soil erosion & degradation soil erosion: movement of soil components, especially litter & topsoil,...

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  • Soil Erosion & DegradationSoil erosion: movement of soil components, especially litter & topsoil, from one place to another.

    losing topsoil makes soil less fertile & less able to hold water;while soil is a potentially renewable resource, it takes long periods of time to form topsoil, typically 2001000 years to form 2.5 centimeters (1 inch) of topsoil;topsoil is eroding faster than it forms in about onethird of the world's cropland.

  • Soil Erosion & DegradationMajor areas of the world are threatened by serious soil erosion.

  • Soil Erosion & Degradation Farming practices such as plowing and tilling can leave soil uncovered and loose. These practices leaves soil vulnerable to water and wind erosion.TillingDisk Harrow

  • Soil Erosion & Degradation: Wind & Water

  • Soil Erosion & Degradation

  • Dust BowlDuring the 1930s, a combination of drought & poor soil conservation led to severe wind erosion of topsoil in what is known as the Dust Bowl of the Great Plains.

  • Causes:overgrazing;deforestation & devegetation;surface mining;poor irrigation techniques;salt buildup;farming on unsuitable terrain;soil compaction by farm machinery.Desertification of arid & semiarid lands results when land productivity drops markedly.

  • Dust StormsDust Devil

  • Dust Storms

  • Dust Storms

  • Dust StormsAsiaSaudi ArabiaSahara

  • Problems of Irrigation:

    Salinization: salt build-up in irrigated lands to levels that decrease crop yields.

  • Problems of Irrigation:Waterlogging results when excess irrigation water raises the water table & lowers crop productivity.

  • Types of erosion: Sheet Erosion: Surface water runs down a slope and erodes layers of topsoil off; Rill Erosion: fast-flowing water cuts small rivulets or channels in soil; Gully Erosion: rivulets become bigger and join to form gullies

  • Soil conservation: reducing soil erosion & restoring soil fertility.

    conservationtillage farming minimizes soil disturbance. use of special tillers which loosen subsurface soil without turning over top soil and residues; notill methods that inject seeds, fertilizers, & herbicides in unplowed soil; By maintaining a layer of crop residue on 30 % or more of the surface, reduces water erosion.

    Crop residue

  • Soil Conservationterracing protects steep slopes; retains water for crops at each level and reduces erosion by controlling runoff;contour farming follows natural land contours; each row of crops acts as a dam to slow water runoff down slopes

  • Soil Conservationstrip cropping maintains strips of different vegetation between crops; keeps soil covered, slows erosion, and some nitrogen-fixing plants ( such as legumes) can increase fertility.

  • Soil Conservationalley cropping grows crops between rows of trees: The result is better erosion control, improved crop production, supplemental income, and habitat and travel corridors for wildlife.

  • Soil Conservationwind breaks uses trees between fields to slow wind erosion use of organic fertilizer (manure, "green manure" = plant matter, & compost);

  • Soil Conservation crop rotation :planting crops that restore nutrients; & decrease in use of inorganic fertilizers all help to restore fertility.

  • Soil ConservationGood irrigation techniques can help slow wind and water erosion without waterlogging, causing excess runoff, or depleting water supplies Grass in waterway slows water erosion.

  • Soil Erosion & Degradation