SW78

Location: Yeo

Australian Soil Classification: Bleached-Vertic, Eutrophic, Black CHROMOSOL

General Landscape Description: Gently undulating rises.
Site Description: Flat to gently inclined plain.
Geology: Mapped as Tertiary-Gellibrand Marl

SW78 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Very dark grayish brown (10YR3/2 moist), light brownish gray (10YR6/2 dry); fine sandy loam; moderately pedal; pH 5.2; clear change to:	SW78 Profile. Note: Surface (A1) horizon has been stripped from the soil profile
A2e	10-50 cm	Light brownish gray (10YR6/2 moist), conspicuously bleached (10YR8/1 dry); light fine sandy clay loam; rusty mottles; minor fine gravel and buckshot gravel; apedal; massive; weak consistence; pH 5.8; sharp and slightly wavy change to:
Subsoil
B21t	50-80 cm	Black (10YR2/1 moist) with fine, distinct, yellowish brown and red mottles; heavy clay; few, very coarse (>300 mm) prismatic tending to columnar, parting to coarse prismatic and medium angular blocky structure; deep vertical cracks to full depth of trench (>1.7 m); pH 6.4; gradual change to:
B22ss	80-110 cm	Very dark grayish brown (2.5Y3/2 moist); heavy clay; coarse lenticular structure; slickensides; pH 6.7; diffuse change to:
B23	110+ cm	Brown (10YR4/3 moist); distinct, yellowish brown (10YR5/6-5/8 moist) and dark red mottles becoming dominant and prominent at depth; very few (<0.2%) fine rounded buckshot gravel; pH 6.7.

Prismatic structure in the B21 subsoil horizon.		Lenticular ped in the B22 subsoil horizon.

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Very Low	Non-Sodic	None1
Deeper Subsoil (at 80-130 cm)	Slightly Acid	Low	Non-Sodic	None
1 Strong dispersion after remoulding.

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

Salinity rating is low in the surface becoming very low in the subsoil.

The soil is non sodic throughout.

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

Horizon	Sample Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-10	5.2	4.6	0.14	3.6	1.1	0.26	0.29
A2	25-45	5.8	5.1	0.06	2.3	1.2	0.07	0.15
B21	55-75	6.4	5.3	0.11	5.8	12	0.24	1.4
B22	85-100	6.7	5.8	0.13	4.5	13	0.24	1.8
B23	100+	6.7	6	0.21

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	27	15	7.2	0.36	30.4	10.3	9	50	23	10
A2	25-45	<10	7.4			22.2	6.1	7	53	20	17
B21	55-75	<10	14			47.9	29.8	1	12	5	77
B22	85-100	<10	11			48.7	29.5	2	13	6	79
B23	100+

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 will restrict the growth of roots down the profile.