1. Physical Properties of Soils GES175, Science 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 Silt Sand Loamy Sand Sandy Loam Sandy Clay Loam Silt Loam Loam Clay Loam Silty Clay Loam Silty Clay Percent Silt Percent Clay Percent Sand 40 60 75 90 55 35 20 10 Sandy Clay 70 50 20

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

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

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

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

8. + Flocculation Creating Structure (chemical)

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

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

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

12. Spheriodal Granular Soil Structure: Surface Horizons

13. Poor Management Granular Massive

14. Compaction of Surface Horizons - Platy Structure - compaction

15. Impact on soil compaction ?

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

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

18. Organic soil D b  0.8 Mg/m 3 Bulk Densities

19. Compacted Subsoil è D b  1.7 Mg/m 3 Bulk Densities Organic soil D b  0.8 Mg/m 3 versus

20. Well Sorted Sand Macroporosity Clay Aggregates

21. + Flocculation Aggregation Internal Porosity Micropores

22. Volcanic Ash Soil Timber Harvest