PPW5

Location: Werribee - Research Farm
Aust. Soil Class.: Calcic, Subnatric, Red SODOSOL (medium to thick surface horizons)
Northcote Factual Key: Dr 2.13
Great Soil Group: red-brown earth
Previous Soil Type (Skene 1954): Werribee loam
Maher and Martin (1979) map unit: 10b
General Landscape Description: Level plain (with prior streams).
Site Description: Grazing paddock. This site is probably associated with a levee of a prior stream.
Geology: Quaternary alluvial (prior stream) and aeolian deposits.

WP2 Landscape

Soil Profile Morphology

Surface Soil			PPW5 Profile
A1	0-10 cm	Brown (7.5YR4/4), fine sandy clay loam; weak coarse, parting to moderate medium blocky structure; strong consistence (dry); compacted in upper 3 cm; pH 5.6; sharp change to:
A12	10-20 cm	Strong brown (7.5YR4/6); heavy fine sandy clay loam; moderate coarse blocky, parting to strong medium polyhedral structure; strong consistence (dry); pH 6.0; clear change to:
Subsoil
B21	20-55 cm	Dark red (2.5YR4/6); light medium clay; strong very coarse blocky, parting to strong medium, and moderate-strong fine subangular blocky structure; very firm to strong consistence (slightly moist); pH 6.8; gradual change to:
B22k	55-80 cm	Reddish brown (5YR4/4) with dark red (2.5YR4/6) mottles common; light clay (very fine sand); weak-medium coarse blocky structure; very firm to strong consistence (slightly moist); few (2-5%) hard and semi-hard coarse to very coarse calcareous nodules (6-50 mm); many very fine macropores; pH 8.8; clear change to:
2A11k	80-120 cm	Brown (7.5YR4/4) with strong brown (7.5YR5/6) mottles; sandy clay loam (medium sand); weak-moderate very coarse blocky structure; very firm consistence (slightly moist); few (2-5%) semi-hard calcareous nodules (2-6 mm); many macropores; pH 8.8; gradual change to:
2A12	75-100 cm	Brown (7.5YR5/4); light clay (fine sandy); few (2-5%) coarse (6-20 mm) tubular calcareous segregations with some patches of fine-earth carbonates; pH 8.3:
2B23	120+ cm	Brown (7.5YR5/4) with strong brown (7.5YR5/6) mottles; sandy clay loam (fine-medium sand); weak-moderate coarse blocky structure; very firm consistence (slightly moist); very few (2%) semi-hard calcareous nodules (2-6 mm); many macropores; pH 8.8.
		Note: This horizon continues to approximately 250 cm depth and overlies more clayey material.

Key Profile Features

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
• Buried soil horizons (of older soils) present.

Soil Profile Characteristics

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Medium	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Acid	Medium	Sodic	Slight1
Deeper subsoil (at 120+ cm)	Strongly Alkaline	Low	Sodic	Slight-Moderate
1 Strong dispersion after remoulding.

Horizon	Horizon Depth (cm)	pH (water)	pH CaCl2	EC dS/m	NaCl %	Exchangeable Cations				Boron (CaCl2) mg/kg	Ex Al mg/kg	Ex Ac meq/100g	Field pF2.5	Wilting Point pF4.2	Coarse Sand (0.2-2.0mm)	Fine Sand (0.02-0.2mm)	Silt (0.002-0.02mm)	Clay (<0.002mm)
						Ca	Mg	K	Na
						meq/100g
A1	0-10	5.6	5.3	0.42	0.04	5.3	2.7	0.8	0.2		<10	5.8	24.3	9.0	9	42	21	18
A12	10-20	6.0	5.7	0.30	0.04	4.1	2.3	0.4	0.2		<10	3.7	25.9	7.3	7	46	23	19
B21	20-55	6.8	6.4	0.45	0.07	4.2	4.2	0.7	0.7			2.2	34.1	12.5	4	34	18	42
B22k	55-80	8.8	8.3	0.71	0.09	4.6	6.8	0.8	3.5	4.4			27.1	11.3	3	41	18	33
2A11k	80-120	8.8	8.2	0.29	0.03	3.8	5.8	0.6	1.6	1.9			23.6	8.9	7	54	14	22
2A12	120+	8.8	8.3	0.19		6.7	5.1	0.44	1.1	1.3			46.7	12.1	7	53	17	19

	<2µm Clay Mineralogy
Horizon	Depth cm	Quartz	Mica/Illite	Kaolin	Goethite	Orthclase	Smectite
B21	20-55	3	44	51	2	<1	-
2A12	120+	4	34	30	3	<1	28

2µm Cation Exchange Capacity
Horizon	Depth cm	SiO2 %	Al2O3 %	MgO %	P2O5 %	K2O %	TiO2 %	MnO %	Fe2O3 %	BaO %	Sum %	CEC cmol/kg
B21	20-55	42.5	26.3	1.1	0.6	3.4	1.0	0.0	10.2	1.8	87.0	25
2A12	120+	46.7	22.8	1.9	0.3	3.1	1.0	0.1	10.2	2.7	88.9	37

Management Considerations:

Whole Profile

• Management strategies for all soils should aim to increase organic matter levels in the surface soil; minimise the degradation of soil aggregates and porosity; promote the development of stable biopores; improve the calcium status of the cation exchange complex (particularly when sodium is a significant part), and break up any hardpans. Less frequent tillage; using less aggressive implements, and working the soil at optimum moisture content can all assist in maintaining soil aggregation and porosity as well as reducing the breakdown of organic matter.

Surface (A) Horizons

• The surface horizons have high fine sand contents which makes them prone to becoming hardsetting and will result in the soil becoming ‘powdery’ when cultivated dry. Increasing organic matter levels will assist in improving surface soil aggregation and ameliorating the hardsetting condition. Organic matter levels will decline under cropping, but can be improved by adopting practices such as minimum tillage, residue retention, and utilising pasture rotations.
• The subsurface (A12) horizon disperses after remoulding. This indicates that mechanical disturbance to this horizon whilst in a moist-wet condition may result in structural degradation (e.g. development of cultivation pan).

Subsoil (B) Horizons

• The subsoil is sodic and slightly dispersive. Some restriction to water movement into the subsoil is expected. The subsoil is, however, relatively well structured for a Sodosol – in that it parts into a strong grade of medium to fine sized subangular blocky shaped peds. This would provide a more favourable structure for root movement in the upper subsoil compared to other more coarsely structured sodic subsoils.
• The subsoil disperses strongly after remoulding. Care should be taken not to disturb the subsoil (e.g. by tillage) when in a moist to wet condition as structural degradation is likely to occur.

Notes
Soil profile described by Mark Imhof and Siggy Engleitner (30 April, 2004).