Soil/Landform Unit 116

Soils of the gentle low hills between Colac and Winchelsea are mainly used for grazing and cropping

Area:

457 ha

0.03% of CMA region

The undulating low hills east of Colac are derived from basalt that has little regolith development. As part of the Western Plains, these low hills are visible from the Princes Highway when heading to Winchelsea from Colac. The local relief of these hills is nearly 35 m. The low hills have little remnant vegetation (less than 1%) with the major vegetation class being Plains Grassy Woodland. The hills have slopes and footslopes that have been used for cereal production and grazing (beef cattle). The basaltic rock supports

mottled

yellow and black texture contrast soils. Surface stones are mainly confined to the crest and upper slopes, though basalt floaters can make cultivation difficult on steeper slopes. Nutrient decline is a minor degradation issue of these low hills.

Slopes of the low hills are long and gentle with no remnant vegetation remaining

Component	1	2	3
Proportion of soil-landform unit	10%	65%	25%
CLIMATE Rainfall (mm)	Annual: 720
Temperature (^oC)	Minimum 9, Maximum 19
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Quaternary basalt
Geomorphology	6.1.3 Volcanic Western Plains with poorly developed drainage
LANDUSE	Uncleared areas: Nature conservation Cleared areas: Beef cattle grazing; cropping (cereal)
TOPOGRAPHY Landscape	Undulating low basalt hills
Elevation range (m)	110-160
Local relief (m)	32
Drainage pattern	Dendritic
Drainage density (km/km²)	0.3
Landform	Low gentle hills
Landform element	Crest	Hillslope	Footslope
Slope and range (%)	4 (1-7)	7 (3-10)	5 (2-9)
Slope shape	Convex	Convex	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (0.8%)
SOIL Parent material	Basalt	Basalt	Basalt
Description (Corangamite Soil Group)	Alkaline mottled black (35) and mottled yellow or brown texture contrast soils (37)	Alkaline mottled black and mottled yellow or brown texture contrast soils (35)	Alkaline mottled black and mottled brown, grey or yellow texture contrast soils (35)
Soil type sites	SW86, SFS20, SFS5b	SW86, SFS20, CLRA49	SW86, SFS20, CLRA49
Surface texture	Fine sandy clay loam	Fine sandy clay loam	Fine sandy clay loam
Permeability	Low	Low	Very low
Depth (m)	<1	1-2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast, moderate to high water holding capacity and nutrient holding capacity depending on depth and stoniness. Strongly sodic soils with coarse structure, hardsetting. Minor non-sodic soils with medium structure. Moderately rapid site drainage. Some susceptibility to sheet and rill erosion.	Texture contrast, moderate to high water holding capacity and nutrient holding capacity depening on depth and stoniness. Strongly sodic soils with coarse structure, hardsetting. Moderately rapid site drainage. Some susceptibility to sheet and rill erosion.	Texture contrast, moderate to high water holding capacity and nutrient holding capacity depening on depth and stoniness. Strongly sodic soils with coarse structure, hardsetting. Moderately rapid site drainage. Some susceptibility to sheet and rill erosion.

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