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PPW5

Location: Werribee - Research Farm
Aust. Soil Class.: Calcic, Subnatric, Red SODOSOL (medium to thick surface horizons)
Northcote Factual Key: Dr 2.13
Great Soil Group: red-brown earth
Previous Soil Type (Skene 1954): Werribee loam
Maher and Martin (1979) map unit: 10b
General Landscape Description: Level plain (with prior streams).
Site Description: Grazing paddock. This site is probably associated with a levee of a prior stream.
Geology: Quaternary alluvial (prior stream) and aeolian deposits.

Photos Werribee WP2landscape
WP2 Landscape

Soil Profile Morphology


Surface Soil






Photos Werribee WP2 profile
PPW5 Profile



A1

0-10 cm

Brown (7.5YR4/4),
fine sandy clay loam; weak coarse, parting to moderate medium blocky structure; strong consistence (dry); compacted in upper 3 cm; pH 5.6; sharp change to:

A12

10-20 cm

Strong brown (7.5YR4/6);
heavy fine sandy clay loam; moderate coarse blocky, parting to strong medium polyhedral structure; strong consistence (dry); pH 6.0; clear change to:

Subsoil

B21

20-55 cm

Dark red (2.5YR4/6);
light medium clay; strong very coarse blocky, parting to strong medium, and moderate-strong fine subangular blocky structure; very firm to strong consistence (slightly moist); pH 6.8; gradual change to:

B22k

55-80 cm

Reddish brown (5YR4/4) with dark red (2.5YR4/6) mottles common;
light clay (very fine sand); weak-medium coarse blocky structure; very firm to strong consistence (slightly moist); few (2-5%) hard and semi-hard coarse to very coarse calcareous nodules (6-50 mm); many very fine macropores; pH 8.8; clear change to:

2A11k

80-120 cm

Brown (7.5YR4/4) with strong brown (7.5YR5/6) mottles;
sandy clay loam (medium sand); weak-moderate very coarse blocky structure; very firm consistence (slightly moist); few (2-5%) semi-hard calcareous nodules (2-6 mm); many macropores; pH 8.8; gradual change to:

2A12

75-100 cm

Brown (7.5YR5/4);
light clay (fine sandy); few (2-5%) coarse (6-20 mm) tubular calcareous segregations with some patches of fine-earth carbonates; pH 8.3:

2B23

120+ cm

Brown (7.5YR5/4) with strong brown (7.5YR5/6) mottles;
sandy clay loam (fine-medium sand); weak-moderate coarse blocky structure; very firm consistence (slightly moist); very few (2%) semi-hard calcareous nodules (2-6 mm); many macropores; pH 8.8.

Note: This horizon continues to approximately 250 cm depth and overlies more clayey material.

Key Profile Features
  • Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
  • Buried soil horizons (of older soils) present.

Soil Profile Characteristics

pH
Salinity Rating
Surface
(A1 horizon)
Moderately Acid
Medium
Non-Sodic
None
Subsoil
(B21 horizon)
Slightly Acid
Medium
Sodic
Slight1
Deeper subsoil
(at 120+ cm)
Strongly Alkaline
Low
Sodic
Slight-Moderate
1 Strong dispersion after remoulding.

Photos Werribee WP2 graphs

Horizon
Horizon Depth
(cm)
pH
(water)
pH
CaCl2
EC
dS/m
NaCl
%
Exchangeable Cations
Boron
(CaCl2)
mg/kg
Ex Al
mg/kg
Ex Ac
meq/100g
Field
pF2.5
Wilting Point
pF4.2
Coarse Sand
(0.2-2.0mm)
Fine Sand
(0.02-0.2mm)
Silt
(0.002-0.02mm)
Clay
(<0.002mm)
Ca
Mg
K
Na
meq/100g
A1
0-10
5.6
5.3
0.42
0.04
5.3
2.7
0.8
0.2
<10
5.8
24.3
9.0
9
42
21
18
A12
10-20
6.0
5.7
0.30
0.04
4.1
2.3
0.4
0.2
<10
3.7
25.9
7.3
7
46
23
19
B21
20-55
6.8
6.4
0.45
0.07
4.2
4.2
0.7
0.7
2.2
34.1
12.5
4
34
18
42
B22k
55-80
8.8
8.3
0.71
0.09
4.6
6.8
0.8
3.5
4.4
27.1
11.3
3
41
18
33
2A11k
80-120
8.8
8.2
0.29
0.03
3.8
5.8
0.6
1.6
1.9
23.6
8.9
7
54
14
22
2A12
120+
8.8
8.3
0.19
6.7
5.1
0.44
1.1
1.3
46.7
12.1
7
53
17
19

<2µm Clay Mineralogy
Horizon
Depth
cm
Quartz
Mica/Illite
Kaolin
Goethite
Orthclase
Smectite
B21
20-55
3
44
51
2
<1
-
2A12
120+
4
34
30
3
<1
28

2µm Cation Exchange Capacity
Horizon
Depth
cm
SiO2
%
Al2O3
%
MgO
%
P2O5
%
K2O
%
TiO2
%
MnO
%
Fe2O3
%
BaO
%
Sum
%
CEC
cmol/kg
B21
20-55
42.5
26.3
1.1
0.6
3.4
1.0
0.0
10.2
1.8
87.0
25
2A12
120+
46.7
22.8
1.9
0.3
3.1
1.0
0.1
10.2
2.7
88.9
37


Management Considerations:

Whole Profile
  • Management strategies for all soils should aim to increase organic matter levels in the surface soil; minimise the degradation of soil aggregates and porosity; promote the development of stable biopores; improve the calcium status of the cation exchange complex (particularly when sodium is a significant part), and break up any hardpans. Less frequent tillage; using less aggressive implements, and working the soil at optimum moisture content can all assist in maintaining soil aggregation and porosity as well as reducing the breakdown of organic matter.
Surface (A) Horizons
  • The surface horizons have high fine sand contents which makes them prone to becoming hardsetting and will result in the soil becoming ‘powdery’ when cultivated dry. Increasing organic matter levels will assist in improving surface soil aggregation and ameliorating the hardsetting condition. Organic matter levels will decline under cropping, but can be improved by adopting practices such as minimum tillage, residue retention, and utilising pasture rotations.
  • The subsurface (A12) horizon disperses after remoulding. This indicates that mechanical disturbance to this horizon whilst in a moist-wet condition may result in structural degradation (e.g. development of cultivation pan).
Subsoil (B) Horizons
  • The subsoil is sodic and slightly dispersive. Some restriction to water movement into the subsoil is expected. The subsoil is, however, relatively well structured for a Sodosol – in that it parts into a strong grade of medium to fine sized subangular blocky shaped peds. This would provide a more favourable structure for root movement in the upper subsoil compared to other more coarsely structured sodic subsoils.
  • The subsoil disperses strongly after remoulding. Care should be taken not to disturb the subsoil (e.g. by tillage) when in a moist to wet condition as structural degradation is likely to occur.
Notes
Soil profile described by Mark Imhof and Siggy Engleitner (30 April, 2004).
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