Unit 3 lesson 5 threats to the soil


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World Geography 3202

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  • Deserts are shown in yellow. Threatened areas are in orange; the darker the color, the greater the threat.
  • Unit 3 lesson 5 threats to the soil

    1. 1. Threats to Soil
    2. 2. Threats to SoilEnvironmental or Natural Factors: Temperature Extremes - too hot or too cold! Affects humus accumulation (low temps.= slow the decay of organic matter). Too cold for any vegetation to grow = nothing to die, no humus. Ex. Tundra and Polar ice caps. Too hot = drought, with wind = dust storms or wind erosion. Ex. deserts Too cold = frozen ground, slow growth or short growing season. Again no humus! Ex. Tundra & Polar Ice Cap.
    3. 3. Threats to SoilEnvironmental or Natural Factors: Precipitation Extremes = too wet or too dry! affects mineral content (rain causes minerals to be eluviated or leached.) Washing away the soil or ground . (Erosion)… nutrients (leaching) Too dry = less vegetation growth = less accumulation of humus ex. Deserts Too wet = muddy, soaked soil = plants less able to obtain nutrients
    4. 4. Human – Threats to Soil pg. 140-143Poor Soil Management• Overusing the land …planting the same crop ALL the time.• Determine what land is BEST suited for and using it for that reason.• Ex. Don’t build on agricultural land. (urban expansion!)• Ex. Don’t grow grasses where land BEST suited for grapes.• Ex. Using chemical fertilizers and pesticides.• Ex. Leaving soil / land fallow. (NOT planting)
    5. 5. URBAN EXPANSION: Q. Is this the BEST use of this land? Q. What does this land seem MORE suitable for? Q. What other OPTIONS do they have? Threats to Soil pg. 140-143
    6. 6. Threats to Soil - Desertification• the spread of desert-like soil conditions in a semi-arid environment.• Turning productive soil into unproductive, dry, desert-like soil!• Occurs in hotter, drier areas and is accelerated by overgrazing, deforestation, leaving land fallow
    7. 7. Threats to Soil• Erosion • Flooding • Overgrazing • Deforestation
    8. 8. Reducing Soil Erosion Pg. 142Strip cropping Alternating strips of open-growing crops and close-growing crops. the close-growing crops act as a buffer or barrier to wind erosion. As well, the close-growing plants and roots prevent or hamper soil erosion (running water)
    9. 9. Reducing Soil Erosion Pg. 142 - Strip cropping
    10. 10. Reducing Soil Erosion Cover cropping • Planting close- growing crop when NOT planting a harvest crop. • Ground cover = shade = prevents soil from drying out, • Close growing plants prevent wind erosion• Roots prevent water erosion.• Soak up water preventing flooding• Increasing humus content = plants get ploughed back into the
    11. 11. Reducing Soil Erosion - Cover cropping
    12. 12. Reducing Soil ErosionContour ploughing• Respects the natural shape of the land.•Crops planted perpendicular to slope of land and water run-off.•Prevents soil erosion due to run-off.
    13. 13. Reducing Soil Erosion Terracing • Constructing steps or shelves in the sides of hills or sloping land to reduce water run-off and retain moisture.
    14. 14. Three Types of Soil Podzol : – soils which predominate the boreal forest and tend to be somewhat acidic Chernozem : – soils which tend to be the best for agriculture.  – are found in grasslands which are semi-arid resulting in less leeching and a mineral rich soil. Latosol : – soils which are very infertile due to the high amount of leeching.  – found in tropical rain forests with high