Preface to the Third Edition
With the first edition of the Australian Soil Classification, the availability of classified soil profiles was skewed towards Queensland (46.6%) due to the limited accessibility of good quality data. That situation has dramatically changed, with a greater proportion of quality sites now available from most other states or territories. The period 1996 to 2018 saw a tenfold increase (from 14,054 to 143,112) in classified profiles (Table 1), and the number of sites available with an Australian Soil Classification is increasing each year. The available dataset is now far more representative of Australian soils and their properties, providing good evidence for the significant changes in this new edition of the Australian Soil Classification.
Table 1 Number (percentage) of sites classified to at least Soil Order in 1996 and 2018
| State/Territory | Area % | 19961 | 20181 |
|---|---|---|---|
| ACT | <1 | 42 (0.3%) | 731 (0.5%) |
| NSW | 10.4 | 2250 (16%) | 21325 (14.9%) |
| VIC | 3 | 1142 (8.1%) | 7070 (4.9%)3 |
| QLD | 22.5 | 6550 (46.6%) | 45122 (31.5%) |
| SA | 12.7 | 1524 (10.9%) | 19645 (13.7%) |
| WA | 33.0 | 1327 (9.4%) | 14721 (10.3%) |
| TAS | 0.9 | 488 (3.5%) | 4890 (3.4%) |
| NT | 17.5 | 734 (5.2%) | 29607 (20.7%) |
| AUSTRALIA | 100 | 14057 (100%) | 143112 (100%) |
Sources:
1 Australian Soil Classification, first edition (Ray Isbell 1996)
2 National soil site data collation for the Australian Soil Landscape Grid 2018 (Peter Wilson and Ross Searle, CSIRO)
3 Victorian soils database (Mark Imhof, Agriculture Victoria, 2019)
The revised, second and third editions of the Australian Soil Classification have been the result of this ongoing data collection and improved understanding of gaps in soil knowledge. The Working Group on Land Resource Assessment prepared the revised edition, published in 2002. To manage the ongoing updating of the classification, the National Committee on Soil and Terrain (NCST) established the Australian Soil Classification Working Group in 2013 to assess proposals for change and make recommendations to the NCST. Following recommendations by the Working Group, in 2016 the NCST released a second edition to accommodate new knowledge and understanding of soils containing sulfidic materials. Included in these changes was the introduction of subtidal and subaqueous soils. Soils with abundant ironstone gravels were also accommodated by a Sesqui-Nodular Suborder in Tenosols.
The modifications incorporated into this third edition are the second approved recommendations from the Working Group. The most prominent modifications relate to definitions and expanding of the key to accommodate an Arenosol Soil Order for deep sands, as proposed by Noel Schoknecht (WA). Deep sands were previously classified as Tenosols, Rudosols or Calcarosols. These Soil Orders have extreme morphological diversity and have been subject to extensive investigation, particularly in South Australia, south-west Western Australia and the Northern Territory.
This major change to the classification was subjected to widespread consultation within the Australian soil science community over two years. Feedback from this consultation was strongly positive but not universally so. However, it led to a number of constructive changes to the original proposal.
Changes in the third edition
The main change in the third edition accommodates new knowledge and understanding of the significance, nature, distribution and refined testing for soils comprising deep sands, leading to the inclusion of a new Order, the Arenosols. The introduction of the Arenosol Order led to a review and changes to Calcarosols, Tenosols and Rudosols, and an opportunity to update the Organosol key based upon new and recently acquired soil data.
Another significant change is the removal of the weakly developed tenic B horizon concept from the classification. Experience shows the concept is of little assistance in soil classification. It is not explicitly defined and therefore cannot be consistently determined, limiting its value as a classification criterion.
Small-scale indicative soil distribution maps have been added for each Soil Order. These maps are updates of the distribution maps found in the Concepts and Rationale of the Australian Soil Classification (Isbell et al. 1997). They are a re-interpretation of Ray Isbell's original assessment of the most likely Soil Order in each map unit of the 1:2 000 000 scale Atlas of Australian Soils (Northcote et al. 1960-1968), with allowance for subdominant occurrences in a map unit where the Soil Order is common but not dominant.
Guidance is now provided for soil classification at Great Group and Subgroup level where the diagnostic feature for a class begins more than 1.5 m below the soil surface.
The important points to note for the orders affected, plus other improvements throughout the text, are summarised in Appendix 7.