Soil/Landform Unit 180

Productive undulating plains used for seed and pasture production

Area:

8183 ha

0.61% of CMA region

Lying between the basalt plains to the north and dissected ferruginised landscapes to the south, much, if not all, of this flat plain apparently marks the eastern extent of a large former lake in western Victoria. The landscape slopes very gently to the east with increasing dissection as the height above the Barwon River floodplain increases from 10 m to about 40 m. The

lacustrine

deposits appear to be mainly

calcareous

and have formed soils with alkaline reaction trends. Dissolution of calcium carbonate has led to the development of sink holes in some areas, although levelling of paddocks has made these less apparent. The native vegetation has been almost completely removed for agricultural use and its original structure and composition are difficult to determine. In the east there is some evidence of a former woodland, but further west the soils are less well drained and possibly the communities were more stunted.

Maize crop grown for seed production east of Birregurra
	Summer fodder crop

Component	1	2	3
Proportion of soil-landform unit	80%	10%	10%
CLIMATE Rainfall (mm)	Annual: 600–650, lowest January (30), highest February (75)
Temperature (^oC)	Annual: 13, lowest July (8), highest February (19)
Precipitation less than potential evapotranspiration	Temperature: less than 10^oC (av.) June–August Precipitation: less than potential evapotranspiration October–late April
GEOLOGY Age and lithology	Neogene marine marl and calcarenite, and fluvio-marine sand; Recent clay, sand and gravel; Paleogene fluvial sand; minor Quaternary basalt
Geomorphology	6.2.4 Plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Uncleared: Nature conservation; water supply Cleared: Sheep and beef cattle grazing; dairy farming; cropping
TOPOGRAPHY Landscape	Flat plain bordering the present floodplain of the Barwon river
Elevation range (m)	110–130
Local relief (m)	10
Drainage pattern	Dendritic
Drainage density (km/km²)	1.1
Landform	Flat plains
Landform element	Flat plain	Sinkhole	Younger terrace
Slope and range (%)	1 (0–3)	0 (0–1)	2 (1–3)
Slope shape	Linear	Concave	Linear
NATIVE VEGETATION Structure	Woodland	Sedgeland	Woodland
Dominant Species	E. viminalis, E. ovata	Carex spp. Scirpus calocarpus, Schoenus apogon, Juncus spp, Ranunculus spp.	E. ovata, E. camaldulensis
SOIL Parent material	Calcareous clay	Calcareous clay, plant remains	Alluvial clay, silt
Description (Corangamite Soil Group)	Yellow-brown calcareous texture contrast soils, coarse structure (33)	Grey calcareous sodic clay soils (31)	Grey gradational soils (34)
Soil type sites	OTR490, OTR743	CLRA15, CLRA48, SW37	OTR733
Surface texture	Fine sandy loam	Clay	Clay loam
Permeability	Very low	Very low	Very low
Depth (m)	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Dispersible clay subsoils of low permeability are prone to gully and tunnel erosion. Seasonally high watertables lead to soil salting.	High watertables and low permeability lead to waterlogging, soil compaction and soil salting.	High seasonal watertables, low permeability and saline ground water lead to waterlogging, soil compaction and soil salting.

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