Victorian Resources Online (archived)

LS17

Location: Big Desert.

Australian Soil Classification: Calcic, Mottled-Subnatric, Yellow SODOSOL (sandy surface horizon)

Northcote Factual Key: Dy 5.43
Great Soil Group: solodized solonetz

General Landscape Description: Crest of a dune on a gently undulating sand rise (dunefield) south of the Big Desert.
Native Vegetation: Mallee.

LS17 Landscape

Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Light yellowish brown (10YR6/4); loamy sand; weakly structured; pH 7.7:	LS17 Profile
A2	10-15 cm	Light yellowish brown (10YR6/4) conspicuously bleached; fine sand; pH 8.6; sharp and wavy change to:
Subsoil
B21	15-30 cm	Light yellowish brown (10YR6/4) with brownish yellow (10YR6/6) mottles; coarse sandy clay loam; weak to moderate coarse columnar structure with hard bleached capping; strong consistence dry; pH 8.9; clear and wavy change to:
B22k	30-60 cm	Light yellowish brown (10YR6/4) with yellowish red (5YR5/6) mottles; light medium clay (sandy); moderate coarse prismatic, parting to strong coarse blocky structure; ped faces may have a discontinuous carbonate coating; pH 9.4:
B31k	60-100 cm	Red (2.5YR4/8) with strong brown (7.5YR5/6) mottles; coarse sandy clay loam; massively structured; strong consistence dry; contains few (5 %) calcareous nodules; pH 9.6:
B32	100-150 cm	Light yellowish brown (10YR6/4) with yellowish red (5YR5/6) mottles; medium clay (sandy); moderate medium blocky structure; contains very few (< 2%) hard carbonate nodules; pH 9.8:
B33	150+ cm	Yellowish red (5YR5/6) with light yellowish brown (10YR6/4) mottles; medium clay (sandy); pH 9.8.

Key Profile Features:

Distinct texture contrast between sandy surface (A) horizons and clay subsoil (B21) horizon.
Soft surface soil condition (ie. not hard-setting).
Thin, conspicuously bleached subsurface (A2) horizon.
Coarse columnar structure with hard bleaching capping at top of B horizon.

Soil Profile Characteristics:

	pH	Salinity	Sodicity	Dispersion
Surface (A1 horizon)	Slightly Alkaline	Very Low	Non-Sodic	None
Subsoil (B21 horizon)	Strongly Alkaline	Very Low	Strongly Sodic	Strong
Deeper Subsoil (at 1 metre)	Extremely Alkaline	Low-Medium	Strongly Sodic	Strong

The surface soil is slightly alkaline. The subsoil is strongly alkaline becoming extremely alkaline at depth.

The salinity rating is very low in the surface and upper subsoil becoming moderate with depth.

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

Chemical and Physical Analysis:

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl₂)	EC dS/m	Sodium Chloride %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-10	7.7	7.1	<0.05		0.9	0.4	0.2	0.1
A2	10-15	8.6	7.9	<0.05		0.6	02	0.1	0.1
B21	15-30	8.9	7.8	0.15		4.8	4.6	0.7	1.7
B22	30-60	9.4	8.5	0.32	<0.05	6.7	8	1.2	3.4
B31	60-100	9.6	8.4	0.2		3.4	5.7	0.7	2.9
B32	100-150	9.8	8.8	0.46	<0.05	3	8	1	7.5
B33	150+	9.8	8.8	0.55	<0.05	2.9	7.8	1	7.9

Horizon	Horizon Depth (cm)	Total Nitrogen %	Oxidisable Organic Carbon %	Field Capacity pF2.5	Wilting Point pF4.2


A1	0-10	<0.05	0.3	2.9	1.4
A2	10-15	<0.05	0.1	1.9	1.1
B21	15-30			19.1	11.3
B22	30-60
B31	60-100
B32	100-150
B33	150+

Management Considerations:

Surface (A) Horizons

The shallow sandy surface horizons are prone to wind erosion which would expose the strongly sodic and dispersive subsoil to water erosion. Organic matter levels and surface cover need to be maintained to restrict wind erodibility.
The surface soil has a very low inherent fertility (based on the sum of the exchangeable basic cations) and low organic matter and total nitrogen levels. Increasing organic matter levels will improve soil nutrient holding capacity.
The available water capacity is very low for the surface horizons due to their sandy texture. However, the low wilting point value (ie.1.5%) suggests that plants would be able to utilise light rains falling on dry soil. However, overall plant available water capacity will be very low.

Subsoil (B) Horizons

The dense and coarsely structured subsoil is strongly sodic and dispersive. Root and water movement into the subsoil will be significantly restricted as a result. The hard bleached capping will present a major barrier to root movement. The conspicuously bleached subsurface (A2) horizon indicates that periodic waterlogging may occur above the subsoil following heavy rains. Lateral movement of water (downslope) above this horizon is likely to occur.
The strongly alkaline subsoil indicates that some nutrients (eg. iron, manganese, copper and zinc) may be poorly available to plants. Plant tissue analysis can be performed to assess deficiencies.

Profile Described By: Mark Imhof, John Martin, David Rees, Austin Brown, Geof Morrow, Sonia Thompson (May 1994).

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