Soil/Landform Unit 160

The undulating coastal plains of the south-west coast that are used for dairy farming

Area:

7292 ha

0.55% of CMA region

Rolling dissected hills of the southern Heytesbury region are formed from Miocene marine clay, marl and limestone, and Recent clay sand and gravel. This stretch of rolling hills extends from Newfield to Princetown. Slumping of the landscape has led to occasional steep scarps, but most slopes are long, gentle and straight, separated by broad drainage lines. Significantly this unit varies from soil-landform unit

165

due to the occurrence of residual near level crests with cappings of Neogene sediments within this unit. Soils on these Miocene sediments are typically brown, grey and black texture contrast soils, with heavier textured cracking clays lower in the landscape. Free lime is often present at depth in the soil profile. Soils on these sediments are significantly more fertile than the soils formed on the Neogene sediments of the crests. These soils tend to be weakly structured. Profile drainage is good on all but those areas with hardpans. Nearly all native vegetation has been cleared as part of the soldier settlement. Dairy farming is the main land use. Subsoils are dispersible and gully erosion has occurred along some drainage lines. Landslip and slumping is a major engineering issue that escalates when soils are waterlogged. Drainage lines and lower slopes remain waterlogged for most of the year and are prone to soil

compaction

(pugging) by stock.

The 12 apostles and undulating coastal plains of the south-west coast
	Limestone plateau north of Princetown

Component	1	2	3	4	5
Proportion of soil-landform unit	17%	5%	45%	25%	8%
CLIMATE Rainfall (mm)	Annual: 900-1000, lowest January (40), highest August (120)
Temperature (^oC)	Annual: 14, lowest July (9), highest February (18)
Seasonal growth limitations	Temperature: less than 10^oC (av.) June-August Precipitation: less than potential evapotranspiration November-March
GEOLOGY Age and lithology	Miocene marine marl and minor Recent clay, sand and gravel
Geomorphology	6.2.2 Dissected plains, rises and low hilss of the Sedimentary Western Plains
LANDUSE	Cleared areas: Dairy cattle, grazing beef cattle; sheet Minor uncleared areas: Nature conservation
TOPOGRAPHY Landscape	Rolling dissected hills with remnant plain cappings
Elevation range (m)	3-174
Local relief (m)	30-60
Drainage pattern	Parallel
Drainage density (km/km²)	3.3
Landform	Ridges	Fault scarps	Hillslopes		Drainage lines
Landform element	Crests and upper slopes	-	Mid slope, crest	Lower slope	-
Slope and range (%)	5 (2-9)	29 (57-37)	11 (4-21)	4 (1-7)	0 (0-1)
Slope shape	Convex	Concave	Convex	Concave	Linear
NATIVE VEGETATION Structure	Low woodland (variable)	Open forest	Woodland	Woodland	Closed scrub
Dominant species	E. nitida, E. baxteri	E. obliqua, E. baxteri, E. ovata, Acacia melanoxylon	E. ovata, E. radiata	E. obliqua, E. ovata	Melaleuca squarrosa, Leptospermum lanigerum
SOIL Parent material	Sand	Clay and silt; some lateritic remnants	Colluvial/alluvial marl and sand	Colluvial/alluvial marl and sand	Plant remnants, alluvial sand and clay
Description (Corangamite Soil Group)	Grey sand soils with hardpans (29)	Grey sand soils with hardpans (29) and mottled brown, grey, yellow and red gradational soils (17)	Mottled brown, yellow and grey texture contrast soils, coarse to fine structure (20)	Mottled brown, yellow and grey texture contrast soils, coast to fine structure (20)	Grey gradational soils (22)
Soil type sites	OTR608, OTR742	OTR608, OTR785	SW53, SW77, SW82	SW53, SW77, SW82	OTR733, CLRA10
Surface texture	Loamy sand	Loamy sand to sandy loam	Sandy loam to clay	Sandy loam to clay	Silty loam
Permeability	Very low	Moderate	Very low	Very low	Low
Depth (m)	>2	>2	>2	>2	>2
LAND CHARACTERISTICS, POTENTIAL AND LIMITATIONS	Weakly structured sands on hardpans are prone to sheet erosion and seasonal waterlogging. Permeable surface sands of high acidity and low inherent fertility are prone to nutrient decline.	Low inherent fertility, phosphorus fixation and permeable surfaces lead to nutrient decline. Steep slopes with weakly structured suface soils of low water holding capacity are prone to sheet erosion.	All slopes are subject to periodic saturation are prone to severe waterlogging and pugging by cattle. Landslips and slumping of road batters are a major hazard. Soils respond well to subsurface drainage including mole drainage.	Soils are prone to severe waterlogging and pugging by cattle. Saline discharge occurs at toe slopes of landslides and in some drainage lines. Soils respond well to subsurface drainage including mole drainage.	Dispersible subsoils of low permeability receiving runoff from surrounding hills are prone to gully erosion, waterlogging and soil compaction.

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