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SW103

Location: Lara

Australian Soil Classification: Epicalcareous - Epihypersodic, Massive, Red VERTOSOL (moderate profile depth)

General Landscape Description: Near level plain.
Site Description: Broad flat ridge with easterly aspect slope <1%.
Geology: Quaternary Basalt.


Soil Profile Morphology:


Surface Soil


Ap0-12 cmBrown (7.5YR4/3 moist); hardsetting surface condition; light clay; apedal structure; contains shelly material including intact shells; pH 7.9; clear and smooth change to:
Image: SW103 Profile
SW103 Profile - Note: Surface stripped from soil profile.
Subsoil

B21t12-30 cmDark reddish brown (5YR3/3 moist); medium heavy clay; fine prismatic structure, parting to fine polyhedral; pH 9; clear and smooth change to:
B22ss30-60/75 cmDusky red (2.5YR3/3), becoming brown (7.5YR4/3) at depth; medium heavy clay; prominent slickensides (up to 30 cm across); pH 9.5; clear and wavy change to:
B23k60/75-80/100 cmReddish yellow (7.5YR6/8) becoming reddish yellow (7.5YR7/8) at depth; abundant soft calcium carbonate (CaCO3); irregular change to:
C80/100+ cmWeathering vesicular soft greenish basalt; tongues of calcium carbonate (CaCO3) from B23k above; some biological activity present (ant nests).

Key Profile Features:
  • High (>35%) clay content throughout the soil profile.
  • Massive (hardsetting) surface horizon.
  • Vertic features (slickensides) in subsoil.
  • Calcium carbonate segregations in deeper subsoil.
  • Moderate soil profle depth – overlying weathering fractured basalt.

Soil Profile Characteristics:

pH
Salinity Rating
Surface
(A1 horizon)
Slightly Alkaline
Low
Non-Sodic
None1
Subsoil
(B21 horizon)
Strongly Alakaline
Low
Strongly Sodic
Moderate-Strong
Deeper Subsoil
(at 40-55 cm)
Very Strongly Alkaline
Medium-High
Strongly Sodic
Strong-Complete
1 Strong dispersion after remoulding.


Image: SW103 Graphs

The surface is slightly alkaline. The subsoil is strongly alkaline becoming very strongly alkaline at depth.Salinity rating is low in the surface and upper subsoil becoming medium to high at depth.The soil is non sodic in the surface and strongly sodic in the subsoil.The clay content is high throughout the profile.

Horizon
Sample Depth
(cm)
pH
(water)
pH
(CaCl2)
EC
1:5
NaCl
%
Exchangeable Cations
Ca
Mg
K
Na
meq/100g
A1
0-10
7.9
7.3
0.2
21
4.1
1.5
0.8
B21
15-30
9
8
0.42
0.02
15
8.8
1.4
7
B22
40-55
9.5
8.8
0.73
0.04
7.7
16
1.9
12

Horizon
Sample Depth
(cm)
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
2.3
0.26
33.1
18.4
12
21
17
42
B21
15-30
55.3
29.6
5
14
11
65
B22
40-55
63.7
35.3
4
14
17
58


Management Considerations:

Whole Profile

  • The relatively high wilting point (i.e. 18%) indicates that plants will be unable to fully utilise light rains when the soil is dry.
  • Tillage of cracking clay soils should be avoided if the soil is wet (i.e. wetter than the plastic limit). At such moisture conditions, excessive tillage, trafficking or over stocking could result in structural damage (i.e. compaction, smearing) occurring. Ideally tillage and trafficking should take place when the soil is drier than the plastic limit.

Profile Described By:
Richard McEwan (February 1999).
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