Victorian Resources Online (archived)

SFS22

Location: Rocklea

Australian Soil Classification: Vertic (& Calcic), Mottled-Mesonatric, SODOSOL

General Landscape Description: Gently undulating coastal plain with very low relief.
Site Description: Simple slope (1-2%) with southerly aspect.
Land Use: Pasture / crop rotations. Southern Farming Systems (SFS) trial site.
Geology: Neogene sediments (Hanson Plain Sand).

SFS22 Landscape

Soil Profile Morphology:

Surface Soil			SFS22 profile
Ap	0-10 cm	Dark brown (10YR3/3); loamy sand; apedal structure; loose with some weak fragments; pH 6.0; abrupt change to:
A2(e)	10-20/35 cm	Dark yellowish brown (10YR4/4), pale brown (10YR6/3 dry) and light yellowish brown (10YR6/4) conspicuously bleached (10YR7/3 dry) ; sandy loam; few coarse buckshot/ferruginous gravel in thicker zones of A2; apedal structure; firm consistence dry; pH 5.7; sharp and wavy change to: NOTE: Horizon is of variable thickness. It is more bleached where it is thicker and closer to the A2/B21 boundary.
Subsoil
B21t	20/35-65 cm	Brown (10YR4/3) ped faces with yellowish brown (10YR5/6) matrix with dark yellowish brown (10YR4/6) mottles; medium clay; coarse prismatic (some peds tending to have domed tops), parting to coarse (20 mm) angular blocky, polyhedral as well as lenticular structure; smooth faced peds; pH 7.2; gradual or diffuse change to:
B22t	65-95 cm	Dark yellowish brown (10YR4/6) matrix and yellowish red (5YR4/6) ped surfaces; medium clay; angular blocky and lenticular structure; many vertic features; pH 8.7; clear change to:
B23ss	95-120+ cm	Strong brown (7.5YR5/8) matrix with yellowish red (5YR4/6) ped surfaces/infill; light clay; contains soft yellow (10YR7/6) calcium carbonate; visible effervescence; pH 9.3. NOTE: Thick vertical lenticular peds in the subsoil.

Part of a lenticular ped found within the subsoil.

A fragment from the deeper subsoil B23k, note the calcium carbonate.

Key Profile Features:

Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
Lateral variation in soil profile due to gilgai microrelief (e.g. variations in depth of subsurface A2 horizon; variation in amount of ironstone gravel).

Soil Profile Characteristics:

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Moderately Acid	Low	Non-Sodic	Minimal Aggredation
Subsoil (B21 horizon)	Near Neutral	Low	Strongly Sodic	Moderate¹
Deeper subsoil (at 95-120 cm)	Very Strongly Alkaline	Medium	Strongly Sodic	Slight²

¹ Strong dispersion after remoulding. ² Moderate dispersion after remoulding.

The pH in the surface is moderately acid. The pH in the upper subsoil is near neutral becoming very strongly alkaline with depth.

The surface is non sodic. The subsoil is strongly sodic.

The clay content in the surface is low and sharply increases at the surface / subsoil interface.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC dS/m	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
Ap	0-10	6.0	5.6	0.21		6.1	1.2	0.50	0.41
A2	10-35	5.7	5.3	0.14		1.1	0.46	<0.05	0.19
B21	35-65	7.2	6.4	0.31	0.03	4.9	7.8	0.4	4.2
B22	65-95	8.7	7.9	0.54	0.06	4.6	10	0.4	5.7
B23	95-120	9.3	8.6	0.69	0.07	4.7	9.9	0.4	5.6

Horizon	Horizon Depth (cm)	Oxidisable Organic Carbon %	Total Nitrogen %	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)


Ap	0-10	1.9	0.27	<10	6.3	15	9	14	63	8	8
A2	10-35			<10	1.7	11	2	16	68	9	5
B21	35-65					36	23	5	23	4	65
B22	65-95					39	20	6	35	5	51
B23	95-120

Management Considerations:

Whole Profile

Plant available water capacity (PAWC) is considered to be very low (estimated at 33 mm) in the upper 30 cm of this soil profile. Effective rooting depth (ERD) is restricted to 30 cm due to the highly sodic subsoils.
The texture contrast and the sodic (ESP is around 25%) subsoil restricts drainage and the soils readily become waterlogged in winter.
The sandy topsoil is very susceptible to soil structure decline; the weak aggregation is readily destroyed by cultivation and the soils are prone to compaction. Bare soil is vulnerable to structural breakdown by rain (slaking and sealing) and to erosion by water. In dry conditions these soils are known to be vulnerable to wind erosion.
Plough pans are common in these soils. Disruption of pans by tillage is short lived unless controlled traffic is deployed in cropping situations. Raised beds have been used with some degree of success in these soils but the unstable topsoils do not lend themselves well to bed survival.
Other parts of the paddock were reported as having a high gravel or buckshot content though little was found in this pit.
See also SFS19 for related soil. Principle difference between this and SFS19 is the presence of calcareous material at 1 metre and the higher sodicity (SFS19 is only marginally sodic).

Comments from Landholder: At this pit site very little iron rich gravel was found but it is known that more substantial patches of gravel exist in this paddock.

Profile Describe By: Richard MacEwan (May 1999).

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