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Physical Properties of Soils

GES175, Science of Soils. Physical Properties of Soils. Particle Size. * Physical properties are influenced by particle size Size Classification (USDA): Soil < 2 mm Sand, 2 - 0.05 mm Silt, 0.05 - 0.002 mm Clay, <0.002 mm . Textural Triangle. Clay. Percent Silt. 40.

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Physical Properties of Soils

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  1. GES175, Science of Soils Physical Properties of Soils

  2. Particle Size * Physical properties are influenced by particle size Size Classification (USDA): Soil < 2 mm Sand, 2 - 0.05 mm Silt, 0.05 - 0.002 mm Clay, <0.002 mm

  3. Textural Triangle Clay Percent Silt 40 Percent Clay 55 Silty Clay Sandy Clay 60 35 Silty Clay Loam Clay Loam Sandy Clay Loam 75 20 Loam Silt Loam Sandy Loam 90 10 Loamy Sand Silt Sand 50 70 20 Percent Sand

  4. Clay 40 55 Silty Clay Sandy Clay 60 Silty Clay Loam Clay Loam Clayey Soil (fine textured)

  5. 60 35 Silty Clay Loam Sandy Clay Loam 75 20 Loam Silt Loam 90 Silt 50 70 20 Loamy/Silty Soils (medium textured)

  6. 20 Sandy Loam 10 Loamy Sand Sand 50 70 Sandy Soils (coarse textured)

  7. Soil Structure granular Cause and Effect (description in laboratory) prismatic

  8. + Creating Structure Flocculation (chemical)

  9. Surface Area vs - large grain - aggregate of small particles

  10. Creating Structure - organic and inorganic ‘glues’ Aggregation

  11. Stress Forces (what breaks the ‘glue’) Vertical Lateral

  12. Soil Structure: Surface Horizons Spheriodal Granular

  13. Massive Poor Management Granular

  14. Compaction of Surface Horizons compaction - Platy Structure -

  15. Impact on soil compaction?

  16. Structure: Subsurface ---- Prizmatic ---- Increased length in vertical direction - lateral stress > vertical stress

  17. Blocky Structure: (subsurface horizons) • Increased (relative) age equates stress fractures

  18. Bulk Densities Organic soil Db» 0.8 Mg/m3

  19. Bulk Densities Organic soil Db» 0.8 Mg/m3 versus Compacted Subsoil è Db» 1.7 Mg/m3

  20. Macroporosity Clay Aggregates Well Sorted Sand

  21. + Flocculation Aggregation Internal Porosity Micropores

  22. Timber Harvest Volcanic Ash Soil

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