develop under tropical and subtropical climates with alternating wet and dry seasons.

    • Result of intense leaching due to heavy rain (leaching means removal of soluble components by percolating water).

    • High acidity, low fertility (due to removal of humus).

    • Commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh, and hilly areas of Odisha and Assam.

    • Suitable for cashew nuts. Requires manures and fertilisers for cultivation.

  • Arid Soils:

    • Ranges from red to brown in colour.

    • Sandy texture, saline nature.

    • Lack humus and moisture due to dry climate and high temperature.

    • Kankar layer formation in the lower horizons restricts water infiltration.

    • Found in western Rajasthan. Can be made cultivable after proper irrigation.

  • Forest Soils:

    • Found in hilly and mountainous areas.

    • Vary in texture and structure depending on the mountain environment.

    • Loamy and silty in valley sides, coarse-grained in upper slopes.

    • Acidic with low humus content in snow-covered areas; fertile in lower parts of valleys (e.g., along river terraces, alluvial fans).

• Soil Erosion and Soil Conservation:

  • Soil Erosion: The denudation of the soil cover and subsequent washing down.

    • Caused by human activities (deforestation, overgrazing, construction, mining, faulty farming methods) and natural forces (wind, glacier, water).

    • Gullies: Deep channels formed by running water, making the land unfit for cultivation (bad land).

    • Sheet Erosion: Water flows as a sheet over large areas down a slope, washing away the topsoil.

    • Wind Erosion: Wind blows loose soil off flat or sloping land.

    • Ploughing Methods: Defective methods of ploughing can lead to soil erosion (e.g., ploughing up and down the slope creates channels for water flow).

  • Soil Conservation Measures:

    • Contour Ploughing: Ploughing parallel to contours of a hill slope to reduce water flow down the slope.

    • Terrace Cultivation: Steps cut out on the slopes to restrict erosion; common in western and central Himalayas.

    • Strip Cropping: Large fields divided into strips; strips of grass are left to grow between the crops to break up the force of the wind.

    • Shelter Belts: Rows of trees planted to create shelter and reduce wind erosion, particularly in coastal and dry regions.

    • Integrated Approaches: Combining different measures for effective soil conservation.