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SW39

Location: Irrewillipe.

Australian Soil Classification: Melacic (& Vertic), Eutrophic, Black DERMOSOL

Map Unit: Map Unit 116 (Maher and Martin, 1987).

General Landscape Description: Level plain (possibly a terrace).
Site Description: Grazing paddock (dairy).
Geology: Quaternary sediments overlying Tertiary - Moorabool Viaduct Formation.

SW39 Landscape
SW39 Landscape


Soil Profile Morphology:

Surface Soil

A10-25 cmVery dark brown (10YR2/2); very fine sandy clay loam; weak coarse blocky, parting to moderate coarse blocky structure; firm consistence moist; pH 5.4:
SW39 Profile
SW39 Profile
A2125-40 cmVery dark greyish brown (10YR3/2), sporadically bleached; very fine sandy clay loam; weak coarse blocky structure; weak consistence moist; pH 5.7:
A2240-65 cmDark greyish brown (10YR4/2) with brownish yellow (10YR6/6) mottles, sporadically bleached; fine sandy clay loam (heavy); weakly structured; weak consistence moist; pH 5.6:
Subsoil
B2165-90 cmVery dark brown (10YR2/2); light clay (fine sandy); moderate coarse blocky structure; firm consistence moist; pH 5.6:
B2290+ cmVery dark brown (10YR2/2) with a few yellowish brown (10YR5/8) mottles; medium clay; strong medium lenticular, parting to strong very fine lenticular structure; firm consistence moist; pH 5.7.

Key Profile Features:
    Very high salinity in the surface soil.

Soil Profile Characteristics:



pH



Salinity Rating
Surface
(A1 horizon)
Strongly Acid
Very High- Extremely High
Non-Sodic
None
Subsoil
(B21 horizon)
Moderately Acid
High
Marginally Sodic
Slight
Deeper Subsoil
(at 90+ cm)
Moderately Acid
Moderate-High
Marginally Sodic
None

Graph: SW39 pH

The surface horizon is strongly acid. The subsoil is moderately acid.
Graph: SW39 Salinity
The salinity rating is very high to extremely high
at the surface. The subsoil is high becoming
moderate to high with depth.
Graph: SW39 Clay

The clay content increases gradually with depth.


Horizon
Horizon Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
(dS/m)
NaCl
%
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-25
5.4
4.9
0.81
0.18
4
1.5
0.2
0.4
A21
25-40
5.7
5.1
0.71
0.016
2.4
1.3
0.2
0.4
A22
40-65
5.6
5
0.64
0.015
2.5
1.2
<0.1
0.4
B21
65-90
5.6
5.1
0.7
0.16
3.2
3.8
<0.1
1
B22
90+
5.7
5.2
0.77
0.09
2.3
4.4
<0.1
1.1

Horizon
Horizon Depth
(cm)
Acidity
meq/100g
Oxidisable Organic Carbon
%
Total
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
0-25
3.7
0.23
30
9.7
9
50
20
15
A21
25-40
24.9
5.4
8
54
23
14
A22
40-65
22.3
5.4
9
55
16
21
B21
65-90
7.1
31.9
14.4
6
40
18
37
B22
90+
33.1
15.9
5
37
18
41

Management Considerations:

  • Friable surface soils (and subsoils) occur where there is a build up of organic matter, (and to some extent iron rich clay complexes) generally in cooler wetter areas (less extreme wetting and drying cycling).
  • Bleached A2 horizons (or subsurface soils) are a major feature of many of soils within the Corangamite CMA region. They are an indication of restricted drainage, poor soil structure (often massive) and low organic matter, nutrient and water holding capacity, nearly always in conjunction with a restrictive soil below such as a clayey soil or a pan (eg. coffee rock). These bleached horizons may act as conduit for subsurface flow, particularly on sloping ground. If the soil is dispersive then gypsum application would be suitable, while increasing organic matter and maintaining vegetative cover is important.

Profile Described By:
Mark Imhof and Austin Brown (June 1998).
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