SW81

Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Dark brown (7.5YR3/2 moist); sandy loam; pH 5.3:	SW81 Profile
A2e	10-30 cm	Brown (10YR5/3 moist), conspicuously bleached (10YR7/2 dry); loamy sand; pH 5.5; sharp and smooth change to:
Subsoil
B21	30-55 cm	Very dark grey (10YR3/1 moist); with yellowish brown (10YR5/6 moist) mottles common (~10%); heavy clay; strong consistence [dry]; coarse prismatic to columnar, parting to coarse blocky structure; pH 6.4:
B22	55-100 cm	Light olive brown (2.5Y5/3 moist); few (<10%), brownish yellow (10YR6/6 moist) and very dark grey (10YR3/1 moist) mottles; heavy clay; very coarse prismatic to columnar, parting to coarse blocky structure; pH 6.7:
C	100+ cm	Weathered basalt.

• Conspicuously bleached subsurface (A2) horizon.
• Very coarse prismatic columnar structure in subsoil.
• Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low - Medium	Non-Sodic	None1
Subsoil (B21 horizon)	Slightly Acid	Low	Sodic	Strong
Deeper subsoil (at 55 - 100 cm)	Slightly Acid	Low - Medium	Strongly Sodic	Strong
1 complete dispersion after remoulding

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-10	5.3	4.7	0.24		4.4	2	1	0.48
A2	10-30	5.5	4.6	0.05		0.46	0.56	.07	0.14
B21	30-55	6.4	5.1	0.15		3.6	11	0.21	3.3
B22	55-100	6.7	5.7	0.39	0.06	4.2	11	0.2	5.7

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	14	20.9	10.9	27.5	43.4	8.5	12.5
A2	10-30	<10	2.8	9.4	1.7	32.8	51.2	5.5	3
B21	30-55		13	40.9	23.8	12.1	22.5	4.5	58.5
B22	55-100		9	44.2	24.1	10.9	22.8	5	58

Management Considerations:

Subsoil (B) Horizons

• The subsoil displays vertic features (i.e. slickensides) which indicates that significant shrinking and swelling occurs during wetting and drying cycles. This may have engineering implications and is likely to explain the variability in surface horizon depth across the trench.
• The dense and coarsely structured subsoil is strongly sodic and disperse strongly in water. This will result in restricted root growth down the soil profile.

Very coarse prismatic ped