Victorian Resources Online (archived)

GP62

Location: Cowwarr.	Australian Soil Classification: Melanic, Eutrophic, Black DERMOSOL.
Geology: Holocene fluvial deposits.	General Landscape Description: Level plain (0-1% slope).
Mapping Unit: Thomson.	Site Description: Dairy grazing paddock.

Site GP62 Landscape

Soil Profile Morphology:

Surface Soil

A11	0-25 cm	Very dark greyish brown (10YR3/2); fine sandy loam; strong medium polyhedral, parting to fine polyhedral structure; weak consistence dry; pH 5.7; gradual change to:	Site GP62 Profile
A12	25-40 cm	Very dark greyish brown (10YR3/2); fine sandy clay loam; strong medium polyhedral, parting to fine polyhedral structure; firm consistence dry; pH 6.4; gradual change to:
Subsoil
B21	40-60 cm	Very dark brown (10YR2/2); light clay; weak coarse prismatic, parting to strong medium to fine polyhedral structure; very firm consistence dry; pH 5.9; gradual change to:
B22	60-100 cm	Dark brown (10YR3/3) (with a bleached appearance on some ped faces); light clay (silty); moderate coarse prismatic, parting to strong medium polyhedral structure; strong consistence dry; pH 5.8; gradual change to:
B23	100-120 cm	Dark greyish brown (10YR4/2) with brown (7.5YR4/4) mottles and a bleached appearance on some ped faces; light clay silty; moderate coarse prismatic, parting to strong coarse polyhedral structure; strong consistence dry; manganese stains common; pH 6.6.

Key Profile Features:

Gradual increases in clay content with depth.
Well structured surface and upper subsoil.

Soil Profile Characteristics:

Horizon	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Moderate	Non-sodic	None
Subsoil (B21 horizon)	Moderately Acid	Very Low	Non-sodic	None
Deeper subsoil (at 1 m)	Slightly Acid	Very Low	Non-sodic	None

	The surface and upper subsoil is moderately acid. The deeper subsoil becomes slightly acid.		The profile is non-sodic throughout.
	The surface salinity rating is moderate. The subsoil salinity rating is very low throughout.		The clay content increases gradually with depth.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC 1:5	NaCl	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A11	0-25	5.7	5.1	0.22		10	2.9	0.24	0.29
A12	25-40	6.4	5.6	0.09		8.3	4.4	0.14	0.29
B21	40-60	5.9	4.9	0.09		5.7	6.1	0.14	0.44
B22	60-100	5.8	4.8	0.08		4.1	6.1	0.13	0.42
B23	100-120	6.6	5.5	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)


A11	0-25	<10	11		10.9	2	52	19	18
A12	25-40	-28	8.7		12.2	2	41	25	25
B21	40-60	<10	11		16.3	2	17	36	39
B22	60-100	<10	3.4		15.4	2	18	38	38
B23	100-120

Management Considerations:

Whole Profile

Plant Available Water Capacity (PAWC) is considered to be moderate-high (estimated at 130 mm) for this soil profile. This is based on an estimated effective rooting depth of 60 cm (ie. surface soil and upper subsoil). The denser and more coarsely structured deeper subsoil is likely to restrict rooting depth, although not as significantly as some of the more sodic subsoils in the region. PAWC has been estimated using a model developed by Littleboy (1995) which uses analytical data for clay %, silt %, fine sand %, coarse sand % and wilting point.
Infiltration of water will be rapid throughout the upper soil profile due to the well developed structure and pore space available.

Surface (A) Horizons

The level of soluble salts in the surface is moderate and may restrict the growth of salt sensitive species. These levels may be unnaturally high due to the effects of the dry season at the time of sampling (1996/97) and are likely to decline following heavy rainfall and/or irrigation.
The relatively deep surface soil is well structured (parting to many fine polyhedral shaped peds) and is friable when moist. Soil consistence when moist is also weak for this horizon. As a result of these attributes the surface soil will provide excellent seed-bed conditions, creating few limitations to root and water movement.
The surface (A1) horizon has a moderate nutrient holding capacity (based on the sum of the exchangeable calcium, magnesium and potassium cations).
The surface soil has a very high fine sand content (ie. 50%). Soils such as these rely on organic matter to maintain soil structure. Maintaining organic matter levels will also assist in improving soil fertility and water holding capacity.
Infiltration of water into the well structured surface soil will be quite high and this horizon will be well drained.

Subsoil (B) Horizons

The upper subsoil is well structured (parting to many fine polyhedral shaped peds). Root and water movement is not likely to be significantly restricted as a result.
The deeper subsoil (from 60 cm depth) becomes more coarsely structured and will be more restrictive to root movement.

Profile Described By: Mark Imhof, David Rees and Ian Sargeant (21/04/1998).

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