Physical Properties

Physical Properties

Physical Properties
Textural Properties
Separate
Properties

Soil Texture
Classes

Soil
Structure
Pans
Density & Pore Space
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Soils
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I. Particle size classification

        defines surface area

        pore space properties

2. Engineering classification    -      phi sizes    =    -log₂ (diameter in mm)

        -1 phi = 2mm                    - sand
       0 phi = 1mm
         1 phi = 0.5mm
         2 phi = 0.25mm
         3 phi = 0.125mm

         4 phi = 0.0625mm           ~ silt
         5 phi = 0.0312
         6 phi = 0.0156
         7 phi = 0.0078
         8 phi = 0.004

       9 phi = 0.002                   ~ clay

3. USDA System    -   (used by soil scientists)

   Coarse Fragments -    (by sieve)

            Boulders     >60 cm
            Stones          25-60 cm
            Cobbles        7.5-25 cm
            Gravels         0.2 - 7.5 cm

   Soil Separates    -    (by feel or Buoyocos hydrometer)

            Sands          0.05 - 2.0 mm

                    very coarse
                    coarse
                    medium
                    fine
                    very fine

            Silt              0.002 - 0.05

            Clay              <0.002              - colloid, roughly the size of a bacterium

Desirable texture     -    at least 10% each of sand, silt and clay
                                     few coarse fragments

Glacial Outwash     -   typically has over 95% sand.

Glacial Tills             -   have only slightly more silt and clay