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SW85

Australian Soil Classification: Vertic (& Calcic), Subnatric, Grey SODOSOLGeneral Landscape Description: Gently undulating plain
Site Description: Alluvial Plain, flatGeology: alluvium in basalt plain (Qrm)


Soil Profile Morphology:


Surface Soil


Ap0-10 cmVery dark greyish brown (10YR3/2 moist); fine sandy clay loam, pH 5.7:
South West Gasp Pipeline GP85 Profile
SW85 Profile
A210-25 cmVery dark greyish brown (10YR3/2 moist), conspicuously bleached (10YR6/2 dry); fine sandy clay loam; rusty root channels; pH 5.9; abrupt change to:
Subsoil
B21t 25-65 cmDark grey (10YR4/1 moist); heavy clay; coarse [15-40 cm], coarse prismatic, parting to irregular moderate blocky structure; mixed rough and smooth faced peds; strong consistence; pH 7.4; gradual change to:
B22ss65-100 cmLight olive brown (2.5Y5/3 moist) to greyish brown (2.5Y5/2 moist); strongly vertic; slickensides [10-20 cm]; pH 9.0; gradual change to:
B23ss100-130 cmLight olive brown (2.5Y5/4 moist); light medium clay; coarse lenticular, parting to fine lenticular structure; very large slickensides; pH 9.1; sharp change to:
B24k130 cm+Light brownish grey (2.5Y6/2 moist); brownish yellow (10YR6/8 moist) mottles; soft carbonate and hard silica rich calcium carbonate nodules; pH 9.3:

Key Profile Features:
  • Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
  • Vertic properties in deeper subsoil (i.e. slickensides and lenticular peds).

Soil Profile Characteristics:

pH
Salinity Rating
Sodicity
Dispersion
Surface
(A1 horizon)
Moderately Acid
Very Low
Non-Sodic
None1
Subsoil
(B21 horizon)
Slightly Alkaline
Low
Sodic
Complete
Deeper subsoil
(at 130+ cm)
Very Strongly Alkaline
Medium
Strongly Sodic
-
1 moderate dispersion after remoulding

South West Gasp Pipeline GP85 Graphs

Horizon
Horizon Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
1:5
NaCl
%
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-10
5.7
4.7
0.1
5
2.8
4.8
0.34
0.77
A2
10-25
5.9
4.7
0.09
2.2
4.6
0.24
0.9
B21
25-65
7.4
6.2
0.18
4.4
14
0.72
3.3
B22
65-100
9
8.4
0.86
0.11
5.7
19
0.6
8.6
B23
100-130
9.1
8.5
0.85
0.11
B24
130+
9.3
8.5
0.77
0.1

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
13
10
28.4
11.1
21.4
35.1
15
20.5
A2
10-25
13
10
26.1
9.6
17.2
40.2
19
19
B21
25-65
<10
8.8
35.7
16.4
16
32.6
15.5
30.5
B22
65-100
55.8
26.7
7.2
17.7
13
55.5
B23
100-130
B24
130+


Management Considerations:

Subsoil (B) Horizons

  • The dense and coarsely structured subsoil is sodic and disperses completely. This will result in significantly restricted root and water movement into the subsoil.
  • 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.


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