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1Corinne Waelti, seecon international gmbh Soil DegradationCorinne Waelti, seecon international gmbh
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3Contents1. Introduction2. Four Types of Soil Degradation3. Human Causes of Erosion4. Controlling Erosion5. Conclusion6. References
41. Introduction What is soil degradation? The overall ProblemWhat is soil degradation?Process by which one or more of the potential ecological functions of the soil are harmed or destroyed.Soil degradation is an increasing global process affecting mainly arid and semi-arid zones in sub-Saharan Africa. Principal forms are the depletion of nutrients and soil organic matter and erosion.The negative impacts of soil degradation may lead to partial or complete loss of the soil’s current and/or future productive capacity. Soil degradation can be a result of both natural hazards and unsuitable land use.
5Four Types of Soil Degradation 1. IntroductionFour Types of Soil DegradationWater erosionWind erosionSoil degradationSource: PLANT and SOIL SCIENCES ELIBRARY (2005)Source: RITTER (2003)Chemical deteriorationPhysical deteriorationSource:Source:
6A global Problem: Human induced Soil Degradation 1. IntroductionA global Problem: Human induced Soil DegradationISRIC et al. (1996)
72. The Four Types of Soil Degradation Water Erosion (1/2)Soil particles, which are either detached by splash erosion or by the effect of running water.Factors influencing water erosionRainfallThe impact of raindrops on the soil surface can break down soil aggregates and disperse the aggregate material over the surface.Soil typeSoils with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion.Slope gradientSteeper and longer slopes of a field lead to greater amount of soil erosion by water.Soil usePlants may protect the soil from raindrop impact and splash, slow down the movement of surface runoff and allow infiltration of excess surface water.BALLAYAN (2000) and INFONET-BIOVISION (2010)
82. The Four Types of Soil Degradation Water Erosion (2/2)Types of water erosionSheet erosionRemoval of a fairly uniform layer of soil from an entire surface area.Rill erosionSmall channels running over the soil surface causing deeper incision of the channels into the surface.Gully erosionRills flowing together form larger streams and tend to become deeper with successive flow of water.Bank erosionWater cutting into the banks of streams and rivers.BALLAYAN (2000)
92. The Four Types of Soil Degradation Wind ErosionFactors influencing wind erosionSoil erodibilityFine and medium soil particles can be transported over great distances. Coarse particles can be blown along the surface.Soil surface roughnessSoil surfaces that are not rough or ridged offer little resistance to the wind.ClimateSoil moisture levels can be very low at the surface during periods of drought, thus releasing particles for transport by wind.Vegetative coverThe lack of permanent vegetation cover may lead to extensive erosion by wind as loose, dry and bare soil is most susceptible.SHELTON (2003)
10Chemical Deterioration 2. The Four Types of Soil DegradationChemical DeteriorationTypical causesMunicipal or industrial wastesOil spillsExcessive use of fertiliser, herbicides and insecticidesRelease of radioactive materialsAirborne pollutantsEffectsLoss of nutrients and organic matter leading to reduced plant growthSalinisationAcidificationSoil pollutionFertility declineFAO/AGL (2000)
11Physical Deterioration 2. The Four Types of Soil DegradationPhysical DeteriorationTypical causeCompaction through heavy machines or animalsEffectsSoil crustingIncreased runoffDecreased infiltration of water into the soilPrevention and inhibition of plant growthHigher susceptibility to other forms of degradationFAO/AGL (2000)
12Human Actions leading to Soil Degradation 3. Human Causes of ErosionHuman Actions leading to Soil DegradationPoor agricultural practicesExposing soil on slopesRemoval of forest vegetationOvergrazingAltering the characteristics of streams, causing bank erosionReducing evapotranspiration losses due to vegetation removalProducing impervious surfaces such as roads and footpaths causing increased runoff into streamsOverexploitation of groundwaterACS DISTANCE EDUCATION (2009)
13The most common Control Methods 4. Controlling ErosionThe most common Control MethodsCover materials (e.g. plants)Improved crop production techniques (e.g. organic fertiliser, type of irrigation method)Ploughing to destroy rills and contour plantingTerracingCareful selection of land use practicesConservation tillage methodsArmouring of channels to prevent bank erosionWind breaksPloughing into clod sizes too big to be eroded / Ploughing into ridges Sustainable Agriculture / Land ManagementACS DISTANCE EDUCATION (2009)
14Sustainable Land Management is crucial 5. ConclusionSustainable Land Management is crucialNo sustainable land managementChanges with sustainable land managementSustainable land managementDegraded soilWorld populationAvailable landFood demandFood production
156. ReferencesACS DISTANCE EDUCATION (Editor) (2009): Soil Degradation. Stourbridge: ACS Distance Education. URL: [Accessed: ].BALLAYAN, D. (2000): Soil Degradation. ESCAP environment statistics course. Rome: FAO. URL: [Accessed: ].FAO (Editor), AGL (Editor) (2000): Management of Degraded Soils in Southern and eastern Africa (MADS-SEA-Network). Rome: FAO.INFONET-BIOVISION (Editor) (2010): An Introduction to soil degradation. Zurich: Biovision. URL:http://www.infonet-biovision.org/default/ct/184/soilManagement [Accessed: ].ISRIC (Editor), UNEP (Editor), FAO (Editor) (1996): Human Induced Soil Degradation. Rome: World Food Summit. URL: [Accessed: ].PLANT (Editor), SOIL SCIENCES ELIBRARY (Editor) (2005): Picture of Gully Plug Erosion. University of Nebraska-Lincoln. URL: [Accessed: ].RITTER (2003): The Physical Environment. An Introduction into Physical Geography. URL: [Accessed: ].SHELTON, I. J. (2003): Soil Erosion – Causes and Effects. Ridgetown College of Agricultural Technology. Ontario Institute of Pedology. URL: [Accessed: ].
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