Soil/Landform Unit 46

Undulating plains and rises east of Mount Mercer

Area:

5168 ha

0.39% of CMA region

This unit of undulating basaltic rises is a volcanic landform within the dissected Western Uplands. This unit is on the boundary of the uplands, centred on Mount Mercer, with basaltic plains to the south (Unit

118

) and young and old sedimentary rises to the north (Units

and

). Unit components include crests, upper slopes, mid and lower slopes, plains and minor depressions. The soils are alkaline (strongly sodic) mottled black texture contrast soils (Sodosols) and some gradational soils (Dermosols) on the stonier (and shallower) rises. Annual rainfall is greater than on units to the south, with land use predominantly broadacre grazing. 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.

Looking across the rises and plain towards Mount Mercer
	Grazing is the main land use of these volcanic plains

Component	1	2	3	4
Proportion of soil-landform unit	15%	55%	28%	2%
CLIMATE Rainfall (mm)	Annual: 690
Temperature (^oC)	Minimum 7, Maximum 18
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Quaternary basalt, Ordovician marine sandstone and shale, Recent clay, sand and gravel
Geomorphology	2.1.4 Dissected Western Uplands associated with volcanic landforms
LANDUSE	Uncleared areas: Nature conservation Cleared: Sheep and beef cattle grazing; cropping (cereal); softwood plantations
TOPOGRAPHY Landscape	Undulating low basalt hills
Elevation range (m)	196-395
Local relief (m)	60
Drainage pattern	Dendritic
Drainage density (km/km²)	1.1
Landform	Hillslopes		Flat	Drainage depressions
Landform element	Broad crest and upper slopes	Mid and lower slopes	Plain	Drainage lines
Slope and range (%)	3 (1-8)	3 (2-6)	1 (0-2)	1 (0-4)
Slope shape	Convex	Linear/Concave	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland/Plains Grassy Woodland Mosaoic (0.7%), Valley Grassy Forest (0.2%), Heathy Dry Forest (0.1%)
SOIL Parent material	Basalt	Basalt and colluvium	Basalt and colluvium	Basalt, colluvium and alluvium
Description (Corangamite Soil Group)	Shallow stony black friable loams (40/35)	Alkaline mottled black texture contrast soils (35)	Alkaline mottled black texture contrast soils (35)	Alkaline mottled black texture contrast soils (35)
Soil type sites	SW96, SW86, CLRA49	SW86, CLRA49, SW90	SW86, CLRA49, SW90	SW86, CLRA49, SW90
Surface texture	Loam	Clay loam	Clay loam	Clay loam
Permeability	Moderate	Low	Low	Very low
Depth (m)	<1.5	<2	<2	<2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast and loam soils with moderate water holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. High (loams to low permeability). Generally, strongly sodic subsoil. Some stone on broad crests/rises. Moderate site drainage.	Texture contrast soil with moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability. Generally, strongly sodic subsoil. Minor stone. Moderate site drainage.	Texture contrast soil with moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability. Generally, strongly sodic subsoil. Minor stone. Slow site drainage.	Texture contrst soil with moderate water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expanisve clay subsoil. Low permeability. Generally, strongly sodic subsoil. Very slow site drainage.

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