SW77

Location: Yeo

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

General Landscape Description: Gently undulating rises.
Site Description: Very gently inclined 1-2^o, western aspect.
Geology: Mapped as Tertiary Gellibrand Marl but more likely to be derived from Dilwyn, Eastern View Formation or Hanson Plain Sand.


SW77 Landscape

Soil Profile Morphology:

Surface Soil

Ap	0-20 cm	Dark greyish brown (10YR4/2 moist), greyish brown (10YR5/2 dry); fine sandy loam; apedal to weakly pedal; pH 5.0; clear change to:	SW77 Profile. Note: Surface (A1) horizon has been stripped from the soil profile
A2ec	20-50 cm	Brown (10YR5/3 moist), conspicuously bleached (10YR7/2 dry); fine sandy loam; gravel (mixed fine quartz and rounded ironstone fragments and buckshot 2-20 mm) making up ~80% of lower 20-25 cm; pH 5.8; abrupt and wavy (amplitude <150 mm) change to:
Subsoil
B21t	50-100 cm	Mottled yellow (10YR7/8 moist) and red (10R4/8 moist) in ped interiors; very dark greyish brown (10YR3/2 moist) on ped faces; medium heavy clay; strongly pedal, parting to coarse [40-100 mm] prismatic structure; slickensides (20-100 mm) across peds; material in soil heap very friable after rain and sun; roots to 1 m; pH 6.4; gradual change to:
B22tg	100 cm+	Matrix becoming yellower and greyer than B21 above; very pale brown (10YR7/3 moist), grey (10YR6/1 moist); red mottles still prominent; medium heavy clay; fine polyhedral structure; pH 6.4.

• Strong texture contrast between surface (A) horizons and subsoils (B) horizons.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Very Low	Non-Sodic	None
Deeper Subsoil (at 100+ cm)	Slightly Acid	Very Low	-	-

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	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
Ap	0-10	5	4.4	0.13		2.8	0.59	0.17	0.19
A2e	20-40	5.8	5	0.06		1.4	0.67	0.1	0.11
B21t	60-80	6.4	5.8	0.12		3.1	9.9	0.15	1.2
B22tg	100-120	6.4	5.6	0.16	0.02	2.1	10.0	0.15	1.9

Horizon	Horizon 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)
Ap	0-10	54	14	4.6	0.35	26.4	7.7	14	49	20	9
A2e	20-40	<10	4.1			18.2	4.3	22	47	19	10
B21t	60-80		11			41.5	29.1	3	10	3	79
B22tg	100-120

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.

• Mapped as Tmi, Gellibrand Marl on 1:50 000 Geology map (Beech Forest), flat gently sloping to the west 1-2^o.