SW83
| Australian Soil Classification: Vertic (& Calcic), Subnatric, Black SODOSOL | General Landscape Description: Gently undulating basalt plain |
Soil Profile Morphology:
Surface Soil
| A1 | 0-10 cm | Very dark brown (10YR2/2 moist), dark greyish brown (10YR4/2 dry); loam; pH 5.5; clear change to: |  SW83 Profile - Note: Surface (A1) horizon has been stripped from the profile |
| A2 | 10-60 cm | Dark greyish brown (10YR4/2 moist), conspicuously bleached; (10YR7/2 dry); sandy clay loam; apedal; massive; few (2%), fine buckshot nodules (concentrated in pockets); pH 6.6; abrupt and wavy change to: | |
| Subsoil |  | | |
| B21 | 60-90 cm | Black (10YR2/1 moist); heavy clay; few pockets of ferruginous fine gravel; coarse prismatic structure; pH 6.8; abrupt change to: | |
| B22 | 90 cm+ | Mottled dark geyish brown grey with (10YR6/1 moist) and minor (<2%), brownish yellow (10YR6/8 moist) and light olive brown (2.5Y5/4 moist) mottles, soft calcareous segregations; strongly vertic; medium clay; medium prismatic structure; pH 8.6. |
Key Profile Features:
- Strong texture contrast between surface (A) horizons and subsoil (B) horizons.
- Variable depth of A horizons due to gilgai microrelief.
Soil Profile Characteristics:
| pH | Salinity Rating | Sodicity | Dispersion |
Surface (A1 horizon) | Strongly Acid | Low | Non-Sodic | None |
Subsoil (B21 horizon) | Slight Acid | Low | Sodic | None1 |
Deeper subsoil (at 90+ cm) | Strongly Alkaline | Low | Strongly Sodic | Strong - Complete |
| 1 complete dispersion after remoulding | ||||
 |
Horizon | Horizon Depth (cm) | pH (water) | pH (CaCl2) | EC 1:5 | NaCl % | Exchangeable Cations | |||
Ca | Mg | K | Na | ||||||
meq/100g | |||||||||
A1 | 0-10 | 5.5 | 4.9 | 0.21 | | 6.2 | 3.2 | 0.61 | 0.37 |
A2 | 10-60 | 6.6 | 6 | 0.06 | | 1.7 | 1.4 | <0.05 | 0.18 |
B21 | 60-90 | 6.8 | 5.6 | 0.11 | | 5.9 | 11 | 0.3 | 2.4 |
B22 | 90+ | 8.6 | 7.5 | 0.25 | | 7 | 12 | 0.28 | 4 |
Horizon | Horizon Depth (cm) | Ex Al mg/kg | Ex Ac meq/100g | Field pF2.5 | Wilting Point pF4.2 | Coarse Sand (0.2- 2.0 mm) | Fine Sand (0.02- 0.2 mm) | Silt (0.002- 0.02 mm) | Clay (<0.002 mm) |
A1 | 0-10 | <10 | 12 | 25.6 | 10.8 | 22.9 | 37 | 13.5 | 20.5 |
A2 | 10-60 | | 3.3 | 16.6 | 3.8 | 28.6 | 46.2 | 14 | 11.5 |
B21 | 60-90 | | 11 | 39.4 | 22.4 | 14.4 | 21.4 | 7 | 54.5 |
B22 | 90+ | | | 39.3 | 19.9 | 15.3 | 28.4 | 7.5 | 46.5 |
Management Considerations:
Subsoil (B) Horizons
- This profile is the “hollow” of a gilgai soil. See GP 82 for description of the associated “puff”.
- The subsoil displays vertic features (i.e. slickensides) which indicates that significant shrinking and swelling occurs during wetting and drying cycles. This may have engineering implications and is likely to explain the variability in surface horizon depth across the trench.
Notes
- Very variable between puffs and hollows. Intermittent/discontinuous cycle is every 2 - 3 m.
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