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SW82

Location: Warncoort

Australian Soil Classification: Vertic (& Sodic), Calcic, Black CHROMOSOL


General Landscape Description: Gently undulating plain.
Site Description: Puff of a gilgai.
Geology: Basalt plain.


Soil Profile Morphology:


Surface Soil


A10-10 cmVery dark brown (10YR2/2 moist); loam; pH 5.5; clear change to:
South West Gasp Pipeline SW82 Profile
SW82 Profile. Note: Surface (A1) horizon has been stripped from the soil profile
Subsoil

B2110-40 cmVery dark grayish brown (10YR3/2 moist); medium heavy clay; medium to fine (5-20 mm) polyhedral structure; strong consistence dry; pH 5.8; gradual change to:
B2240-90 cmDark grayish brown (10YR4/2 moist) and brownish yellow (10YR6/6) mottles; heavy clay; some pockets of fine buckshot; coarse prismatic, parting to fine lenticular structure; strong consistence dry; pH 6.8; abrupt change to:
B23ssgk90 cm+Dark grayish brown (10YR4/2 moist) with brownish yellow (10YR6/6 moist) and very few (<2%) light olive brown (2.5Y5/4 moist) mottles ; medium (20-50 mm) prismatic structure; strong consistence dry; very few (<2%) soft carbonate segregations; strongly vertic; pH 8.5.


South West Gasp Pipeline SW82 Profile 2
SW82 Profile wider view.


Key Profile Features:
  • Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
  • Colour contrast in deeper subsoil.

Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Strongly Acid
Low
Non-Sodic
None
Subsoil
(B21 horizon)
Moderately Acid
Very Low
Non-Sodic
None1
Deeper Subsoil
(at 90+ cm)
Moderately Alkaline
Low
Strongly Sodic
Strong - Complete
1 Slight dispersion after remoulding.
Image: SW82 Graphs
The surface soil is strongly acid. The subsoil is moderately acid becoming moderately alkaline with depth.Salinity rating is low in the surface becoming very low in the subsoil.
    The soil is non sodic in the surface and upper subsoil and strongly sodic in the deeper subsoil.
The clay content increases markedly at the A/B boundary.

Horizon
Sample 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
B21
10-40
5.8
4.8
0.1
<0.01
7.2
7.9
0.4
0.5
B22
40-90
6.8
5.6
0.09
7.9
13
0.41
1.8
B23
90+
8.5
7.3
0.17
6.5
12
0.27
3.2

Horizon
Sample Depth
(cm)
Exchangeable Aluminium
mg/kg
Exchangeable Acidity
meq/100g
Organic Carbon
%
Nitrogen
%
Field
Capacity
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
3.8
0.29
25.6
10.8
23
37
14
21
B21
10-40
18
15
39.6
24.6
13
21
7
56
B22
40-90
12
45.5
26.7
11
16
6
63
B23
90+
18
25
7
48


Management Considerations:

Subsoil (B) Horizons

  • This profile is the “puff” of a gilgai soil. See GP 83 for a description of the associated “hollow”.
  • 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
  • Between Aireys Reserve Rd and Birregurra Creek soil has coarse prismatic subsoil, very gilgaied, some patches of soft calcium carbonate (CaCO3) below 1 m. Abrupt A2/B boundary. Deeper material grey/yellow mottled clay with fine quartz gravel >10 mm, rounded, below 1.5 m (<5% of matrix). Some (occasional) fragments of ferrguniated sandstone (<50 mm) in subsoil, but rare.

Profile Described By: Richard McEwan (March 1999).

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