Soil Erosion and Degradation

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					Soil Erosion and
     Degradation
    Soil Erosion and Degradation
   PA Standards                        Analyze factors that
       4.2.12.C: Renewable and          influence the availability
        Nonrenewable Resources
                                         of natural resources.
       4.4.10.B: Agriculture and
        Society                         Assess the influence of
                                         agriculture science on
                                         farming practices
                                         (plowing).
“The nation that destroys its
  soil destroys itself.”
    - Franklin D. Roosevelt (1937)
Key Questions
   How are soils being degraded and eroded?
   What can be done to reduce these losses?
Consider this…

   Human activity accelerates natural soil
    erosion.



   One-third to one-half of world’s croplands are
    losing topsoil faster than it is being renewed
    by natural processes .
HOW MUCH OF THE EARTH IS
AVAILABLE FOR FARMING?
   Question: How much of the Earth is available
    for farming?



   http://www.agclassroom.org/teacher/screens
    avers/apple.htm
  How are soils being
degraded and eroded?
SOIL EROSION AND
DEGRADATION
   Soil erosion lowers soil fertility and can
    overload nearby bodies of water with eroded
    sediment.
       Sheet erosion: surface water or wind peel off thin
        layers of soil.
       Rill erosion: fast-flowing little rivulets of surface
        water make small channels.
       Gully erosion: fast-flowing water join together to
        cut wider and deeper ditches or gullies.
SOIL EROSION AND
DEGRADATION
                              Soil erosion is the
                               movement of soil
                               components,
                               especially surface
                               litter and topsoil, by
                               wind or water.
   Soil erosion increases through activities such
    as farming, logging, construction, overgrazing,
    and off-road vehicles.
    Global Outlook: Soil Erosion




   Soil is eroding faster than it is forming on more
    than one-third of the world’s cropland.
 What can be done to
reduce these losses?
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
   Modern farm machinery can plant crops
    without disturbing soil (no-till and minimum
    tillage.
       Conservation-tillage farming:
           Increases crop yield.
           Raises soil carbon content.
           Lowers water use.
           Lowers pesticides.
           Uses less tractor fuel.
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
                 Terracing, contour
                  planting, strip
                  cropping, alley
                  cropping, and
                  windbreaks can
                  reduce soil erosion.
Biodiversity Loss              Soil                Water              Air Pollution        Human Health
Loss and              Erosion             Water waste                 Greenhouse gas       Nitrates in
degradation of                                                        emissions from       drinking water
                      Loss of fertility   Aquifer depletion           fossil fuel use
grasslands,
forests, and          Salinization        Increased runoff and                             Pesticide residues
wetlands                                  flooding from cleared       Other air pollutants in drinking water,
                      Waterlogging        land                        from fossil fuel use food, and air
Fish kills from       Desertification     Sediment pollution from
                                          erosion                     Greenhouse gas       Contamination of
pesticide runoff                                                                           drinking and
                                                                      emissions of
                                          Fish kills from pesticide   nitrous oxide from   swimming water
Killing wild predators to                 runoff                      use of inorganic     with disease
                                                                      fertilizers          organisms from
protect livestock                         Surface and groundwater                          livestock wastes
                                          pollution from pesticides
                                          and fertilizers           Belching of the
Loss of genetic diversity of
                                                                    greenhouse gas         Bacterial
wild crop strains replaced                Overfertilization of      methane by cattle
                                          lakes and rivers from                            contamination of
by monoculture strains                                                                     meat
                                          runoff of fertilizers,
                                          livestock wastes, and     Pollution from
                                          food processing wastes pesticide sprays
Review Key Questions
   How are soils being degraded and eroded?
   What can be done to reduce these losses?
Thought Problems
   How does deforestation, over farming, and over grazing contribute to erosion or
    arable land?


   If we exhaust the food-producing resources we have now, won’t science devise
    new ways to increase food production as it has been done in the past?


   What conclusions can we draw about the relationship between a growing
    population and a shrinking amount of land capable of growing food for those
    people?


   How can we preserve farmland?
Thought Problems - Answers
   How does deforestation, over farming, and over grazing contribute to erosion or
    arable land?
       1/32 of land is suitable for agriculture; deforestation increases erosion, over farming
        decreases land nutrients, and over grazing increases erosion and decreases nutrients

   If we exhaust the food-producing resources we have now, won’t science devise
    new ways to increase food production as it has been done in the past?
       Hydroponics; genetics; decrease nutrients, decrease health in livestock; increase in
        antibiotics

   What conclusions can we draw about the relationship between a growing
    population and a shrinking amount of land capable of growing food for those
    people?
       Famine; decreased nutrients; different types of food

   How can we preserve farmland?
       No plow farming; stop wasting, rotate crops; conservation tillage, best management
        practices; limit development; buy local; eat lower on the food chain
Case Study: Soil Erosion in the
U.S. – Some Hopeful Signs

   Soil erodes faster than it forms on most U.S.
    cropland, but since 1985, has been cut by
    about 40%.
       1985 Food Security Act (Farm Act): farmers
        receive a subsidy for taking highly erodible land
        out of production and replanting it with soil saving
        plants for 10-15 years.
    Desertification: Degrading
    Drylands




   About one-third of the world’s land has lost
    some of its productivity because of drought and
    human activities that reduce or degrade topsoil.
Moderate   Severe   Very severe
Salinization
and
Waterlogging

   Repeated
    irrigation can
    reduce crop yields
    by causing salt
    buildup in the soil
    and waterlogging
    of crop plants.
                       Solutions

                    Soil Salinization

Prevention                              Cleanup


Reduce irrigation                       Flush soil
                                        (expensive and
                                        wastes water)



                                        Stop growing crops
                                        for 2–5 years


Switch to salt-                         Install underground
tolerant crops                          drainage systems
(such as barley,                        (expensive)
cotton,
sugarbeet)
Salinization and Waterlogging of
Soils: A Downside of Irrigation

                        Example of high
                         evaporation,
                         poor drainage,
                         and severe
                         salinization.
                        White alkaline
                         salts have
                         displaced cops.
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
   Fertilizers can help restore soil nutrients, but
    runoff of inorganic fertilizers can cause water
    pollution.
       Organic fertilizers: from plant and animal (fresh,
        manure, or compost) materials.
       Commercial inorganic fertilizers: Active
        ingredients contain nitrogen, phosphorous, and
        potassium and other trace nutrients.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT




   Since 1950, high-input agriculture has produced
    more crops per unit of land.
   In 1967, fast growing dwarf varieties of rice and
    wheat were developed for tropics and
    subtropics.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
   Lack of water, high costs for small farmers, and
    physical limits to increasing crop yields hinder
    expansion of the green revolution.
   Since 1978 the amount of irrigated land per
    person has declined due to:
       Depletion of underground water supplies.
       Inefficient irrigation methods.
       Salt build-up.
       Cost of irrigating crops.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
   Modern agriculture has a greater harmful
    environmental impact than any human activity.
   Loss of a variety of genetically different crop and
    livestock strains might limit raw material needed
    for future green and gene revolutions.
       In the U.S., 97% of the food plant varieties available
        in the 1940 no longer exist in large quantities.

				
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posted:12/18/2011
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