Mt Lofty Block (Province 3)

This province comprises a well-defined zone of uplands extending from the southern extremities of the Flinders Ranges through the Fleurieu Peninsula in the south to the lower-lying Kangaroo Island. Generally the uplands are bounded on both the east and west by the steep escarpments, setting the province apart form the adjacent Provinces 2, 4 and 5.

Climatic conditions grade from temperate rainy in the south to drier warmer climates in the north and north-west. The escarpments along the western margin of the province produce orographic effects which result in high rainfall gradients with associated changes in vegetation and land use across the province. These are typified by a transect from Mt Lofty, with a mean annual rainfall of about 1100 mm, to the eastern scarp near Monarto, where mean annual rainfall is less than 400 mm. Temperatures vary from cool to cold in winter and from cool to hot in summer. Seasonal and diurnal ranges are low in the southern coastal areas and increase northwards and inland. Mean annual evaporation increases from 1600 mm on Kangaroo Island to 2400 mm in the north.

Landforms have marked northerly trending structural control. In the north, there are narrow strike ridges separated by wide intramontane plains. South of Gawler, ridges have smooth rounded slopes and broad, commonly flat-topped crests which, in the south, form undulating tablelands. These tablelands and flat-topped crests represent remnants of a former land surface that was uplifted during the Tertiary and is now in various stages of dissection. This surface, which has remnants of laterite capping, continues into Kangaroo Island, where it is well preserved. Several peaks such at Mt Lofty, Mt Torrens and Mt Gawler stand above the general summit level.

Open forests and low open forests once dominated the south of the province, with woodlands in the north and east. Mallee covers much of Kangaroo Island, but is now less prominent on the mainland where only small areas remain.

The mainland part of the province includes some of the most productive agricultural land in South Australia. It supports a wide range of activities from intensive horticulture to conservation, from recreation to extensive livestock grazing. This range of uses reflects both the variety of environmental conditions in the province and its adjacency to Adelaide.

Arable farming is confined mainly to the drier plains north of Gawler on moderately deep, well-drained red duplex soils (red-brown earths). These have good water-holding capacity, but intensive wheat-farrow rotation tends to deplete their fertility and damage their structure. Soil erosion is common and gullying is an increasing problem on these plains. Vineyards and fruitgrowing districts mainly have well-drained red duplex soils, but improved pastures for intensive livestock grazing are more commonly associated with yellow duplex soils which, under cultivation, are more prone to erosion and sever gullying than the red duplex soils.

In terms of broad land use categories, the Mt Lofty Block may be divided into three areas, the very intensively used lands adjacent to Adelaide; the intensive grazing lands of the Fleurieu Peninsula and the eastern plateau; and the arable farming and grazing areas of the remainder of the province.

The intensively used lands border the Adelaide urban areas and extend south through McLaren Vale, east beyond Crafers-Bridgewater and north-east to the Barossa Valley. This area has a particularly complex set of land resources which have been developed in a variety of ways through time so that is not only represents the most complex geographic pattern of land use in South Australia, but also the most dynamic area of land use conflict and land use change in the state. There are competing demands for land from long-established horticulturalists, new hobby farmers, conservationists, water conservation authorities, Adelaide recreationists, and livestock farmers ranging from horse stud owners to pig farmers. While many of these uses are compatible, others are not and the conflicts that ensue call for varying degrees of public as well as private decision making.

Further east and south mixed livestock grazing dominates the pattern of rural land use. Rainfall is in excess of 600 mm p.a. and from autumn to early summer provides adequate soil moisture for the growth of improved pastures which are the basis of the intensive livestock grazing activities. Local ground water supplies and farm dams are widely used to irrigate small areas of pastures and lucerne to supplement the non-irrigated pastures during summer. Both dairying and fat lamb breeding are supported on the best pastures. The area carries 40% of the State's dairy cattle. Both milk and lambs are destined for the Adelaide market.

In the remainder of the province land use patters are not closely tied to Adelaide and its markets. Grazing of sheep and some beef cattle is almost ubiquitous, occurring through more than 90% of the province. Livestock grazing also dominates the land use of Kangaroo Island and some higher ridges of the mid-north and north, where rotation cereal cultivation and livestock grazing are practised on the plains and the lower ridges. The two important commercial grains are wheat and barley, but oats is widely grown as a supplementary feedcrop for on-farm livestock.

Three regions are recognized in the province:

Kangaroo Island (Environmental Region 3.1)

Kangaroo Island, an undulating upland plain, is bounded by a cliffed coastline. Some dunes have developed along the southern coastline.

Peninsula Uplands (Environmental Region 3.2)

This extends from the Fleurieu Peninsula to the Barossa Valley and includes the moister parts of the Mt Lofty Ranges. It is predominantly an undulating to low hilly upland with steeper marginal ranges and hills.

Mid-North Wheatlands (Environmental Region 3.3)

This region, further to the north, is characterized by a series of wide undulating intramontane basins separated by low but distinct, northerly trending strike ridges. It is considerably drier than Regions 3.1 and 3.2. In the north the region adjoins Province 6, the Flinders Ranges along the approximate northern limit of wheat cultivation.