ch. 15 Soils

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ch. 15 Soils
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  1. Soil
    A dynamic natural material composed of both organic and mineral material that is essential for plant growth
  2. Soil Science
    the inter-disciplinary study of soils
  3. Pedology
    Study of the origin, classification, distribution, and description of soil
  4. Solum (soil profiles)
    surface and subsoil layers that have similar soil forming conditions
  5. Pedon (soil profile)
    basic unit in soil science that consist of a hexagonal soil column with a surface area between 1 and 10 m^2
  6. Polypedon
    combined pedons that is the basic soil unit used in soil mapping
  7. humus
    decayed plant and animal material that provides with additional nutrients and minerals
  8. Soil Moisture Storage
    the amount of water stored in soil and available for plants
  9. Hygroscopic Water
    Thin unavailable layer of water bound the soil particles
  10. Capillary Water
    held in soil by surface tension (available for use by plants)
  11. Gravitational water
    excess water that migrates downward to groundwater
  12. Field Capacity
    Maximum amount of water available for plants after gravitational water drains away
  13. Wilting Point
    Only hygroscopic water remains in soil which is unavailable for plant use
  14. Soil Moisture Utilization
    Plants must exert more energy to extract water as it nears the wilting point and unsatisfied demands represents a deficit (avoiding deficits an maximizing plant growth is the objective or irrigation)
  15. Soil Horizon
    • Each horizontal layer in a pedon
    • This has distinct characteristics differentiating it form layers above or below it.
  16. O Horizon
    Named for its high organic content and the presence of humus
  17. A horizon
    • Darker and richer in organic content than lower horizons¬†
    • Presence of humus and clay particles is important for providing a chemical link between soil nutrients and plants
  18. E horizon
    Consists of coarse sand, silt and resistant minerals.
  19. Eluviation
    • A and E horizon subject to this
    • clays and oxides of aluminum and iron are leached by percolating water and carried to lower horizons
  20. B Horizon
    • dominated by illuviation
    • may be reddish or yellow because of illuviated mineral or organic oxides
  21. Illuviation
    the process of accumulating clays, aluminum, and iron
  22. solum
    • combination of the A, E, and B soil horizons
    • this is where the most active soil development processes occur
  23. C Horizon
    • weathered bedrock
    • soil forming or biological processes have little influence in this horizon
  24. R Horizon
    unweathered bedrock
  25. Color
    Can suggest composition and chemical makeup of a soil, or dominant soil development processes
  26. Texture
    Size and organization of soil particles ranging from fine clays to course gravels (one of the most important diagnostic properties of soil)
  27. Structure
    Arrangement of soil particles
  28. Ped
    small natural cluster of soil particles
  29. Consistence
    Describes the cohesiveness of soils
  30. Porosity
    Ability of a soil to receive and drain water
  31. Acidity and Alkalinity
    • Optimum pH varies with plant species
    • Arid soils tend to be alkali while wetter soils are acidic
  32. Soil-forming regimes previously used to classify soils before the current soil taxonomy was created
  33. Laterization
    Leaching process in humid and warm climates (oxisols)
  34. Salinization
    Accumulation of salt in soils where climatic factors produce excessive evapotranspiration (Aridisols)
  35. Calcification
    The accumulation of calcium carbonates in continental climates (Mollisols, Aridisols)
  36. Podzolization
    Acidification of forest soils in cool climates (Spodosols)
  37. Gleization
    Accumulation of humus and a thick, underlying, water-saturated gray layer of clay in areas with a wet climate and poor drainage (Gleisols)
  38. U.S. Soil Taxonomy
    • A newer system of soil classification that recognizes both natural soil properties and changes that humans have introduced
    • Orders
    • Suborders
    • Great Goups
    • Subgroups
    • Families
    • Series
  39. Soil Orders
    Groupings of soils based on broadly similar composition, the presence or absence of specific diagnostic horizons, and similar degrees of horizontal development, weathering and leaching
  40. Diagnostic horizons
    include the epipedon (darkened by organic matter or leached of minerals) and the diagnostic subsurface horizon (located at varying depths)

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