Soil/Landform Unit 154

Looking north over the swamps, lunettes and plains of this unit

Area:

1935 ha

0.14% of CMA region

This unit consists of gently undulating plains, level plains swamps and drainage lines that occur near Cressy. Located within the volcanic Western Plains, the relief of this unit is subdued having a masked affect upon agricultural performance and land versatility. This unit has a number of components that are depositional landforms (such as the swamps, level and undulating plains). The unit is adjacent to lakes and basaltic (stony) rises and is found at the head of Lake Corangamite. The remnant vegetation includes less than 1% Plains Grassy Woodland. The soils are black strongly

sodic

texture contrast soils on the plains (coarse structure,

hardsetting

) with black and red cracking

self-mulching

soils on the

lunettes

, and black and grey cracking soils in the swamps. Land use is generally grazing, with the capability of the unit varying with component composition. The shallower soils and strongly structured soils on the lunettes provide more use throughout the year than the wetter flats.

Lower plains and swamps line the southern boundary of this unit
	The broad plains are mainly used for grazing

Component	1	2	3
Proportion of soil-landform unit	40%	55%	5%
CLIMATE Rainfall (mm)	Annual: 560
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Recent clay, sand and gravel, basalt and minor coastal sand dunes
Geomorphology	6.1.5 Alluvium, terraces, floodplains, lakes, swamps and lunettes of the Volcanic Western Plains
LANDUSE	Uncleared: Nature conservation; water supply Cleared: Cropping; beef cattle and sheep grazing; dairy
TOPOGRAPHY Landscape	Gently undulating broad plains
Elevation range (m)	119-140
Local relief (m)	2
Drainage pattern	Centripetal
Drainage density (km/km²)	1.3
Landform	Plains
Landform element	Gently undulating plains	Level plains	Stream chennels
Slope and range (%)	1 (0-5)	1 (0-3)	4 (1-8)
Slope shape	Linear	Linear	Linear
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (1%)
SOIL Parent material	In situ basalt and associated colluvium	In situ basalt and associated colluvium	Alluvial clay, silt and sand
Description (Corangamite Soil Group)	Alkaline mottled black texture contrat soils, some not mottled (35)	Alkaline mottled black texture contrast soils, some not mottled (35)	Alkaline grey and black cracking clays (31)
Soil type sites	SW86, CLRA49, SW90	SW86, CLRA49, SW90	SW37, CLRA48, CLRA15
Surface texture	Fine sandy clay loam	Fine sandy clay loam	Medium clay
Permeability	Low	Low	Very low
qDepth (m)	<2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast, possible surface waterlogging and compaction. Sodic subsoil, possibly the surface soil as well (structure decline).	Texture contrast, possible surface waterlogging and compaction. Sodic subsoils, possibly the surface soil as well (structure decline).	High seasonal watertable leads to soil compaction. High organic matter content, high clay content and expansive clays. May be better drained where lighter soil occurs.

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