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SW67

Location: Irrewillipe

Australian Soil Classification: Bleached-Mottled (& Reticulate), Eutrophic, Brown CHROMOSOL

General Landscape Description: Weakly dissected coastal plain, gently inclined undulating plain.
Site Description: Gently sloping above broad plain.
Geology: Hanson Plain Sand

Image: SW6& Landscape
SW67 Landscape


Soil Profile Morphology:


Surface Soil


A10-10 cmVery dark gray (7.5YR3/1 moist), dark grayish brown (10YR4/2 dry); fine sandy loam; weakly pedal; weak consistence; pH 5.2; clear and irregular change to:
South West Gasp Pipeline SW67 Profile
SW67 Profile

Note: Surface (A1) horizon has been stripped from profile

A2

40-50/60 cm

Brown (10YR4/3 moist), yellowish brown (10YR5/4 dry) in upper part of horizon, tending to olive brown (2.5Y4/4 moist), light olive brown (2.5Y5/6 dry); fine sandy clay loam; occasional buckshot gravel in lower part of horizon and some manganiferous mottles or soft concretions; faint rusty mottles (~5 mm); weak consistence; pH 5.8; clear and wavy change to:

Subsoil

B21t56/60-90/95 cmDark yellowish brown (10YR3/4 moist); with faint yellow and brown mottles; gravelly clay loam; fine polyhedral structure; firm consistence; friable in moist state; few (5-10%) fine to coarse rounded ironstone buckshot nodules (2-20 mm); pH 6; gradual change to:

B22tg

90-95-120 cm

Dark grayish brown (10YR4/2 moist); with many (30-50%), yellowish brown (10YR5/8 moist) mottles; thick, dark brown (10YR3/3 moist) cutans; yellow, dull red and black ped interiors; manganese coatings on some ped faces and soft accumulations inside peds; diffuse change to:

B23g

120-210/300 cm

Dark brown (10YR3/3 moist); common (<20%), yellowish brown (10YR5/8 moist) mottles with soft and hard manganiferous concretions (~20 mm) (5-10%); broad tongueing [300 mm] into B/C horizon; pH 6.3; clear to abrupt boundary and tongueing into:

B/C

210/300+ cm

Conspicuous reticulate laminar mottling:"Tiger Mottles" red (10R4/6) and gray (2.5Y6/1). Lamellae 10-20 mm apart:a red matrix is rigid strongly cemented ferruginised sand, gray lamellae are soft sandy to clay. Margins of lamellae are often yellow (10YR7/8) to yellowish brown (10YR5/8). Red matrix frequently presents as angular ironstone gravel (10-20 mm).


South West Gasp Pipeline SW67 Tiger Mottles
Tiger Mottles at 210 cm depth.


Key Profile Features:
  • Conspicuously bleached subsurface (A2) horizon.
  • Strong texture contrast between surface (A) horizon and subsoil (B2) horizon.
  • “Tiger mottling” in deep subsoil (i.e. below 2 m depth).

Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Strongly Acid
Very Low
Non-Sodic
None
Subsoil
(B21 horizon)
Moderately Acid
Very Low
Non-Sodic
None
Deeper Subsoil
(at 120-140 cm)
Slightly Acid
Very Low
Non-Sodic
None


Image: SW67 Graphs

The surface is strongly acid. The subsoil is moderately acid becoming slightly acid with depth. Salinity rating is very low throughout the profile.The soil is non sodic throughout.Exchangeable Aluminium levels are high in the surface soil.Clay levels jump markedly at the surface / subsoil boundary.

Horizon
Sampling Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
1:5
Organic Carbon
%
Nitrogen
%
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-10
5.2
4.4
0.09
3.6
0.26
2.1
0.86
0.11
0.22
A2
40-50
5.8
4.8
<0.05
2.1
0.88
<0.05
0.08
B21
70-85
6
5.2
0.06
2.8
7.3
0.12
0.45
B23
120-140
6.3
5.4
0.06

Horizon
Sampling Depth
(cm)
Exchangeable Aluminium
mg/kg
Exchangeable Acidity
meq/100g
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
130
17
23.7
9
8.8
53.6
13
18
A2
40-50
18
6.9
20.3
7
11.5
54.7
12.5
18.5
B21
70-85
<10
12
37.4
25.4
3.5
21
7
67
B23
120-140

Profile Described By: Richard McEwan (March 1999).
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