Soil/Landform Unit 187

Gently undulating rises south-west of Irrewillipe support a wide range of land uses including softwood and hardwood plantations

Area:

3873 ha

0.29% of CMA region

Gently undulating rises on sedimentary origin occur between Irrewillipe and Simpson. These rises comprise a variety of vegetation classes including Lowland Forest and Herb-rich Foothill Forest.

The gentle slopes have low nutrient and water holding capacities in the subsurface and subsoil. Heavy, possibly expansive clay subsoil is often

massively

structured, therefore indicating very low soil permeabilities. The forests have historically provided sawn timber, posts and firewood and is still used for softwood plantations. Dairy farming in this area is the prominent land use due to the sufficiently high annual rainfall (950 mm). Soils include

acidic

mottled

duplex

soils with massive and structured subsoils. Sandy mottled duplex soils with massive and structured subsoils may also occur.

Red soils of the dam bank are indicative of the ferruginised nature of crests and upper slopes
	Gentle slopes of the sedimentary rises has hardsetting duplex soils that are prone to sheet and rill erosion

Component	1	2	3	4
Proportion of soil-landform unit	50%	36%	12%	2%
CLIMATE Rainfall (mm)	Annual: 950
Temperature (^oC)	Minimum 8 , Maximum 18
Precipitation less than potential evapotranspiration	November–March
GEOLOGY Age and lithology	Neogene fluvio-marine sand, silt and clay
Geomorphology	6.2.4 Plains, rises and low hills of the Sedimentary Western Plains
LANDUSE	Uncleared: Hardwood forestry for sawlogs, posts and poles; softwood plantations; nature conservation; water supply Cleared: Dairy farming; beef cattle and sheep grazing; water supply; softwood plantation
TOPOGRAPHY Landscape	Gently undulating rises
Elevation range (m)	126–202
Local relief (m)	30
Drainage pattern	Dendritic
Drainage density (km/km²)	1.2
Landform	Rises			Drainage depressions
Landform element	Broad low crests and upper slopes	Mid slopes	Lower slopes
Slope and range (%)	4 (1–12)	2 (1–5)	3 (1–6)	4 (0–7)
Slope shape	Convex	Straight	Concave	Concave
NATIVE VEGETATION Ecological Vegetation Class	Lowland Forest (14.9%), Herb-rich Foothill Forest (3.2%)
SOIL Parent material	Sand, silt and clay	Sand, silt and clay	Sand, silt and clay	Colluvium and alluvium; sand, silt and clay
Description (Corangamite Soil Group)	Acidic, mottled yellow texture contrast soils (13)	Acidic, mottled yellow texture contrast soils (13)	Acidic, mottled yellow texture contrast soils (13)	Acidic, mottled black, brown, grey or yellow texture contrast soils (13/33)
Soil type sites	SW42, SW67, OTR601	SW42, SW67, OTR601	SW42, SW67, OTR601	SW42, OTR601, SW2
Surface texture	Fine sandy loam	Fine sandy loam	Fine sandy loam	Fine sandy loam
Permeability	Moderate	Moderate	Moderate to low	Low
Depth (m)	<2	<2	<2	<2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Large texture contrast, low nutrient holding capacity and water holding capacity in subsurface and surface soil, higher in subsoil. Acidic (not quite strongly). Heavy, possibly expansive clay subsoil. Moderately rapid site drainage.	Large texture contrast, low nutrient holding capacity and water holding capacity in subsurface and surface soil, higher in subsoil. Acidic (not quite strongly). Heavy, possibly expansive clay subsoil. Moderately rapid site drainage.	Large texture contrast, low nutrient holding capacity and water holding capacity in subsurface and surface soil, higher in subsoil. Acidic (not quite strongly). Heavy, possibly expansive clay subsoil. Slow site drainage, higher susceptibility to waterlogging and compaction compared with Component 1.	Texture contrast, low nutrient holding capacity and water holding capacity in subsurface and surface soil, higher in subsoil. Acidic (not quite strongly). Heavy, possibly expansive clay subsoil. Slow site drainage, susceptibility to waterlogging and compaction.

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