Soil Physical Properties
14 | Unit 2.1
iv. Size: very fine, fine, medium, coarse, very coarse, thick, thin
v. Grade
Weak: Peds barely observable in place, difficult to distinguish from massive or single grain.
Moderate: Peds well formed and evident in undisturbed soil
Strong: Peds distinct in undisturbed soil. Peds have distinctive surface features.
vi. Compound structure
• One structure beside another
• One structure within another (“parts to...”)
vii. Persistence upon wetting and drying—“Aggregate stability”
tabLe 5. SIzE CLASSES OF SOIL STRUCTURAL UNITS. THIN ANd THICk, RATHER THAN FINE ANd COARSE, ARE USEd FOR PLATy
STRUcTURES.
size cLass pLaty cOLUMnar/ bLOcKy granULar
prisMatic
very fine (thin) <1 mm <10 mm <5 mm <1 mm
fine (thin) 1 – 2 mm 10 – 20 mm 5 –10 mm 1 – 2 mm
medium 2 – 5 mm 20 – 50 mm 10 – 20 mm 2 – 5 mm
coarse (thick) 5 –10 mm 50 –100 mm 20 –50 mm 5 –10 mm
very coarse (thick) >10 mm >100 mm >50 mm >10 mm
Students’ Lecture OutlinefigUre 3. SOIL TExTURE TRIAnGLE