PPW4

Location: Werribee

Australian Soil Classification: 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
Map Unit (Maher and Martin, 1979) : 10b

General Landscape Description: Level plain (with prior streams).
Site Description: Grazing paddock.
Geology: Quaternary alluvial (prior stream) and aeolian deposits.

Soil Pit WP1 Landscape

Surface Soil			Soil Pit PPW4 Profile
A1	0-12 cm	Brown (7.5YR4/4); fine sandy clay loam; weak coarse subangular blocky structure; very firm consistence (dry); pH 5.8; clear change to:
A21	12-20 cm	Brown (7.5YR4/6); heavy fine sandy clay loam; strong consistence (dry); macropores present; pH 6.7; clear change to:
A22	20-30cm	Brown (7.5YR4/6); heavy fine sandy clay loam; massive; strong consistence (dry); pH 7.2; abrupt change to:
Subsoil
B21	30-40 cm	Dark red (2.5YR4/8); medium clay; medium very coarse prismatic, parting to strong very coarse to coarse angular blocky structure; strong consistence (dry); few roots evident; pH 7.1; clear change to:
B22	40-60 cm	Dark red (2.5YR4/6); medium clay; medium very coarse prismatic, parting to strong coarse to medium angular, further parting to strong fine subangular blocky structure; few manganese flecks (5%); pH 7.5:; abrupt change to:
2B21	60-75 cm	Strong brown (7.5YR5/6 & 5/8); light clay (fine sandy); medium coarse blocky structure; pH 7.8:
2B22k	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	100-130 cm	Brown (7.5YR5/4); light clay; pH 8.2:
2B24	130-150 cm	Brown (7.5YR4/4); light medium clay; strong coarse blocky structure; pH 8.1.

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

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Very Low	Non-Sodic	None
Subsoil (B21 horizon)	Slightly Alkaline	Very Low	Sodic	Slight-Moderate1
Deeper subsoil (at 130-150 cm)	Moderately Alkaline	Low	Sodic	None1
1 complete dispersion after remoulding

Horizon	Horizon Depth (cm)	pH (water)	pH CaCl2	EC dS/m	NaCl %	Exchangeable Cations				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	0-12	5.7	5.5	0.19		5.1	3.9	0.39	0.36	<10	7.1	33.6	10.5	19	36	19	16
A21	12-20	6.7	6.3	0.11		3.5	2.8	0.12	0.38		3.7	27.7	5.4	16	43	21	16
A22	20-30	7.2	6.8	0.12		2.8	2.4	0.10	0.56		2.7	19.7	5.9	15	42	23	20
B21	30-40	7.1	6.4	0.15		5.9	7.4	0.34	1.6		7.2	34.7	18.1	3	26	21	48
B22	40-60	7.5	6.8	0.19		5.7	7.9	0.35	1.6		4.3	33.3	15.1	3	36	18	40
2B21	60-75	7.8	7.3	0.26	0.05	4.9	6.2	0.3	1.2			29.1	11.2	7	31	27	30
2B22k	75-100	8.3	7.9	0.33	0.05	7.2	7.0	0.4	1.4			27.8	12.5	4	28	33	32
2B23	100-130	8.2	7.5	0.2		5.1	5.1	0.55	1.5
2B24	130-150	8.1	7.4	0.21		5.3	6.6	0.39	1.7

• 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.

• 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 surface horizons are medium-thick in depth (i.e. 30 cm deep) – making these soils favourable for cropping.
• The subsurface (A22) horizon (at 20-30 cm depth) disperses completely 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).

• The upper subsoil is sodic and disperses (slight-moderate) in water. This indicates that root and water movement into the upper subsoil will be restricted. 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 completely 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.