Soil/Landform Unit 181

Remnant plateaux of this landform can be seen in the distance as a level plain delineating the extent of the dissection in the Heytesbury

Area:

16 717 ha

1.25% of CMA region

Small remnants of flat ferruginised plateau near Simpson and extending toward Irrewillipe are evidence of former widespread ferruginisation. Most ferricrete hill cappings have been removed by dissection, and this set of north-north-west and south-south-east orientated ridges is the only significant remnant to the west of the Otway Range. The most common soils have gradational profiles containing ferricrete ironstone. However, some profiles possess sand veneers in the surface horizons with hardpans overlying

mottled

clays. Drainage of the landscape is poor, particularly where hardpans occur, and seasonal waterlogging is a problem. The ridges have been extensively cleared as part of the Heytesbury Soldier Settlement Scheme and dairy farming is the main land use. There are problems arising from low soil fertility and exposure to wind. Only one small area of native vegetation remains in the study area.

Undulating plain west of Irrewillipe
	South-west gas pipeline works in 1998

Component	1	2	3
Proportion of soil-landform unit	65%	25%	10%
CLIMATE Rainfall (mm)	Annual: 800–950, lowest January (35), highest August (110)
Temperature (^oC)	Annual: 13, lowest July (8), highest February (18)
Seasonal growth limitations	Temperature: less than l0^oC (av.) June–August Precipitation: less than potential evapotranspiration late October–early April
GEOLOGY Age and lithology	Neogene ferruginised fluvio-marine sand and Recent clay, sand and gravel Veneer of Quaternary sand
Geomorphology	6.2.4 Plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Cleared areas: Dairy farming; some beef cattle grazing Minor cleared areas: Hardwood forestry production
TOPOGRAPHY Landscape	Very gently undulating plateau with north-west and south-east dissection
Elevation range (m)	150–170
Local relief (m)	10
Drainage pattern	Parallel
Drainage density (km/km²)	1.0
Landform	Plateaux
Landform element	Plain and very gentle slopes and crests	Gentle slopes	Lower slope and depression
Slope and range (%)	2 (0–14)	1 (0–3)	5 (0–9)
Slope shape	Straight (some convex)	Straight	Concave
NATIVE VEGETATION Structure	Open forest	Closed scrub	Open forest
Dominant species	E. obliqua, E. baxteri	Leptospermum juniperinum, Melaleuca squarrosa, E. nitida, Casuarina littoralis	E. baxteri, E. ovata
SOIL Parent material	Weathering ferruginised remnants	Ferruginised remnants covered by varying depths of sand	Alluvial sand and clay
Description (Corangamite Soil Group)	Grey sand soils (16) and mottled brown, grey, yellow and red texture contrast soils with ironstone (13)	Grey sand soils, structured clay underlay (16)	Yellow-brown gradational soils, coarse structure (34)
Soil type sites	SW60, SW65, SW61	SW59, SW63	SW62, SW64
Surface texture	Sandy loam	Sandy loam	Sandy loam
Permeability	Moderate	Low	Low
Depth (m)	1.7	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Low inherent fertility and phosphorus fixation lead to nutrient decline. Leaching of salts leads to increased salinity of drainage waters.	Low inherent fertility and leaching of permeable surface horizons lead to nutrient decline. Low permeabilities lead to seasonal waterlogging and soil compaction.	Low permeabilities and high seasonal watertables lead to seasonal waterlogging and soil compaction. Leaching of salts from landscape leads to increased salinity of drainage waters.

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