Soil Texture and Structure

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Soil Texture and Structure
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Soil Texture

• Mineral material only
• Material gt 2mm are coarse fragments
• Material lt 2mm only
• Sand - 2.0 - 0.05 mm
• Silt - 0.05 - 0.002 mm
• Clay - lt 0.002 mm

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Soil Texture (mineral material only)

• Sand - gritty
• Silt - smooth, velvety
• Clay - slick, sticky

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USDA Textural Classes (12)

• Sand
• Loamy Sand
• Sandy Loam
• Loam
• Silt Loam
• Silt

• Sandy Clay Loam
• Silty Clay Loam
• Clay Loam
• Sandy Clay
• Silty Clay
• Clay

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Examples
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Sand Silt Clay 100
40 Sand40 Silt20 Clay
Texture LOAM
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25 Sand?? Silt45 Clay
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25 Sand30 Silt45 Clay
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25 Sand30 Silt45 Clay
CLAY
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65 Sand20 Silt?? Clay
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65 Sand20 Silt15 Clay
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65 Sand20 Silt15 Clay
SANDY LOAM
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?? Sand30 Silt30 Clay
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40 Sand30 Silt30 Clay
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40 Sand30 Silt30 Clay
CLAY LOAM
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Field Determination of Texture
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Field determination of texture

• Soil must be moist, not saturated moist enough
  to mold like putty when you try to form a ball in
  your hand.
• Soil Texture Class Key
• Does soil form a ball or cast?
• No - the texture is SAND

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Soil does not form a cast Textural class is SAND
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Field determination of texture

• Can the ball be handled
• No - the texture is LOAMY SAND.
• OR
• When pressing the soil between thumb and
  forefinger does the soil form a ribbon that
  extends beyond your forefinger?
• No - the texture is LOAMY SAND.

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Forms a cast of moist soil material. Textural
class is LOAMY SAND
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Making a ribbon
The length of the ribbon will depend on
mineralogy as well as clay content
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Field determination of texture

• If the soil forms a ribbon that that extends past
  the forefinger, note the length of the ribbon.
• Next excessively wet a small sample in the palm
  and rub with the forefinger.

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Field determination of texture

• If the ribbon was lt 1 inch long when it broke and
  the excessively wet sample feels
• gritty, the texture is SANDY LOAM
• smooth, the texture is SILT LOAM
• neither gritty nor smooth, the texture is LOAM.

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Field determination of texture

• If the ribbon was between 1 and 2 inches long
  when it broke and the excessively wet sample
  feels
• gritty, the texture is SANDY CLAY LOAM smooth,
• the texture is SILTY CLAY LOAM
• neither gritty nor smooth, the texture is CLAY
  LOAM.

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Field determination of texture

• If the ribbon gt 2 inches long when it broke and
  the excessively wet sample feels
• gritty, the texture is SANDY CLAY
• smooth, the texture is SILTY CLAY
• neither gritty nor smooth, the texture is CLAY.

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Soil Structure
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Examples
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Strong, coarse columnar
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Moderate, very coarse, prismatic
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Moderate/strong, thick platy
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Moderate, coarse granular Moderate to strong,
medium prismatic parting to moderate to strong,
medium subangular blocky
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Weak, medium subangular blocky
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Moderate, coarse prismatic parting to weak to
moderate, medium to coarse subangular blocky
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• Texture Plays a Major Role with Micropores.
• Structure Plays a Major Role with Macropores.