Soil/Landform Unit 117

Broad basaltic plains with broadly defined drainage flats and depressions

Area:

61 965 ha

4.64% of CMA region

This unit of undulating basaltic plains has poorly developed drainage and

and lies within the volcanic Western Plains. This very large unit on a north-west–south-east axis extends from Wallindoc in the north, through Cressy and south to Winchelsea. Unit components include stony undulating plain/rises, plains and minor depressions. The remnant native vegetation class is Plains Grassland/Plains Grassy Woodland Mosaic. The soils are alkaline (strongly

sodic

)

mottled

black texture contrast soils (

Sodosols

), with some gradational soils (

Dermosols

) on the stonier (and shallower) rises. Rainfall decreases from north to south with more broadacre grazing and cropping further south. This unit is susceptible to waterlogging and (

compaction

where the lighter upper soil is shallow) and some nutrient decline. Some areas are also susceptible to sheet and rill erosion and structure decline with the strongly sodic subsoils and surface soils.

Fodder crop on gently undulting plains near Wilgul
	Cleared plains near Wilgul. The little basalt rock that occurs on these plains hs been cleared into heaps

Component	1	2	3
Proportion of soil-landform unit	55%	35%	10%
CLIMATE Rainfall (mm)	Annual: 600
Temperature (^oC)	Minimum 9, Maximum 19
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Quaternary basalt and minor alluvium
Geomorphology	6.1.3 Volcanic Western Plains with poorly developed drainage
LANDUSE	Uncleared areas: Nature conservation Cleared areas: Sheep and beef cattle grazing; cropping (cereal); softwood plantations
TOPOGRAPHY Landscape	Gently undulating basalt plains
Elevation range (m)	70-223
Local relief (m)	50
Drainage pattern	Centripetal
Drainage density (km/km²)	0.5
Landform	Plain
Landform element	Undulating stony rise	Plains	Depressions
Slope and range (%)	2 (1-8)	1 (0-3)	2 (1-3)
Slope shape	Convex	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland/Plains Grassy Woodland Mosaic (0.2%)
SOIL Parent material	Basalt	Basalt and colluvium	Basalt, colluvium and alluvium
Description (Corangamite Soil Group)	Alkaline mottled black texture contrast soils (35) and shallow friable loams (40)	Alkaline mottled black texture contrast soils (35)	Grey and black cracking clays (39)
Soil type sites	SW86, CLRA49, SW26	SFS20, MM110, SW86	SW88, SFS2, SW89
Surface texture	Fine sandy clay loam	Fine sandy clay loam	Light clay
Permeability	Moderate to low	Low	Very low
Depth (m)	<2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast soil, moderate water holding capacity and nutrient holding capacity in variable depth surfae and subsurface soils (gilgai), higher in deep expansive clay subsoil. High (loams) to low permeability. Sodic, often strongly sodic subsoil. Some stone on broad crests/rises. Moderate to slow site drainage.	Texture contrast soil; moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability and sodic (often strongly) subsoil. Slow site drainage.	Uniform expansive clay soil, high to very high water holding capacity and nutrient holding capacity. Cracking soil, black soil may have self-mulching surfaces. Low permeability once moist; sodic (often strongly) subsoil. Slow to very slow site drainage.

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