SW81

Location: Yeo

Australian Soil Classification: Eutrophic, Mottled--Subnatric, Black SODOSOL

General Landscape Description: Low undulating hills.
Site Description: Gentle simple slope.
Geology: Basalt plain.


Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Dark brown (7.5YR3/2 moist); sandy loam; pH 5.3:	SW81 Profile. Note: Surface (A1) horizon has been stripped from the soil 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 gray (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; abrupt change to:
B22	55-100 cm	Light olive brown (2.5Y5/3 moist); few (<10%), brownish yellow (10YR6/6 moist) and very dark gray (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	Medium	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Low	Sodic	Strong1
Deeper Subsoil (at 55 - 100 cm)	Slightly Acid	Low - Medium	Strongly Sodic	Strong1
1 Complete dispersion after remoulding.

The surface soil is strongly acid. The subsoil is slightly acid.

Salinity rating is medium in the surface becoming low in the subsoil, increasing to moderate levels in the deeper subsoil.

The soil is non sodic in the surface and sodic in the upper subsoil becoming strongly sodic in the deeper subsoil.

The clay content increases markedly at the A/B boundary.

Horizon	Sample 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	0.07	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	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	14	4.1	0.35	20.9	10.9	28	43	9	13
A2	10-30	<10	2.8			9.4	1.7	33	51	6	3
B21	30-55		13			40.9	23.8	12	23	5	59
B22	55-100		9			44.2	24.1	11	23	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.