Victorian Resources Online (archived)

SG8

Location: Middle Tarwin	Australian Soil Classification: Melacic-Parapanic, Humic/Humosesquic, Semiaquic PODOSOL (f. Grey KUROSOL¹).
Great Soil Group: humus podzol	Geology: Tertiary sediments.
General Landscape Description: Elevated plateau on a gently undulating rise (slope <3%).	Soil Mapping Unit: Inverloch.
Site Description: Bushland Reserve.	Native Vegetation: Includes Messmate (Eucalyptus obliqua) and Brown Stringybark.

Site SG8 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-20 cm	Black (10YR2/1); fine sandy loam; very weak fine blocky structure; firm surface condition; firm consistence dry; contains a few (5%) quartz gravels (2-3 mm diameter); pH 4.9; clear change to:	Site SG8 Profile
A2	20-30 cm	Pinkish grey (7.5YR6/2); fine sandy loam; structureless; strong consistence dry; contains many (25%) quartz gravels (2-5 mm diameter); dark staining in patches; pH 4.8: abrupt and wavy change to:
Subsoil
Bh	30-40 cm	Black (10YR2/1); loam; moderate very fine crumbly polyhedral structure; firm consistence dry; pH 4.7; sharp change to:
Bhs	40-65 cm	Variably cemented coffee rock material; pH 5.1; sharp change to:
D21	65-75 cm	Light brownish grey (10YR6/2) with yellowish brown (10YR5/6) mottles; light clay (gritty); strong fine polyhedral structure; weak consistence moist; contains a common (15%) amount of quartz gravel (2-4 mm diameter); pH 4.8; clear change to:
D22	75-95 cm	Light grey (10YR7/1) with yellowish brown (10YR5/6) mottles; heavy clay (kaolinitic); flaky structure; very firm consistence moist; pH 4.5; gradual change to:
D23	95+ cm	White (10YR8/1) with yellowish brown (10YR5/6) mottles; heavy clay (kaolinitic); flaky structure; very firm consistence moist; pH 4.4.
¹ It appears that the Podosol is forming in the A horizon of an older Grey Kurosol.

Key Profile Features:

Subsoil accumulation of organic matter humic layer (30 - 40 cm) and organic matter/iron coffee rock (40-65 cm).

Soil Profile Characteristics:

	The pH is very strongly acid throughout most of the profile and becomes extremely acid at approximately one metre depth.		Exchangeable aluminium levels are high throughout most of the soil profile.
	The soluble salt levels are very low throughout the soil profile.		The clay content increases markedly from the surface horizons to the cemented coffee rock and then to the D horizons.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC 1:5	Exchangeable Cations
					Ca	Mg	K	Na
					meq/100g
A1	0-20	4.9	3.9	0.06	1.7	0.8	0.2	0.1
A2	20-30	4.8	4.0	<0.05	0.2	0.3	0.1	<0.1
Bh	30-40	4.7	3.9	0.09	0.5	1.9	0.1	0.3
Bhs	40-65	5.1	4.7	0.08	0.1	0.2	0.1	0.1
D21	65-75	4.8	4.2	0.09	0.1	0.5	0.1	0.1
D22	75-95	4.5	4.0	0.12	0.1	0.6	0.1	0.1
D23	95+	4.4	3.8	0.08	0.1	0.6	0.1	0.1

Horizon	Horizon Depth (cm)	Exchangeable Aluminium mg/kg	Exchangeable Acidity meq/100g	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	0-20	170	20.2	30	8	18	37	26	10
A2	20-30	97	6.2	14	3	24	39	28	9
Bh	30-40	200	45.8	33	19	13	22	7	36
Bhs	40-65	150	38.6			10	14	12	39
D21	65-75	270	19.8			9	15	11	60
D22	75-95	260	12.4			8	18	11	60
D23	95+	190	12.4

Management Considerations:

Whole Profile

Plant Available Water Capacity (PAWC) is considered to be very low (estimated at approximately 45 mm). This is based on available laboratory data and assumes an effective rooting depth of 40 cm. Rooting depth is likely to be limited by the "coffee rock" layer that begins at 40 cm depth.
The presence of a subsoil humic layer (30 - 40 cm) indicates the soil profile is likely to suffer at least some short-term saturation of the B horizons.

Surface (A) Horizons

In the strongly acid surface horizon, the level of exchangeable aluminium measured in the laboratory is high (170 mg/kg). This is likely to restrict the growth of a number of aluminium sensitive species such as lucerne, medics, phalaris, subclover, white clover and tall fescue.

Deficiencies in molybdenum, phosphorus and potassium may occur in the very strongly acid surface soil. Raising the soil pH by lime application will enable phosphorous (from superphosphate application) to be more readily available. Liming is likely to improve pH and aluminium levels in the surface soil. Plant tissue analysis may give a more accurate assessment of molybdenum trace element requirements.

Subsoil (B) Horizons

Root and water movement is likely to be restricted by the "coffee rock" layer at 40 cm.

Profile Described By: Mark Imhof, Ian Sargeant and Sonia Thompson (21/6/95).

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