Land resource assessment in South Australia

South Australia has a relatively long history of soil survey and land resource assessment, with published soil surveys dating back to 1918. South Australia was home to several of the key identities associated with the early days of land and soil description and mapping in Australia. These included J.A.Prescott, C.G.Stephens, J.K.Taylor, and more recently Keith Northcote and Dick Blackburn. The first descriptions of soils in a continental context were made by J.A.Prescott (1931 & 1944). These were followed by three editions of A Manual of Australian Soils (Stephens 1953, 1956 & 1962), by which time the general nature and properties of the main soils of agricultural use in South Australia were understood. These early publications were superseded by A Handbook of Australian Soils (Stace et al 1968), and the Atlas of Australian Soils, Sheets 1-10 (Northcote et al 1960-68). These remain the benchmark publications for substantial areas of Australia where more detailed land descriptions have yet to be undertaken. The first stand-alone soil map of South Australia, based on the Atlas at a scale of 1:2,000,000 and comprising 111 mapping units, was compiled by Northcote (1968). At about the same time, Australia’s first objective soil classification system was being developed (Northcote 1960, 1965, 1971, 1979). This remained the official system until it was superseded by the Australian Soil Classification in 1996 (Isbell 1996, 2002).

Details of this work can be obtained from the publication A history of the CSIRO Division of Soils: 1927–1997, prepared by KE Leeand.

While this broad-scale work was being undertaken, there was considerable activity at regional and sub-regional levels, where more detailed information was required.

The Council for Scientific and Industrial Research (CSIR), its successor organization, the Commonwealth Scientific and Industrial Research Organization (CSIRO), and the South Australian Department of Agriculture were the key agencies involved during this period. Whilst some mapping and land description was conducted during the 1930s (e.g. in the Riverland and the Upper South East), the hey-day period of soil survey in South Australia was from the late 1940s through to the early 1970s.

The Department of Agriculture published significant regional land descriptions for the Northern and Yorke Agricultural Districts (French, Matheson & Clarke 1968), Eyre Peninsula (French 1958), and the northern Murray Mallee (Potter, Wetherby & Chittleborough 1973), whilst the CSIRO Division of Soils, whose Adelaide laboratories housed an active Pedology Section, undertook detailed survey work in the South East, Northern Districts, Kangaroo Island, Mt. Lofty Ranges, Barossa Valley and Lake Plains.

By the mid 1970s, the priorities of both the Department of Agriculture and CSIRO had changed, the main players were beginning to retire, and very few new pedologists were being recruited. Soil and land description in South Australia all but ceased.

Rapidly increasing awareness of environmental issues in the early 1980s caused a resurgence of interest in the importance of the sound use and management of soil and land, and the need for supporting data and information which was comprehensive, up-to-date and easy to use.

Commonwealth funding programs, notably the National Soil Conservation Program, came on-stream, and grants were available to community and producer groups, as well as State and Commonwealth agencies and universities. Collaborative projects involving land managers and agencies were encouraged. Thus began a landmark period which saw the rejuvenation of District Soil Conservation Boards, the birth of the Landcare Movement, and the spawning of a myriad of projects focussing on management of soil acidity, salinity, structure decline, water repellence, wind and water erosion, watercourse stability, tillage practices, rotations, vegetation management, pest control and so on.

There was renewed interest in farm planning (or property management planning as it soon became called) as a means of integrating the various issues now being tackled.

The dual need for credible information on the extent and distribution of a range of problems, and understanding of the nature and behaviour of SA’s wide range of agricultural soils, provided ample justification for the rekindling of a land resource assessment program.

With the rapidly developing need for better understanding of soils and their landscapes, and armed with hitherto unavailable computer technology, scientists from the Department of Agriculture embarked on a new era of land and soil assessment.

Whilst the existing surveys provided invaluable information, there were several significant limitations:

• The geographic coverage was still incomplete.
• The small scale of much of the mapping meant that detail was inadequate for use at the local level.
• Methodologies were inconsistent, so creation of continuous maps across regions was difficult.
• The information provided was not only inconsistent, but commonly difficult to interpret without specialist skills.

The aim of this new work was to generate a consistent and easily interpretable mapping coverage of the entire agricultural zone, with a clear focus on resource management. The project was undertaken by the Soil and Land Information Group, which began life in the Soils Branch of the Department of Agriculture. Commencing in 1990, the Group undertook a comprehensive field major program of soil and land description and mapping, and an associated series of field days aimed at sharing information about soils and soil management with landholders.

The project was a collaborative venture between the Department of Agriculture and its successors (PISA, PIRSA & DWLBC), and the National Soil Conservation Program, the National Landcare Program and the Natural Heritage Trust.

The assessment entailed a field program during which over 25,000 soil descriptions were made, mostly from samples collected with a hand soil auger. All land south of the Pastoral Leasehold Country, or Crown Lands were covered, and area of 15.75 million hectares. Features of the work were:

• Seamless mapping coverage of SA’s agricultural districts at a scale sufficiently detailed for planning at the district and catchment level.
• All data were entered in electronic format, including pioneering work on the use of geographic information system technology to store spatial (map unit) data. This enables an almost limitless range of maps and information to be generated by applying interpretation rules to the data, or combining it with other data.
• Mapping data were accompanied by information on specific soil or landscape attributes to enable non-specialists to better understand the nature of the data. Attributes included parameters such as salinity, susceptibility to waterlogging, rockiness, acidification potential, soil toxicities, erosion potential and so on.
• Models (or rules) for interpreting the data to predict suitability were developed for over 30 field crops, horticultural crops and pastures.
• Over 1000 soil pits were excavated on a wide range of soil types for the purpose of detailed analysis and ‘soils training’ (refer to next section). Two-page ‘soil data sheets’ including landscape and soil profile photographs, descriptions, laboratory data and interpretations were prepared for each site.
• All information was presented on DVD, and has recently become available on-line.
• A definitive text (The Soils of Southern South Australia – Hall et al) was published in 2009.

A significant and highly successful additional component of the mapping work was a training program in which the pits which had been dug in paddocks, vineyards and orchards for sampling soil, were also used as field day sites. About 150 ‘soil pit’ field days were held, at which land managers, extension and research people discussed various aspects of soil properties and soil management, using the pits and the data collected from them as a focus.

This aspect of the program formed an integral part of the property management planning initiatives being conducted from all Regional offices at this time.