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  • 1. PA Soils
  • 2. Did you know…
    • It takes 550 years to make 1 inch of soil!
  • 3. What is soil?
    • The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for plant growth.
  • 4. What are the 4 main components of soil?
    • 1. Minerals
    • 2. Water
    • 3. Air
    • 4. Organic
    • matter
  • 5. What are soil horizons?
    • Soil horizons are distinct horizontal layers in the soil that have differing characteristics. Not all soils have all horizons
  • 6. The major soil horizons include…
    • O horizon
    • A horizon
    • E horizon
    • B horizon
    • C horizon
    • R horizon
  • 7. O Horizon
    • top, organic layer of soil (can still recognize leaves as leaves)
  • 8. A Horizon
    • Normally referred to as top soil.
    • This is where plant roots prefer to grow.
    • It is darker in color that the horizons below!
  • 9. E Horizon
    • Zone of eluviation
    • Clay is leached out of this layer so it is lighter in color than the A or B horizon.
    • There is not much of this in PA!
  • 10. B Horizon
    • Zone of accumulation
    • Where leached clay from E horizon accumulates
    • Thick and sticky with clay!
  • 11. C Horizon
    • Slightly broken up bedrock
    • Plant roots do not normally reach C horizon
  • 12. R Horizon
    • Unweathered rock
  • 13.  
  • 14.  
  • 15. 5 soil forming factors
    • 1. Parent material - material in which the soil forms.
    • 2. Climate - temperature and rainfall affect the amount of weathering. **Water is crucial for chemical weathering of bedrock.
    • 3. Biological Factors - plants and animals contribute to organic fraction of soil, and help breack down rocks and rock fragments.
    • 4. Topography - slope and aspect affect temperature of soil
    • 5. Time - soil formation is a continuous process affected by flooding, etc.
  • 16. Soil Texture
    • Soil texture is the percentage of sand, silt, and clay in a given soil.
  • 17. Soil Texture
  • 18. Soil particle sizes
    • Sand
    • .2 mm - .05mm
    • Silt
    • .05mm - .002mm
    • Clay
    • less than .002
  • 19. Why is soil texture important?
    • The texture of the soil affects many processes that occur within the soil such as infiltration rates and water holding capacity (WHC).
    • WHC - is how well the soil stores the water once it ets in there!
  • 20.
    • Sand: Largest particle size, fastest infiltration rates, lowest WHC
    • Silt: Medium particle size, medium infiltration rates, medium WHC
    • Clay: Smallest particle size, slowest infiltration rates, highest WHC
    • Infiltration - how fast the water enters the soils surface!
  • 21. What is soil structure?
    • Soil structure is the arrangement of soil particles into peds (peds = individual unit of soil structure).
    • Types of soil structure include: granular, platy, blocky, columnar, prismatic, and massive
  • 22.  
  • 23. Soil structures
    • Granular - common in A horizon - best structure for roots to grow in.
  • 24.
    • Platy - found in B horizon and in compacted soils. Really bad for plant roots!
  • 25. Blocky soil structure
    • Blocky - Found in subsurface horizons
    • Below the A horizon
  • 26. Columnar soil structure
    • Columnar - vertical columns of soil that have a salt “cap” at the top. Found in arid climates.
  • 27. Prismatic soil structure
    • Prismatic - vertical columns of soil, usually found in subsurface horizons.
  • 28. Massive soil structures
    • Massive - Soil with no visible structure, very large clods.
  • 29. What is soil organic matter (SOM)?
    • Plants and animals in
    • various stages of
    • decomposition.
  • 30.
    • SOM increases water holding capacity, infiltration rates, improves compaction, binds harmful pesticides and heavy metals, and provides energy for soil microbes.
    • Tilage decreases SOM content in the soil because it increases the decomposition rates.
  • 31. What is CEC?
    • Common cations (positively charged ions) found in soil: silicon, aluminum, iron, magnesium, calcium, sodium, potassium
    • Common anion (negatively charged ions) in soil: oxygen
  • 32.
    • Soil pH is an indication of the acidity or alkalinity of the soil.
    • Acid pH =0 - 7
    • Neutral pH =7
    • Alkaline (basic) pH = 7 - 14
    • Most plants prefer to grow where the soil pH is around 6 - 7.
    • If soil pH is too low, lime can be added to raise the soil pH
  • 33. Soil erosion
    • The loss of soil from the landscape. Caused by:
      • Water: sheet, rill and gully
      • Wind: Dust bowl
      • Man/mechanical: construction sites
  • 34. Sheet
    • Removal of a uniform thin layer of soil by raindrop splash or water run-off
  • 35. Rill
    • Removal of soil by concentrated water running through little streamlets
  • 36. Gully
    • Severe erosion in which trenches are cut to a depth greater than 1 foot.
  • 37. Dust Bowl
    • The natural deep-roooted grasses that normally kept the soil in place and trapped moisture even during periods of drought and high winds was removed.
    • During the drought of the 1930s, without natural anchors to keep the soil in place, it dried, turned to dust, and blew away eastward and southward in large dark clouds.
  • 38. Conservation practices
    • Riparian buffers - planting of trees/shrubs along streambanks to filter or stabilize soil and reduce soil erosion
  • 39.
    • Filter Strips - Strips of grass used to trap sediment and chemicals before reaching a body of water.
    • Grassed waterways - strips of grass in areas where water concentrates or flows off of a field.
  • 40.
    • Contour Farming plowing across the slope and with the contour of the field.
  • 41. Soil compaction
    • When soil particles are pressed together, reducing the pore space between them
    • Soil compaction is caused by wheel traffic and tilling soil.
    • Soil compaction reduces water infiltration and plant growth!