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 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.
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