Classification of Soils

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Classification of Soils

• Introduction to Agriculture

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What will we learn today?

• How do we classify soils?
• What is a soil profile?
• What is a land capability class?
• What is the Soil Classification System?

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Soil Profile

• A soil profile is a cross-sectional view of a
  soil showing its many layers
• Each layer in the soil is called a horizon
• Shows many characteristics of each layer
• Thickness
• Color
• Texture
• Structure

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Soil Horizons

• A Horizon TOPSOIL
• 1 to 3 deep depending on region
• Rich in humus, soil organisms, plant roots
• B Horizon SUBSOIL
• Fine particles of clay, little organic matter
• Water drainage and root penetration
• C Horizon PARENT MATERIAL
• Not true soil, weathered parent material

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Other Horizons

• O Horizon - ORGANIC MATTER
• Plant or animal life
• Organic plant residues
• Decomposers
• R Horizon - BEDROCK
• 1 to 1,000

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Land Capability Class

• Land capability class is productive potential of
  soil based on
• texture, structure, slope and depth
• Class I best for agricultural production
• Class VIII least useful for agriculture

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Land Capability Class

• Class 1 Few limitations that restrict their
  use. Best for agriculture.
• Class 2 Moderate limitations that reduce the
  choice of plants or that require moderate
  conservation practices.
• Class 3 Severe limitations reducing choice of
  plants or requiring very careful management or
  both.
• Class 4 Very severe limitations reducing the
  choice of plants or requiring very careful
  management or both.
• Class 5 Not likely to erode but have other
  limitations, impractical to remove, that limit
  their use.
• Class 6 Severe limitations that making them
  generally unsuitable for cultivation.
• Class 7 Very severe limitations making them
  unavailable for cultivation.
• Class 8 Suitable only for wildlife, forests,
  and recreation.
• Subclasses indicate major limitations within a
  class. Class I has no subclasses.
• Subclass E Risk of erosion unless close-growing
  plant cover is maintained.
• Subclass W Water in or on the soil interferes
  with plant growth or cultivation
• Subclass S Shallow, droughty, or stone.

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Soil Classification System (SCS)

• Developed by USDA to categorize the different
  types of soils that exist
• All soils broken into 12 orders, then broken down
  further ending with series
• About 10,500 known in the United States alone
• Similar to binomial nomenclature used with
  plants, animals, etc.

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Soil Classification System (SCS)
Living Organisms Soils
Kingdom Order
Phylum Suborder
Class Great Group
Order Subgroup
Family Family
Genus Series
Species Phase
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What did we learn today?

• How do we classify soils?
• What is a soil profile?
• What is a land capability class?
• What is the Soil Classification System?