Soil/Landform Unit 137

The gently undulating plains have dark texture contrast soils on slopes with poorly drained soils in depressions. Stones are common on some slopes

Area:

4810 ha

0.36% of CMA region

This gently undulating plains unit (part of the volcanic Western Plains) has well developed drainage and deep

regolith

. This unit of basaltic and sedimentary plains is dominated by one large occurrence just north of Camperdown extending to the western boundary of the catchment. Eruption point complexes (Units

110

107

) are to the south, and a lake and stony rises complex (Unit

112

) to the north. Unit components include very low rises as well as plains with remnant Plains Grassy Woodland. The soils are black texture contrast soils (

Chromosols

) and are strongly

sodic

on the basalt (

Sodosols

). Some of these soils may have

friable

surface soils; however, lighter surface textures are more prone to nutrient decline and sheet erosion on the slopes, while the plains and depressions are more susceptible to waterlogging. Rainfall is sufficient to promote intensive grazing (mainly for dairying) and minor cropping.

Gently undulating plains with annual pastures near Kariah

Component	1	2	3	4
Proportion of soil-landform unit	20%	25%	50%	5%
CLIMATE Rainfall (mm)	Annual: 750
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	November-March
GEOLOGY Age and lithology	Neogene fluvial and marine gravel, sand, silt and clay, Quaternary basalt and scoria deposits
Geomorphology	6.1.4 Volcanic Western Plains with well developed drainage
LANDUSE	Uncleared: Nature conservation Cleared: Beef cattle and sheep grazing; dairy farming; cropping (ceral and summer fodder)
TOPOGRAPHY Landscape	Undulating basalt plains
Elevation range (m)	140-220
Local relief (m)	3-5
Drainage pattern	Parallel
Drainage density (km/km²)	1.3
Landform	Gently undulating plains			Drainage depressions
Landform element	Broad crest	Slopes	Plains	Drainage lines
Slope and range (%)	2 (0-5)	5 (3-10)	2 (1-3)	2 (0-3)
Slope shape	Convex	Convex	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (3.1%)
SOIL Parent material	Sand, silt and clay; basalt	Sand, silt and clay; basalt	Sand, silt and clay; basalt	Alluvial sand, silt and clay
Description (Corangamite Soil Group)	Neutral mottled black texture contrast soils (13/35)	Neutral mottled black texture contrast soils (13/35)	Neutral mottled black texture contrast soils (13/35)	Alkaline black texture contrast soils (32)
Soil type sites	SW67, CLRA36, SW86	SW67, CLRA36, SW86	SW67, CLRA36, SW86	SFS20, SW88, SW95
Surface texture	Loamy sand; fine sandy loam	Loamy sand; fine sandy loam	Loamy sand; fine sandy loam	Fine sandy loam
Permeability	Low to moderate	Low to moderately high	Low to moderate	Low
Depth (m)	<2	<2	<2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast, low to moderate water holding capacity and nutrient holding capacity depending on depth and stoniness in upper soil, high in subsoil. Non-sodic (moderate structure) and strongly sodic (coarse structure) subsoils. Moderate site drainage. Some susceptibility to nutrient decline and sheet and rill erosion.	Texture contrast, low to moderate water holding capacity and nutrient holding capacity depending on depth and stoniness in upper soil, high in subsoil. Non-sodic (moderate structure) and strongly sodic (coarse structure) subsoils. Moderate site drainage. Some susceptibility to nutrient decline and sheet and rill erosion.	Texture contrast, low to moderate water holding capacity and nutrient holding capacity depending on depth and stoniness in upper soil, high in subsoil. Non-sodic (moderate structure) and strongly sodic (coarse structure) subsoils. Slow to moderate site drainage. Some susceptibility to nutrient decline and sheet and rill erosion.	Texture contrast, low to moderate water holding capacity and nutrient holding capacity depending on depth and stoniness in upper soil, high in subsoil. Non-sodic (moderate structure) and strongly sodic (coarse structure) subsoils. Very slow site drainage. Some susceptibility to waterlogging and nutrient decline.

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