Soil/Landform Unit 140

Landform Unit Description

Basalt plain near Shelford

Area:

15 820 ha

1.20% of CMA region

This large single unit lies to the west of Shelford and is bound by basaltic plains to the north, west (Unit

118

) and south (Unit

125

) and a dissected valley to the east (Unit

155

). As part of the volcanic Western Plains, landscape components include plains, very low undulating plains/rises with some stone, and

lunettes

. Little remnant vegetation exists on these cleared plains with less than 0.5% Plains Grassland/Plains Grassy Woodland Mosaic as the only vegetation class. The soils are

mottled

black texture contrast soils (

Sodosols

and

Chromosols

), some strongly

sodic

and some black cracking clays (

Vertosols

) associated with lunettes. Site drainage affects the susceptibility to waterlogging and

compaction

(also dependent on upper soil depth). The degree of sodicity is important to structure decline as well as nutrient availability. This drier area is used for cropping (where minor stone permits) as well as grazing (sheep).

Flat basalt plain
	Basalt plain ready for cropping

Component	1	2	3
Proportion of soil-landform unit	40%	55%	5%
CLIMATE Rainfall (mm)	Annual: 600
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-April
GEOLOGY Age and lithology	Quaternary basalt
Geomorphology	6.1.4 Volcanic Western Plains with well developed drainage
LANDUSE	Uncleared areas: Nature conservation Cleared areas: Sheep and beef cattle grazing; raised bed farming-horticulture; cropping (cereal)
TOPOGRAPHY Landscape	Basalt plains
Elevation range (m)	106-231
Local relief (m)	3
Drainage pattern	Dendritic
Drainage density (km/km²)	0.8
Landform	Plain
Landform element	Plains	Undulating stony rises and plains	Lunette
Slope and range (%)	1 (0-3)	5 (3-10)	4 (2-8)
Slope shape	Straight	Convex	Convex
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland / Plains Grassy Woodland Mosaic (0.4%)
SOIL Parent material	Basalt	Basalt	Aeolian clay, silt and sand
Description (Corangamite Soil Group)	Alkaline black, mottled black and brown texture contrast soils (37/35)	Alkaline black, mottled black and brown texture contrast soils (7/35)	Black cracking clays and alkaline black texture contrast soils (9)
Soil type sites	MM212, CLRA52, SW86, SFS22	MM212, CLRA52, SW85	SW87, SFS21, MM114
Surface texture	Clay loam	Clay loam	Light clay
Permeability	Low to very low	Low	Low
Depth (m)	>2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast soil, low water holding capacity and moderate nutrient holding capacity in often shallow surface and subsurface (gilgai), higher in deep expansive clay subsoil. Low to very low permeability. Sodic, often strongly sodic subsoil, possibly surface soil associated with poor drainage. Slow to very slow site drainage.	Texture contrast soil, low water holding capacity and moderate nutrient holding capacity in often shallow surface and subsurface soils (gilgai), higher in deep expansive clay subsoil. Low permeability. Sodic, often strongly sodic subsoil, possibly surface soil associated with poor drainage, less mottling than plain. Some stone on broad crests. Moderate to slow site drainage.	Expansive clay soil, high to very high low water holding capacity and nutrient holding capacity. Surface and subsurface soils may be self-mulching. Deep sodic or strongly sodic expansive clay subsoil, may be calcareous at depth. Low permeability. Moderate site drainage.

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