SW87

Soil Profile Morphology:

Surface Soil

A1	0-15cm	Very dark grey (10YR3/1 moist and 10YR4/1 dry); light medium clay; thin self-mulching surface; (note: in trench spoil this material had self-mulched to <5 mm peds); smooth-faced coarse blocky structure below surface; strong consistence, deep cracks to surface; pH 5.7; gradual change to:	SW87 Profile
Subsoil
B21ss	15-50/70 cm	Black (2.5Y2.5/1 moist, dry); heavy clay; strong, coarse (>100 mm) irregular lenticular structure, prominent slickensides increasing in size with depth; pH 8.0; clear and wavy change to:
B22k	50/70 cm+	Olive brown (2.5Y4/3 moist) and dark yellowish brown (10YR4/6 moist) mottles; white soft calcium carbonate (CaCO3); medium clay to light medium clay; vertic; fine, pH 8.3.

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.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Low	None	None1
Subsoil (B21 horizon)	Moderately Alkaline	Medium - High	Strongly Sodic	Strong
Deeper subsoil (at 50+ cm)	Strongly Alkaline	Very High	Strongly Sodic	None2
1 complete dispersion after remoulding 2 Possibly due to level of soluble salts.

Horizon	Horizon 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	Horizon Depth (cm)	Ex Al mg/kg	Ex Ac meq/100g	Field 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	48.5	28.2	9.2	19.6	14	44
Bss	35-55			54	25.6	4.8	19.4	15	55.5
Bk	60+			44.3	23.1	1.8	12.2	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.

• 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.

• 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.