Soil/Landform Unit 171

Long gentle slopes of the remnant ferruginised plateau

Area:

14 742 ha

1.10% of CMA region

Between the ferruginised plateau of soillandform unit 79 and the basaltic plains, a long narrow plain extends from the Barwon River near Winchelsea to the middle reaches of Thompson Creek. Deeply weathered texture contrast soils are found on most of this unit, with occasional areas of aeolian sand. Remnants of woodlands and open forests are found along many reserves with the unusual occurrence of

Eucalyptus pauciflora

on many of the better drained and less fertile sites. Most areas have been cleared for agriculture and, despite the fairly low rainfall, dairy farming is common. Other uses include sheep and beef cattle grazing and cereal cropping. Soil salting is a problem in many areas and some minor gully erosion has also occurred.

Drainage line of the Merrigig Creek with a planting of natives. Salinity was evident in this depression
	Undulating plains are mainly used for grazing by sheep and beef cattle

Component	1	2	3	4	5
Proportion of soil-landform unit	35%	20%	10%	15%	10%
CLIMATE Rainfall (mm)	Annual: 600-650, lowest January (30), highest August (65)
Temperature (^oC)	Annual: 13, lowest July (9), highest February (19)
Seasonal growth limitations	Temperature: less than 10^oC (av.) June-July Precipitation: less than potential evapotranspiration October-mid April
GEOLOGY Age and lithology	Neogene fluvio-marine sand and minor Recent clay, sand and gravel; Neogene marine marl and Paleogene fluvial sand
Geomorphology	6.2.4 Plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Cleared areas: Dairy and beef cattle grazing on mainly improved pastures; cereal cropping; some sand extraction
TOPOGRAPHY Landscape	Gently undulating plain lying between basalt to the north and lateritic plateaux to the south
Elevation range (m)	40-130
Local relief (m)	20
Drainage pattern	Dendritic
Drainage density (km/km²)	1.6
Landform	Gentle rises				Valley floors
Landform element	Crest and upper slope	Middle slope	Crest and slope	Lower slope
Slope and range (%)	3 (0-11)	4 (1-7)	5 (2-10)	4 (0-7)	1 (0-2)
Slope shape	Convex	Linear	Irregular	Convex	Concabe
NATIVE VEGETATION Structure	Open forest	Woodland	Low woodland	Woodland	Woodland
Dominant species	E. viminalis, E. ovata, E. pauciflora, Acacia melanoxylon	E. viminalis, E. ovata, Casuarina stricta, C. littoralis	E. viminalis, E. obliqua	E. ovata, E. viminalis, Casuarina stricta	E. camaldulensis, E. viminalis, Acacia melanoxylon
SOIL Parent material	Sandy clay	Sandy clay	Siliceous sand	Sandy clay	Sand, silt and clay
Description (Corangamite Soil Group)	Mottled brown, grey, yellow and red texture contrast soils (13)	Yellow-brown sodic texture contrast soils, coarse structure (14)	Grey sand soils (11)	Brown, grey or yellow sodic texture contrast soils (19)	Brown gradational soils (34)
Soil type sites	OTR492, OTR744	OTR606	OTR742	OTR734	OTR414, OTR416, OTR748
Surface texture	Sandy loam	Fine sandy loam	Loamy sand	Sandy loam	Fine sandy loam
Permeability	Moderate	Low	Very high	Moderate	High
Depth (m)	>2	>2	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Low inherent fertility, phosphorus fixation and leaching of permeable A horizons lead to nutrient decline.	Dispersible subsoils are prone to gully erosion and slumping of road batters.	Low inherent fertility and high permeability lead to nutrient decline. Weakly structured surfaces with low water holding capacity are prone to wind erosion.	Sodic subsoils with high seasonal watertables are prone to soil salting. Dispersible subsoils are prone to gully erosion.	Seasonal saline watertable development leads to soil salting. Rapid surface runoff from adjacent areas leads to scouring and gully erosion. Weakly structured surface soils in poorly drained areas are prone to compaction.

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