Site 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

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	moderately acid	very low	non-sodic	_
Subsoil (B21 horizon)	slightly alkaline	very low	strongly sodic	strong

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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  This document was last reviewed on 22/12/2008