Soil/Landform Unit 121

Looking north over the vast broad plains. There is considerable variation of soils and landforms within this large unit

Area:

16 640 ha

1.25% of CMA region

The undulating rises with broad areas of near level plains extend from Anakie to Geelong. These areas are volcanic in origin and have shallow

regolith

development for basalts across the Western Plains. The thin soils support grazing and minor cropping with an average annual rainfall of 540 mm. Vegetation is limited to Plains Grassland. The co-dominant soils of the rises, which have variable amounts of surface stone, are alkaline

mottled

black texture contrast soils. There are minor occurrences of neutral,

friable

brown gradational soils, particularly on the rises with many surface stones, and alkaline mottled brown and mottled brown, grey or yellow texture contrast soils. On the level plains the co-dominant soils are also alkaline, mottled black texture contrast/cracking clay soils, with minor occurrences of alkaline red mottled brown and mottled yellow texture contrast soils. Alkaline grey cracking clays occur in depressions on the plain and shallow black cracking clays occur on the escarpment bordering Unit

119

. The texture contrast soils have a moderate to high nutrient holding capacity in the topsoil, and moderate water holding capacity in deep topsoils. Well structured subsoils represent moderate to rapid site drainage. Soils are prone to sheet and rill erosion, and gully erosion where

sodic

subsoils are exposed.

Land use is restricted to grazing across much of the unit due to the high frequency of surface stones
	Broad plains with surface stones

Component	1	2	3	4
Proportion of soil-landform unit	20%	20%	55%	5%
CLIMATE Rainfall (mm)	Annual: 540
Temperature (^oC)	Minimum 9, Maximum 20
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: Nature conservation Cleared: Sheep and beef cattle grazing; cropping (cereal)
TOPOGRAPHY Landscape	Undulating rises and broad plains
Elevation range (m)	11-220
Local relief (m)	2-3
Drainage pattern	Dendritic
Drainage density (km/km²)	0.8
Landform	Gentle rises		Broad plains	Open depression/drainage line
Landform element	Broad gentle crests and upper slopes	Lower slopes	Plains
Slope and range (%)	3 (1-7)	2 (1-4)	0 (0-1)	3 (1-5)
Slope shape	Convex	Linear	Linear	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland (0.4%)
SOIL Parent material	In situ basalt	In situ basalt and colluvium	In situ basalt and colluvium	In situ basalt and colluvium
Description (Corangamite Soil Group)	Alakline mottled black texture contrast soils (35) and neutral brown gradational soils (41)	Alkaline mottled black texture contrast soils (35), alkaline mottled brown, grey or yellow texture contrast soils (36)	Alkaline mottled black texture contrast soils (35), black, grey or red cracking clays (39)	Alkaline black texture contrast soils (35) and grey cracking clays (39)
Soil type sites	SW86, SW8, SW96	SW99, SW97	MM5028, SW102, SW100	SW86, SW101, SW99
Surface texture	Fine sandy clay loam, clay loam	Fine sandy clay loam	Fine sandy clay loam	Fine sandy clay loam
Permeability	High to moderate	Moderate	Low to moderate	Very low
Depth (m)	<0.7	<1.5	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast and gradational. Stony. Moderate to high nutrient capacity in upper soil, high in subsoil. Low water holding capacity, shallow soil. Structured soil and moderately rapid site drainage, moderate to high permeability. Texture contrast soils are sodic, expansive clay subsoils.	Texture contrast, often stony. Moderate to high nutrient holding capacity in upper soil, high in subsoil. Moderate water holding capacity, moderately deep soil. Structured soil and moderately rapid site drainage, moderate permeability. Strongly sodic in subsoil, also expansive clays.	Texture contrast, often stony. Moderate to high nutrient holding capacity in upper soil, high in subsoil. Moderate water holding capacity, moderate deep soil. Structured soil and moderately rapid site drainage, moderate permeability. Strongly sodic in subsoil, also expansive clays.	Texture contrast or uniform, occasionally stony. Moderate to high nutrient holding capacity in upper soil, high in subsoil. Moderate to high water holding capacity, moderately deep to deep soil. Very low permeability. Strongly sodic in subsoil. Expansive clay soils, very slow site drainage.

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