Soils of South Australia

South Australia’s soil diversity can be attributed to five dominant factors:

Parent material – in South Australia, the main parent materials are ancient basement rocks, a range of younger, often unconsolidated sediments laid down by wind and water, and older soils.
Climate – climatic conditions affect the rate of physical, chemical and biological soil forming processes. Past climates have led to extensive deposition of wind or waterborne sediments within which a distinctive range of soil types has formed. Climatic factors affecting soil formation are rainfall, wind, wetting and drying, temperature, streams and floodwaters, and lakes, lagoons and marine environments.
Topography – the position of a soil in the landscape influences different rates of erosion and deposition, drainage, and leaching. Soil depth is determined predominantly by position in the landscape.
Biological influences – soil organisms, plants, growing season, nature of organic matter and other factors that affect the proliferation of soil organisms. In turn, these influence mineral weathering, nutrient availability, and organic matter formation and decomposition in soils.
Time – the longer soil materials are acted upon by soil-forming processes, the more weathered, leached and infertile they become. Australia is geologically very stable and has not experienced mountain-building, glaciation, or widespread and frequent flooding for many millions of years so no unweathered, reactive materials from newly exposed rock have been widely deposited in more recent geological times.

South Australian soils are largely formed from ancient, highly weathered materials. Therefore, they are often inherently infertile and fragile and it is important they are carefully managed. The importance of appropriate soil management is emphasised by the fact that soil is effectively irreplaceable, given its very slow rate of natural formation.

Soils in the South Australian Agricultural Zone

The Soils of Southern South Australia (2009) publication provides comprehensive documentation of the State’s soil resources. It is designed to build knowledge and understanding of soils for those involved with managing, planning, research, education, ecology, industry development, or anyone interested in improving the management and condition of our precious soil and land resources.

This resource covers soil types (subgroups) present across the key agricultural regions including Eyre Peninsula, Kangaroo Island, Mount Lofty Ranges, Murraylands, South East and Yorke Peninsula. This resource is available for free download in two parts due to its size:

The Soils of Southern South Australia (2009) describes the 61 soil types (subgroups) found across the agricultural zone. These are grouped into 15 Major Soil Groups, based on their most significant profile features (i.e. physicochemical attributes). Their distribution across South Australia is shown in the map below and their key properties are summarised in the following factsheet:

The Soils of Southern South Australia - Summary of Major Soil Groups

Map showing the 15 major soil groups and their distribution in southern South Australia. — The distribution of major soil groups across southern South Australia (SA Agricultural Zone). Source: DEW

This book also outlines 10 ‘major soil features’ which are of critical importance for land use and management in South Australia:

Soil Constituents (mineral fraction, porosity, organic matter, water content etc.)
Soil Fertility
Toxic elements
Soil Structure
Drainage
Salinity
Soil Carbonates
Soil Depth
Waterholding Capacity
Erosion

These soil features (attributes) constrain land use potential and need to be effectively managed to support/protect soil productivity. These are summarised in the following factsheet:

The Soils of Southern South Australia - Summary of Major Soil Features

Additionally, the Soils of Southern South Australia (2009) also provides a comprehensive framework for describing, analysing and interpreting soil physical and chemical properties that influence agricultural productivity, providing the scientific foundation for more sustainable land management. This interpretation framework is summarised in the following factsheet: