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Soil Degradation and Conservation
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Soil Degradation
 Land degradation is a huge problem today, especially for
the world’s poor
 An area equal to the size of China and India combined is
now classified as having impaired biological function
 Most the result of poor land management
 MEDCs
 Tradition of agriculture has lead to soil conserving practices
 However…sometimes climate and intensive agriculture lead to
devastating levels of erosion still
 What about LEDCs?
Processes Leading to Soil Degradation
Two Types of Processes lead to soil degradation
Processes that take away soil
Mainly due to removal of vegetation
Wind and water then remove the soil
Processes that make the soil less suitable for use
Various chemicals end up in the soil and make it useless in
the long run
Over fertilizing (salinization), various pollutants/pesticides
Human Activities Leading to Soil
Degradation
Overgrazing
Too many animals graze in the same area or
animals stay in the same area too long
Deforestation
Selective cutting: careful choosing each tree
Strip cutting: Cutting in rows
Clear cutting: Removing large areas of trees
Ex: In tropical regions leaves deflect and slow
down rain
Human Activities Leading to Soil
Degradation
Unsustainable agriculture
Total removal of crop after harvest
Having uncovered soil between rows
Plowing in the direction of the slope
Excessive Pesticides
Excessive irrigation (leads to salinization and
erosion)
Monocultures (deplete specific nutrients)
Types
Soil erosion by water
Sheet Wash
Uniform loss of soil, usually when water crosses a flat field or
mountainous region in a land slide
Gullying
Rivulets join to become larger, channel becomes wider and
deeper, usually on steeper slopes or where water moves fast
Wind erosion
On drier exposed soils the wind continually removes topsoil
Soil Conservation
 Soil Conditioners
 Most common are organic materials and lime
 Lime: Increases pH to counter soil acidification
 Also helps clay particles stick together and act more like sand
 Organics improves texture and acts as a nutrient source as well
 Wind Reduction
 Alley cropping/strip cropping
 Soil Conserving Cultivation
 Strip cropping with cover crops between rows
 Terracing (create horizontal levels on slope)
 Contour farming (Plow perpendicular to hillside)
Soil Conservation
 Improved Irrigation
 Limiting evaporation reduces salinization
 Limiting run-off reduces erosion
 Marginal Land
 Accept the fact that some land is NOT suitable for farming
 Crop Rotation
 Some crops are hungrier than others
 Rotate with a nitrogen fixer