Soils

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Soils
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Terms and Definitions

• Soil- outermost layer capable of supporting plant
  growth
• Organic matter- decomposed plant and animal
  material
• Minerals- inorganic elements
• Nitrogen, potash, phosphorus

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Terms and Definitions

• Soil profile- cross section of a soil from top to
  bottom
• Soil texture- size of the individual soil
  particles
• Soil color- indication of the amount of organic
  matter, moisture, texture

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Terms and Definitions

• Soil structure- way in which individual soil
  particles are grouped together
• Rock weathering- process by which rocks are
  broken down
• Leaching- removal of soil comp0onents by the
  downward action of water
• Rock- consolidated mass of two or more minerals

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Terms and Definitions

• Aggregate- single mass or cluster of soil such as
  clod, crumbs, or granules
• Slope- number of feet fall in each 100 ft of
  distance
• Permeability- Movement of air and water through
  the soil
• Depth- total thickness of soil from the topsoil
  to the parent material

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Importance of soils

• Provide food
• Provide energy
• Provide shelter

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Factors affecting soil formation

• Parent materials
• Rocks
• Igneous
• Metamorphic
• Moved by
• Wind
• Water
• Glaciers

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Factors affecting soil formation

• Weathering
• Physical
• Chemical
• Climate
• Temperature
• Rainfall

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Factors affecting soil formation

• Vegetation and organisms
• Plant
• Animal
• Slope and drainage
• Hillsides
• Thin topsoil caused by erosion
• Less plant growth, organic matter, leaching
• Flat lands
• Deeper topsoil
• More vegetation, organic matter, leaching

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Benefits of organic matter

• Makes soils porous
• Supplies nitrogen to the plant
• Holds water in the soil
• Furnishes food for soil organisms
• Stores mineral nutrients
• Reduces leaching
• Stabilizes soil structure

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Soil Particles

• Sand
• Silt
• Clay

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Soil Profile

• Topsoil
• Subsoil
• Parent material

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Kinds of soil structures

• Crumb- very porous granular structure
• Granular- grains grouped into spherical
  aggregates
• Platy- thin vertical axis and long horizontal
  axis
• Prismatic- prismlike aggregate
• Blocky- aggregate has equal sides
• Columnar- columnlike structure

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Soil Color

• Dark brown or black- higher in organic matter
• Red- high iron content
• Yellow- imperfect drainage
• Gray- low in organic material

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Composition of an average soil

• Mineral matter- 48
• Water- 25
• Air- 25
• Organic matter- 2

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Degrees of erosion

• None to slight- lt25
• Moderate- 25 to 75
• Severe- 75
• Very severe- gt75

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Soil depths

• Deep- gt36 inches
• Moderately deep- 20 to 36 inches
• Shallow- 10 to 20 inches
• Very shallow- lt10 inches

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Degrees of permeability

• Very slow- dense, heavy clay or claypan soils
• Slow- crumbly, clayey subsoils
• Moderate- have high granular, clay loam subsoils
• Rapid- sandy subsoils

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Degrees of slope

• Nearly level- lt1 slope
• Gently sloping- 1to 3
• Moderately sloping- 3 to 5
• Strongly sloping- 5 to 8
• Steep- 8 to 12
• Very steep- gt12