Soil/Landform Unit 36

The gently inclined low cone of Mount Widderin

Area:

995 ha

0.07% of CMA region

The gently inclined slopes of low cones in the Cargerie area and Mount Widderin are derived from volcanic scoria, tuff and basalt. These volcanic eruption points on the Western Plains have nearly 60 m of local relief and are some of the most northerly cones on the Western Plains. The cones have been extensively cleared with little remnant vegetation (Plains Grassy Woodland - 0.2%) occurring as sporadic stands across the landscape and roadside reserves. Slopes have highly fertile loamy soils that have been used for grazing mainly due to the abundance of surface stone that limits cultivation. The basaltic rock, scoria and tuff support shallow red and black

friable

loamy soils, with the lower slopes supporting fewer surface stones and

mottled

texture contrast soils.

Hardsetting

surfaces, slowly permeable subsoils, and significant overland flow result in minor sheet and rill erosion. Periodic waterlogging also occurs in wet seasons. Areas with shallow stony gradational soils are susceptible to leaching of nutrients, and

compaction

is a problem on the lower slopes and flats.

The surrounding plains are mainly used for croping while the slopes of the low cones are mainly used for grazing

Component	1	2	3	4
Proportion of soil-landform unit	80%	2%	1%	17%
CLIMATE Rainfall (mm)	Annual: 690
Temperature (^oC)	Minimum 7, Maximum 18
Precipitation less than potential evapotranspiration	October-March
GEOLOGY Age and lithology	Pleistocene; basalt, scoria tuff
Geomorphology	6.1.1 Eruption points of the Volcanic Western Plains and 2.1.4 Dissected Weatern Uplands associated with volcanic landforms
LANDUSE	Uncleared: Nature conservation; forest grazing Cleared: Beef cattle and sheep grazing; cropping (cereal)
TOPOGRAPHY Landscape	Low cone and gently inclined slopes
Elevation range (m)	280-411
Local relief (m)	60
Drainage pattern	Radial and shut flow (poorly developed channels)
Drainage density (km/km²)	<0.1
Landform	Depressions			Volcanic cone
Landform element	Long gentle upper slopes	Depression	Stony rise	Slope and crest
Slope and range (%)	2 (1-3)	1 (1-2)	3 (2-5)	25 (5-40)
Slope shape	Straight	Straight	Convex	Straight
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (0.2%)
Dominant species	E. ovata, E. viminalis, E. Rubida, E. obliqua			E. viminalis, E. radiata
SOIL Parent material	In situ weathered basalt and scoria	Alluvium	In situ weathered basalt and scoria	In situ weathered basalt and scoria
Description (Corangamite Soil Group)	Mottled yellow, grey sodic texture contrast soil, coarse structure (35)	Black cracking clay soil, coarse structure (31)	Red shallow, stony gradational soil (40)	Stony red gradational soil (40)
Soil type sites	MM109, SW86, CLRA49	SW37, CLRA15, CLRA48	SW96, SW26, BD5	SW96, SW26, BD5
Surface texture	Clay loam	Clay	Clay loam	Clay loam
Permeability	Moderate to low	Moderate	High	High
Depth (m)	1.5	1.5	0.5	1
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Hardsetting surfaces and slowly permeable subsoils result in significant overland flow. Sheet and rill erosion also occur from this overland flow. Soil compaction is also a limitation for soils with shallow topsoils. Periodic waterlogging also occurs.	Clay soils beside creeks are prone to periodic waterlogging. Streambank undercutting and streambank erosion is common. Slowly permeable subsoils are also quite sodic and prone to gully erosion.	Overland flow, nutrient leaching and decline all reflect highly permeable soils. Sheet erosion is common with excessive rainfall events.	Steep slopes and hardsetting surfaces result in significant overland flow. Sheet and rill erosion also occur from this overland flow.

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