Victorian Resources Online (archived)

SW87

Location: Winchelsea

Australian Soil Classification: Epihypersodic-Endocalcareous, Self-Mulching, Black VERTOSOL

General Landscape Description: Gently undulating plains / rises.
Site Description: Gently inclined simple slope, easterly aspect.
Geology: Quaternary-Newer Volcanics - Basalt

SW87 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-15 cm	Very dark grey (10YR3/1); thin cracking self-mulching surface condition; light medium clay; coarse blocky structure below surface; smooth faced peds; strong consistence dry; pH 5.7; gradual change to: NOTE: In the trench spoil the surface material had self-mulched to <5 mm sized peds.	SW87 Profile. Note: Surface (A1) horizon has been stripped from the profile.
Subsoil
B21ss	15-50/70 cm	Black (2.5Y2.5/1); heavy clay; strong coarse irregular lenticular structure; prominent slickensides increasing in size with depth; strong consistence dry; pH 8.0; clear and wavy change to:
B22k	50/70+ cm	Olive brown (2.5Y4/3t) and fine dark yellowish brown (10YR4/6 moist) mottles; medium clay to light medium clay; vertic properties; white soft calcium carbonate present; pH 8.7.

South West Gasp Pipeline SW87 Lenticular

Lenticular peds (B22ss).

Key Profile Features:

Shallow self-mulching surface.
High (>35%) clay content throughout the soil profile.
Vertic features i.e. slickensides and lenticular peds in subsoil.
Calcium carbonate in deeper subsoil.

Soil Profile Characteristics:

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Low	None	None
Subsoil (B21 horizon)	Moderately Alkaline	Medium - High	Strongly Sodic	Strong
Deeper Subsoil (at 60+ cm)	Strongly Alkaline	Very High	Strongly Sodic	None¹
¹ No dispersion possibly due to high levels of soluble salts.

The surface soil is moderately acid. The subsoil is moderately alkaline becoming strongly alkaline with depth.

Salinity rating is low in the surface becoming medium in the subsoil and very high with depth.

The soil is non sodic in the surface. The subsoil is strongly sodic.

High clay content 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	5.7	5	0.24		16	12	1.4	1
Bss	35-55	8	7.3	0.76	0.15	15	15	0.8	5.5
Bk	60+	8.7	8.3	1.6	0.35	12	16	0.4	7.2

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	16	5.0	0.41	48.5	28.2	10	20	14	44
Bss	35-55					54	25.6	5	19	15	56
Bk	60+					44.3	23.1	2	12	9	41

Management Considerations:

Surface (A) Horizon

The very high wilting point (i.e. 28%) 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.
When the soil is dry, heavy rains will move from soil cracks. This rapid recharge can be valuable for the survival of plants near wilting. When wet, the soil will swell and further infiltration of water will be relatively slow.

Subsoil (B) Horizons

The subsoil displays vertic features (i.e. slickensides and lenticular peds) and will therefore experience shrinking and swelling during wetting and drying cycle. This may disturb the roots of some plant species and has engineering implications (e.g. disturbance to building foundations).
The dense and coarsely structured subsoil is strongly sodic and disperse strongly in water. This will result in restricted root and water movement into the subsoil.

Notes

Bk becomes thicker to the west, of this site whilst immediately to the east the profile is shallow and rocky and has a thick calcium carbonate (CaCO₃) layer.

Profile Described By: Richard McEwan (March 1999).

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