Soil

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Author:
katbaguisi
ID:
241188
Filename:
Soil
Updated:
2013-10-17 08:20:15
Tags:
soil
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Description:
for finals
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  1. What is soil?
    Solid earth material that has been altered by physical, chemical and organic processes so that it can support rooted plant life
  2. Why is soil important?
    • It is the growing medium for our food
    • Purifies our waste
    • Home to plants and animals
  3. How long can it take to form one inch of topsoil?
    100 years
  4. How much can an earthworm work for a year?
    A ton of soil
  5. What is soil made up of?
    • Mineral grains
    • 25% is air
    • Organic matter
    • Bacteria
  6. What are the factors of soil formation?
    • Climate
    • Organisms
    • Parental Material
    • Topography
    • Time
  7. How does climate help soil formation?
    The greater the rainfall amount, the more rapid the rate of both weathering and erosion
  8. How do organisms help soil formation?
    • Plant and animal activity produces humic acids that are powerful weathering agents
    • They stabilize soil profiles and tend to increase erosion
  9. How does parent material help soil formation?
    • Chemistry
    • Mineralogy
    • Grain size
  10. How does topography help soil formation?
    • Ground slope (the steeper the surface slope, the more likely any eroded material is to be transported out of the system)
    • - soils on hillslopes reach about 1m thickness while soils on flat surfaces, tend to thicken through time
    • Elevation
    • Aspect
  11. What does soil thickness mean?
    Reflects the balance between rates of soil production and rates of downslope soil movement
  12. How does time help soil formation?
    • Development and destruction of soil profiles
    • Typical reaction rates are slow, the longer a rock unit has been exposed, the more likely it is to be weathered
  13. What are the transformations of soil?
    • Decomposition of organic matter
    • Humification to form complex organic matter
    • Weathering of rocks
  14. What is decomposition?
    Breakdown of soil organic matter to form soluble compounds that can be absorbed or leached
  15. Primary layers of soil
    • Topsoil
    • Subsoil
    • Weathered bedrock
    • Bedrock
  16. What is on Ao horizon?
    Highly decayed organic material (Humus)
  17. What does humus do?
    Gives topsoil a rich brown color
  18. What happens in A horizon?
    Leaching
  19. What is leaching?
    Carries minerals down into the lower soil horizons
  20. What is on B-horizon or subsoil?
    Where the leached minerals end up
  21. Why do coastal plains have no bedrock?
    Instead it has layers of sand, clay and gravel because the sea level changes over time
  22. What is the best soil texture for growing things?
    • Loam -mixture of clay and silt
    • Contain a good supply of nutrients, necessary for the organisms living in the soil
  23. Grain sizes
    • Sandy particles - can be seen
    • Silt - feel powdery and don't hold together when went
    • Clayey - smallest soil particle
  24. Sieving soil fractions
    • Gravel
    • Sand
    • Silt
    • Clay
  25. What are the major nutrients found in fertile soils?
    • Nitrogen
    • Potassium
    • Phosphorus
  26. What helps maintain the balance of nutrients?
    Organic matter
  27. What is physical weathering?
    Breaks rocks into small mineral particles
  28. What is chemical weathering?
    Dissolves and changes mineral at the Earth's surface
  29. What is saprolite?
    Weathered rock that retains remnant rock structure
  30. What limits soil development?
    • Rapid erosion
    • Slow evolution
  31. What do landslides do?
    Redistribute and mix material creating uneven surfaces and topographic variability
  32. Methods to control soil erosion
    • Conservation tillage - crop residues are left in the ground
    • Crop rotation
    • Contour plowing - fields are plowed in curves
    • Strip cropping - placing closely sown crop under a loosely sown crop
    • Terracing - to catch downhill runoff
    • Shelter belt - to control blowing dust of the semiarid plains
    • Greenbelts - using shrubs and trees as boundaries

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