1. Attributes of Soil Taxonomy

    • Quantitative definitions of taxa reduce subjectivity and clarify criteria
    • Taxa apply to real soil bodies as they occur rather than concepts
    • Based on soil properties that can be observed or measured rather than inferred
    • Can accomodate new knowledge
    • Should provide for all soils of the world and the landscape continuum

  2. Structure of the Taxonomic System

    • Hierarchical system of 6 categories

    Categories from highest to lowest levels of generalization

    ORDER 12
    SUBGROUP 1,400
    FAMILY 8,000
    SERIES 19,000

  3. Basic Concept of Each Taxonomic Category

    Category Nature of Criteria for Differentiating
    Order major soil forming processes ; diagnostic horizons
    Suborder genetic similarity; moisture regime, organic matter composition, parent material effects
    Great Group diagnostic layers, base status, horizon expression, clay activity
    Subgroup central concept of Great Group (Typic) or intergrades or extragrades
    Family properties important for soil use (texture, mineralogy,temperature)
    Series kind and arrangement of horizons, specific chemical mineralogical properties of horizons


    Order Formative Element Mnemonicon Derivation
    Histisol ist histology Gr. histos, tissue
    Spodosol od Podzol ; odd Gr. spodos,wood ashes
    Andisol and Ando Sp. Andes
    Oxisol ox oxide Fr. oxide
    Vertisol ert invert L. verto, turn
    Aridisol id arid L. aridos, dry
    Ultisol ult ultimate L. ultimus, last
    Mollisol oll mollify L. mollis, soft
    Alfisol alf Pedalfer
    Inceptisol ept inception L. inceptum, beginning
    Entisol ent recent
    Gelisol el gelifluction L. gelare, freeze

    1. Alfisols:
      Forest soils of cool moist climates, light colored, slightly to moderately acid with illuvial layer high in silicate clays.
    2. Andisols:
      Soils derived from volcanic materials.
    3. Aridisols:
      Arid soils common to western United States, often alkaline with salted horizons
    4. Entisols:
      Very young soils in new parent materials or where alluvial deposition or erosion limits profile development (slopes).
    5. Gelisols:
      Soils that commonly have a dark organic surface layer and mineral layers underlain by permafrost. These soils are commonly in the tundra regions of Alaska.
    6. Histosols:
      Organic Soils
    7. Inceptisols:
      Young soils, with only those horizons that form quickly.
    8. Mollisols:
      Prairie soils of the Great Plains. Dark, thick, good structure, high base A horizon.
    9. Oxisols:
      Highly weathered tropical soils. Has subsurface horizon low in weatherable minerals but high in aluminum or sesquioxide clays.
    10. Spodosols:
      Light colored acid forest, often coniferous, soils of cool humid regions as in northeast United States.
    11. Ultisols:
      Highly weathered soils of warm climates, low base, often leached, acid, and infertile.
    12. Vertisols
      High in swelling clays. When dry, large deep cracks form that surface soil falls into, mixing the soil.

    Cecil Series
    Official Description
    TAXONOMIC CLASS: Fine, kaolinitic, thermic Typic Kanhapludults
  5. Order: Ultisol

    Suborder: Udult

    Great Group: Kanhapludult

    Subgroup: Typic Kanhapludult

    Family: Fine, Kaolinitic, Thermic

    Series: Cecil