GN16

Group: Nagambie Landcare Group	Australian Soil Classification: Vertic (and Magnesic) Mesonatric, Grey SODOSOL.
Northcote Factual Key: Dy 2.42	Great Soil Group: solodic soil
General Landscape Description: Crest of a gently undulating sedimentary rise. This site has been disturbed due to the removal of gravel from the surface horizons.

GN16 Landscape

Soil Profile Morphology

Surface Soil

A1	0-15 cm	Dark brown (7.5YR3/2) light fine sandy clay loam; weak, medium to coarse polyhedral structure; very firm consistence dry; pH 5.6; abrupt change to:	GN16 Profile
A2	15-20 cm	Discontinuous A2 horizon; greyish brown (10YR5/2) conspicuously bleached fine sandy clay loam; very strong consistence dry; contains a very heavy (90%) amount of coarse gravel (ironstone and siltstone); abrupt change to:
Subsoil
B21	20-70 cm	Pale brown (10YR6/3) medium to heavy clay with gravel segregations; moderate coarse to very coarse blocky structure; cracks deeply; very strong consistence dry; pH 7.5; diffuse and wavy change to:
B/C	70-120 cm	Light grey (2.5Y7/2) silty clay loam (50% substrate); moderate very coarse prismatic structure:
C	120+ cm	Weathered base rock (siltstone).

Key Profile Features

Strong texture contrast between the surface (A) horizons and the subsoil (B) horizons.
Discontinuous A2 horizon.
Hardsetting surface.

Key Profile Characteristics

Management Considerations:

Surface (A) Horizons

The moderately acid surface horizon indicates that aluminium toxicity may become a problem, inhibiting the growth of plants.
Organic carbon and nitrogen levels are relatively high.
The available water holding capacity of the surface soil is relatively high but overall plant available water will be restricted by limited available water in subsoil.

Subsoil (B) Horizons

The coarsely structured and dense subsoil is strongly sodic and strongly dispersive. This indicates that water and plant root movement into the subsoil will be restricted. The presence of a bleached A2 horizon (although discontinuous) above the sodic subsoil indicates that periodic waterlogging may occur in patches.
The subsoil has a very low calcium:magnesium ratio (0.1). This will also result in structural problems restricting root and water movement into the subsoil. A calcium deficiency may also occur.
The subsoil varies deeply and will significantly swell and shrink upon wetting and drying. This will have implications for building foundations etc.

Comments from Landholder:

The subsoil is not acidic as lucerne is growing.
Area has been extensively stripped for gravel approximately 50 years ago. Gypsum and topsoil were added before cropping.
Gypsum has been applied at the rate of 1 tonne per hectare.
Superphosphate was added in early 1995 (added annually prior to 1993).

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