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Physical causes of soil degeneration are;Poor land-use practices such as overgrazing/overstockingHeavy use of farm machinery in land preparation interferes with the soil structure and texture.Overcultivation of landProlonged/excessive droughtExcessive soil erosion
Roles of living organisms in soil formation are;Decompose organic matter to humus (bacteria and fungi)Fix nitrogen in the soil (Rhizobium bacteria)Provide nutrients in the soil when they dieTheir waste matter adds nutrients to the soilTheir burrowing activities increase the breakdown of rock particlesPlant roots breakdown rocks as they grow and expand.Larger animals break rock particles increasing the process of weathering.
Factors influencing soil formation are;Parent rock materialClimateTopography/reliefTimeOrganic influence e.g living organisms
Physical characteristics used in classification of soil are;Soil textureSoil structureSoil color
Causes of soil creep are;Ploughing across a slope causing the rocks to turn towards the lower sides of the slope.Freezing of soil water causing it to expand which lifts particles at right angles to the slope.Rainwater which percolates into the soil making them to change their positions.Removing soil downslope causing them to shift theri position under the influence of gravity.Trampling and burrowing of animals loosening soil particles causing them move downslopeExternal forces e.g shaking by earthquakes, explosives and heavy trucks causing soil to move downslope.Alternate and cooling causing expansion and contraction of particles causing them to change their position.