Soil erosion, Degrada-tion and conservation | Biogeography | Principle Of Geography

 

Biogeography

Principle Of Geography

Geography Complete Study Material

(Paper - I)

Soil erosion, Degradation and Conservation

Soil erosion  

      The destruction of the soil cover is described as soil erosion. The soil forming processes and the erosional processes of running water and wind go on simultaneously. But generally, there is a balance between these two processes. The rate of removal of fine particles from the surface is the same as the rate of addition of particles to the soil layer.

         Sometimes, such a balance is disturbed by natural or human factors, leading to a greater rate of removal of soil. Human activities too are responsible for soil erosion to a great extent. As the human population increases, the demand on the land also increases. Forest and other natural vegetation is removed for human settlement, for cultivation, for grazing animals and for various other needs.

 

TYPES OF SOIL EROSION 

       Soil erosion is classified on the basis of the physical agent responsible for erosion. The various types of soil erosion are consequently referred to as: (a) Water erosion (b) Wind erosion. 

(a) Water erosion 

       Running water is one of the main agents, which carries away soil particles. Soil erosion by water occurs by means of raindrops, waves or ice. Soil erosion by water is termed differently according to the intensity and nature of erosion.

• (i) Raindrop erosion 
• (ii) Sheet erosion 
• (iii) Rill erosion 
• (iv) Steam banks erosion 
• (v) Erosion due to land slides 
• (vi) Coastal erosion

(b)Wind erosion 

      Soil erosion by wind is more common in areas where the natural vegetation has been destroyed. Such conditions occur mainly in arid and dry areas along the sandy shores of oceans, lakes and rivers. The loose soil particles are blown and transported from wind by following three ways: 

• (i) Siltation: blown by wind in a series of short bounces. 
• (ii) Suspension: transported over long distances in the form of suspended particles. 
• (iii) Surface creep: transported at ground level by high velocity winds. 

Consequences of soil erosion: 

• 1. The fine particles of the topsoil which contain the bulk of nutrients and organic matter needed by the plants are lost from soil erosion. Erosion removes the most fertile part of soil. The less fertile subsoil is left. 
• 2. Erosion may result in removal of seeds or seedlings so that the soil becomes bare. Bare soil is more vulnerable to erosion both by wind and water. 
• 3. Removal of seeds and seedlings reduces the ability of soil to store water. 
• 4. Sheet, rill, gully and stream bank erosion also cause siltation of rivers, streams and fields. Deposition of silt results in damage of crops and pastures, and sedimentation of water bodies like streams, dams, reservoirs etc. 
• 5. Sedimentation of water bodies deteriorate water quality and damage aquatic habitats and organisms. 
• 6. Gully erosion also results in loss of large volumes of soil. Wider deep gullies sometimes reach 30 m and thus severely limit land use. 
• 7. Large gullies disrupt normal farm operation.
• 8. Stream bank erosion not only causes loss of land, but also changes the course of a river or stream. 
• 9. Stream banks erosion also damage public roads. 
• 10. Mass movement of land or landslides also inhibits farm production and land use. 
• 11. It also causes mortality in animals and humans. 
• 12. Coastal erosion causes the adjourning land to become covered by sand.

Degradation of Soil and Conservation Measures 

        Soil erosion and depletion are the major threats to soil as a resource. Both human and natural factors can lead to degradation of soils. Factors which lead to soil degradation are deforestation, overgrazing, overuse of chemical feritilisers or pesticides, rain wash, landslides and floods. Some methods of soil conservation are listed below:

• Mulching: The bare ground between plants is covered with a layer of organic matter like straw. It helps to retain soil moisture. 
• Contour barriers: Stones, grass, soil are used to build barriers along contours. Trenches are made in front of the barriers to collect water. 
• Rock dam: Rocks are piled up to slow down the flow of water. This prevents gullies and further soil loss.
• Terrace farming: Broad flat steps or terraces are made on the steep slopes so that flat surfaces are available to grow crops. They reduce surface runoff and soil erosion. 
• Intercropping: Different crops are grown in alternate rows and are sown at different times to protect the soil from rain wash. 
• Contour ploughing: Ploughing parallel to the contours of a hill slope to form a natural barrier for water to flow down the slope. 
• Shelter belts: In the coastal and dry regions, rows of trees are planted to check the wind movement to protect soil cover.