Soil/Landform Unit - Murtoa flats

Alluvial plain east of Murtoa used for crops and remnant black box vegetation

Area: 844 ha

0.04% of CMA region

Drainage/depositional entities near Murtoa form part of an extensive plains complex. This drainage unit is part of the clay plains with subdued ridges geomorphological unit (5.4). These low

alluvial

depressions and flats of

Quaternary

sediments are generally aligned north-south and lie just to the north of the Wimmera River alluvial plains, draining into Corkers Creek to the south. Dominated by the flats and drainage depressions, drainage is extensive away from the main drainage lines and depressions. Site drainage is generally very slow with soils including grey cracking clay soils (

Vertosols

), occasionally with pedal (structured) and

self-mulching

surfaces. Often

hardsetting

or cracking,

gilgai

micro relief is likely and generally topsoil depth is shallow. Seasonal inundation and waterlogging can occur.

Compaction

is also a susceptibility factor with these soils and topography. Broadacre dryland cropping is the major enterprise with minor grazing (sheep). The four main vegetation communities found are Riverine Chenopod Woodland, Lignum Wetland, Plains Grassland and Plains Savannah.

Alluvial plain crop and remnant vegetation along fenceline
	Black box flats

Component	1	2	3	4
Proportion of soil-landform unit	10%	15%	65%	10%
CLIMATE Rainfall (mm)	Annual: 440
CLIMATE Rainfall (mm)	Annual: 440
Temperature (^oC)	Minimum 8, Maximum 21
Precipitation less than potential evapotranspiration	September–April
GEOLOGY Age and lithology	Neogene marine sand and silt (Parilla Sand); Quaternary fluvial silt, sand and minor gravel (Shepparton Formation)
GEOLOGY Age and lithology
Geomorphology	4.2. Plains with leveed channels of the older alluvial plains
LANDUSE	Uncleared areas: nature conservation Cleared areas: dryland cropping; sheep and beef cattle grazing
LANDUSE
TOPOGRAPHY Landscape	Subdued depression of older plain
TOPOGRAPHY Landscape	Subdued depression of older plain
Elevation range (m)	129–138
Local relief (m)	2
Drainage pattern	Dendritic
Drainage density (km/km²)	0.8
Landform	Gentle side slopes		Alluvial plains
Landform element	Upper slope	Long gentle lower slope	Flat and drainage depression	Drainage line
Slope and range (%)	3 (1-8)	2 (1-3)	1 (0-2)	0 (0-1)
Slope shape	Convex	Linear	Straight	Concave
NATIVE VEGETATION Ecological Vegetation Class	Plains Grassland (37.5%), Lignum Wetland (30.0%), Riverine Chenopod Woodland (12.8%), Other (2.6%)
NATIVE VEGETATION Ecological Vegetation Class
SOIL Parent material	Marine sand and silt	Marine sand and silt	Fluvial gravel, sand and silt	Alluvial gravel, sand and silt
SOIL Parent material	Marine sand and silt	Marine sand and silt	Fluvial gravel, sand and silt	Alluvial gravel, sand and silt
Description (Corangamite Soil Group)	Cracking and self-mulching clay soils (24) and sodic red texture contrast soils (25)	Cracking and self-mulching clay soils (24) and sodic red texture contrast soils (25)	Cracking and self-mulching clay soils (24)	Cracking and self-mulching clay soils (24)
Soil type sites	WIA10, WIA19, WIA16	WIA10, WIA19, WIA16	WIA10, WIA19, WIA33	WIA10, WIA19, WIA33
Surface texture	Fine sandy loam to medium clay	Fine sandy loam to medium clay	Medium clay	Medium clay
Permeability	Moderate to slow	Slow	Slow	Very slow
Depth (m)	1.5	> 2	> 3	> 3
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS Critical land features, processes, forms	Hardsetting soil slightly susceptible to sheet and rill erosion. Soils are prone to compaction at critical moisture contents. Subsoil susceptible to gully erosion when exposed due to dispersive (sodic) nature. Slight susceptibility to acidification of surface soil.	Soils may be slightly susceptible to inundation and waterlogging where sandy surface soil is shallow. Hardsetting soil slightly susceptible to sheet and rill erosion. Soils are prone to compaction at critical moisture contents. Subsoil susceptible to gully erosion when exposed due to dispersive (sodic) nature. Slight susceptibility to acidification of surface soil.	Flats and drainage depressions susceptible to inundation and waterlogging, but can be variable due to micro relief (gilgai) and surface condition (self-mulching or epipedal). Surface soils friable and only slightly susceptible to wind erosion. Soils may be susceptible to compaction at critical moisture contents.	Drainage lines susceptible to inundation and waterlogging, especially from extensive flood events. Surface soils tend to be epipedal (massive) and only slightly susceptible to wind erosion. Soils may be susceptible to compaction at critical moisture contents.

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