Soil/Landform Unit - Lorquon undulating plains

Lorquon plains north of Nhill

Area: 78 392 ha

3.34% of CMA region

Gently undulating plains north of the Little Desert and south of the Big Desert include a complex of plains and low gentle terrain between NNW-SSE trending rises and low hills. Slopes are generally less that 3% with parent material largely a combination of

fluvial

and

aeolian

deposits. Uniform grey and brown clays (

Vertosols

) predominate with

sodic

red, brown, yellow and grey texture contrast soils (

Sodosols

) found mainly in higher topographic positions than those of the clays. The clays may experience periodic waterlogging in lower areas during wet seasons but this is relatively infrequent. All soils may be susceptible to

compaction

at critical moisture contents. Cereal cropping and grazing are major land uses. Plains Savannah and Ridged Plains Mallee are the most expansive remnant vegetation communities. Areas of other vegetation communities such as Lignum Swampy Woodland, Plains Woodland, Sandstone Ridge Shrubland, Shallow Sands Woodland, Parilla Mallee, Low Rises Woodland and Heathy Mallee are also found.

Cultivated plains with a stranded beach ridge rise in the distance
	Cultivated paddock near Lawloit

Component	1	2	3
Proportion of soil-landform unit	5%	80%	15%
CLIMATE Rainfall (mm)	Annual: 430
CLIMATE Rainfall (mm)	Annual: 430
Temperature (^oC)	Minimum 8, Maximum 22
Precipitation less than potential evapotranspiration	September–April
GEOLOGY Age and lithology	Quaternary paludal silt and clay; Quaternary aeolian dune sand (Lowan Sand); Neogene marine sand and silt (Parilla Sand)
GEOLOGY Age and lithology
Geomorphology	5.5.1 Prominent ridges and oriented swales of the North Western Dunefields and Plains
LANDUSE	Uncleared areas: nature conservation Cleared areas: dryland cropping; sheep grazing
LANDUSE
TOPOGRAPHY Landscape	Gently undulating plains
TOPOGRAPHY Landscape	Gently undulating plains
Elevation range (m)	99–179
Local relief (m)	1–2
Drainage pattern	Dendritic
Drainage density (km/km²)	0.1
Landform	Gently undulating plains
Landform element	Low rise crest	Broad gentle plain	Low rise slope
Slope and range (%)	4 (1-7)	1 (0-2)	3 (2-7)
Slope shape	Convex	Straight	Linear
NATIVE VEGETATION Ecological Vegetation Class	Ridged Plains Mallee (27.5%), Plains Savannah (25.3%), Low Rises Woodland (17.3%), Plains Woodland (10.5%), Other (17.2%)
NATIVE VEGETATION Ecological Vegetation Class
SOIL Parent material	Marine sand and silt, aeolian sand	Paludal silt and clay	Marine sand and silt, aeolian sand
SOIL Parent material	Marine sand and silt, aeolian sand	Paludal silt and clay	Marine sand and silt, aeolian sand
Description (Corangamite Soil Group)	Sodic red texture contrast soils (35)	Grey and brown cracking clay soils (37)	Sodic brown, yellow and grey texture contrast soils (36)
Soil type sites	LS15, LS8, LS23	LS3, LSWW9, LSWW5	LS2, LS13, LS24
Surface texture	Sandy clay loam	Medium clay	Sandy clay loam
Permeability	Moderate	Slow	Slow
Depth (m)	1.6	> 2	> 2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS Critical land features, processes, forms	Hardsetting soil surface (weakly structured) susceptible to sheet and rill erosion, and wind erosion where exposed. Dispersive and deep subsoils susceptible to gully erosion on steeper slopes. Topsoil may be susceptible to acidification.	Susceptible to inundation and waterlogging in lower areas, but can be variable due to micro relief (gilgai). Slightly susceptible to surface sheet erosion where soils are exposed. Surface soils friable and only slightly susceptible to wind erosion. Soils susceptible to compaction at critical moisture contents.	Susceptible to wind and sheet erosion where exposed. Low inherent soil fertility in well drained surface soil abruptly over structured subsoil. Susceptible to compaction where hardsetting with restricted drainage.

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