Soil/Landform Unit 53

Near-level plain south-west of Rokewood

Area:

15 784 ha

1.18% of CMA region

This large unit on a north-west–south-east axis lies just west of Rokewood, bounded by the Western Uplands (sedimentary terrain) in the north-east and

alluvial

valleys and other basaltic plains to the west and south. There is one major and one small occurrence of this unit within the volcanic Western Plains. Unit components include undulating plains, depressions and plains. The soils are alkaline and neutral (strongly

sodic

)

mottled

brown texture contrast soils (

Sodosols

), black in the depressions and some red on the stonier crests. Rainfall decreases from north to south with more cropping further south, as well as broadacre grazing. This unit is susceptible to waterlogging and

compaction

where the landscape is flatter and the lighter upper soil is shallow, and some nutrient decline. Some areas are also susceptible to sheet and rill erosion and structure decline with the strongly sodic subsoils and surface soils.

Gently undulating plain bordering the Woody Yaloak River
	Gentle undulating plain looking across a drainge line of unit 57

Component	1	2	3
Proportion of soil-landform unit	60%	20%	20%
CLIMATE Rainfall (mm)	Annual: 580
Temperature (^oC)	Minimum 8, Maximum 19
Precipitation less than potential evapotranspiration	October-April
GEOLOGY Age and lithology	Quaternary basalt and minor alluvium, Neogene fluvio-marine sand, minor Ordovician marine sandstone
Geomorphology	2.1.4 Dissected Western Uplands associated with volcanic landforms and 6.1.4 Volcanic Western Plains with well developed drainage
LANDUSE	Uncleared areas: Nature conservation Cleared area: Sheep and beef cattle grazing; cropping (cereal); softwood plantations
TOPOGRAPHY Landscape	Gently undulating plains
Elevation range (m)	135-309
Local relief (m)	1-3
Drainage pattern	Dendritic
Drainage density (km/km²)	0.4
Landform	Plains
Landform element	Gently undulating plains	Minor drainage depressions	Level plain
Slope and range (%)	2 (1-4)	1 (0-3)	0 (0-1)
Slope shape	Convex	Straight	Straight
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassy Woodland (0.2%). Plains Grassland/Plains Grassy Woodland Mosaic (0.2%)
SOIL Parent material	Basalt	Basalt and colluvium	Basalt
Description (Corangamite Soil Group)	Alkaline and neutral brown and mottled black texture contrast (36, 35) and minor alkaline red texture contrast soil s(38)	Alkaline and neutral brown texture contrast (36) and mottled black texture contrast soils (35)	Alkaline and neutral brown texture contrast (36) and mottled black texture contrast soils (35)
Soil type sites	MM187, SFS6, MM5075	SFS6, MM5015, SW86	SFS6, MM5015, SW86
Surface texture	Fine sandy clay loam	Fine sandy clay loam	Fine sandy clay loam
Permeability	Low	Low to very low	Low
Depth (m)	<2	>2	<2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Texture contrast soil, moderate to low water holding capacity and nutrient holding capacity in variable depth surface and subsurface soils (gilgai), higher in deep expanisve clay subsoil. Low to moderate permeability. Strongly sodic subsoil. Slow site drainage.	Texture contrast soil, moderate water holding capacity and nutrient holding capacity in varialbe depth surface and subsurface soils (gilgai), higher in deep expanisve clay subsoil. Low permeability. Strongly sodic subsoil. Very slow site drainage. Slight susceptibility to waterlogging and compaction.	Texture contrast soil, moderate to low water holding capacity and nutrient holding capacity in variable depth surfce and subsurface soils (gilgai), higher in deep expanisve clay subsoil. Low permeability. Strongly sodic subsoil. Slow site drainage. Slight susceptibility to waterlogging and compaction.

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