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Soil Erosion and Salinization
Colm Parrish and Nathan
Lampenfeld
Soil Composition
• Soil is made up of four layers or horizons
– Leaf Litter (O Horizon)
– Topsoil (A Horizon)
– Subsoil (B Horizon)
– Parent Soil (C Horizon)
• Topsoil is the extremely fertile soil made
up of partially decomposed organic
matter and minerals
Human Effects on Soil
• Over the years, human farming has stripped
the amount of topsoil on arable land
• Over-plowing land can cause tillage erosion,
which was one of the main factors that led to
the Dust Bowl of the 1930s
• There is currently insufficient data to show
the effects of soil erosion on crop production
• Soil erosion, the natural process, only
becomes an issue when human activity speeds
up the process
Reason for Concern
“One reason that soil erosion is not a high
priority for many governments and farmers is
that it usually occurs so slowly that its
cumulative effects may take decades to become
apparent. For example, the loss of 1 millimeter
is so small it goes undetected. But over a 25year period the loss would be 25 millimeters,
which would take about 500 years to replace by
natural processes.”
-David Pimentel
The New Dust Bowl
• In China, massive amounts of over plowing
and over grazing is causing massive wind
erosion
• Creates huge plumes of dust
– Reduces visibility in northeast Chinese cities
– Causes visibility reduction and air pollution in
Japan, Korea, and the Northwest United
States
Climate Change and Erosion
• Climate change is bringing colder, or warmer,
temperatures to soil. Soil moisture levels are
very low at the surface of excessively drained
soils or during periods of drought. This
releases particles of soil to be carried away by
wind. This effect also occurs in freeze-drying
of the soil surface during winter months.
• Climate change is also anticipated to have
great effects on the water cycle, which
directly effects soil erosion by water
Desertification
• The productive topsoil of arid or semiarid
land falls by 10 percent due to human and
natural causes
– Prolonged drought
– Reduction of topsoil due to human activities
• According to the UN, about 40 percent of
the world’s land is suffering from
desertification
Ways to Prevent Soil Erosion
• There are various ways to prevent soil erosion
– Windbreaks prevent wind erosion
– Methods to prevent water erosion
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Terracing
Contour Farming
Strip Cropping
Alley cropping
Gully reclamation
• In order to regain topsoil, organic fertilizers
such as manure and compost should be used
The Importance of Plants
• Locally indigenous plants are more
efficient at creating roots in soil, holding
the soil in place, than imported crops
• Plants slow down the running off of water,
allowing the soil to absorb it
• Plants break te impact of rain on soil,
slowing down erosion
Salinization
• Caused by irrigation, excess salts create a
crust over topsoil
• Waterlogging occurs when the plants are
over watered, and the water table rises.
The saline water then envelops the deep
roots, killing the plant
• Only way to treat salinization is flushing,
underground drainage, or not growing on
the land for several years