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Appendix 7

Summary of the changes in the third edition

The main changes in the third edition accommodate existing knowledge and understanding of the significance, nature, distribution and refined testing for soils comprising deep sands. This involved the introduction of a new Soil Order, the Arenosols. The introduction of the Arenosols Order also led to a review and changes to Calcarosols, Tenosols and Rudosols.

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.

The important points to note for the orders affected, plus other improvements throughout the text, are summarised below:

Arenosols

  1. Deep sands (sands at least 1.0 m deep) formerly classified as Calcarosols, Tenosols and Rudosols now classify as Arenosols.
  2. Soils with >10% coarse fragments and/or hard segregations (by visual abundance and weighted average in the top 1.0 m) are excluded from the Arenosols Soil Order.
  3. Horizon development may be absent in some Arenosols previously described as Rudosols.
  4. Some Podosols could be initially classified as Grey or Bleached Arenosols if investigation of the profile stops before reaching a diagnostic horizon (Bs, Bhs or Bh).
  5. Deep sands with pedogenic carbonates previously classified as Shelly, Calcic or Hypocalcic Calcarosols will now classify as Carbonatic or Calsilic Arenosols.
  6. The Tenosol Great Groups formed the basis of the Arenosol Great Groups but other forms are included. Additional Great Groups include Gritty (mainly granitic sands), Kandic (sandy loam B horizon with ~10-15% clay - soils transitioning to a Kandosol), Palic (clay <5%), Tenic (clay ~5-10%), Gravic (heavy mineral sands) and Subhalic, Hypocalcic, Lithocalcic, Supracalcic, Hypercalcic and Calcic.
  7. Text in the How to Classify section provides tips on how to determine if a deep, more clayey horizon (often >1.0 m deep) is a B or D horizon. This helps in determining if the soil is an Arenosol or some other soil Order.

Calcarosols

  1. In the key to Soil Orders, the criteria for Calcarosols are changed to exclude deep sands.
  2. The Shelly Suborder has been removed and replaced by the Carbonatic Suborder.

Ferrosols

  1. A Leptic Great Group is added.

Hydrosols

  1. An Arenosolic Great Group is added to the Extratidal, Salic, Redoxic and Oxyaquic Suborders.

Kandosols

  1. The requirement in the definition of "Do not have a tenic B horizon" is removed and the requirement for the B2 horizons to be "well-developed" removed from the key.
  2. Andic and Leptic Great Groups are added.

Organosols

  1. The Order definition now includes mineral horizons and unconsolidated mineral materials (no thicker than the organic materials above) to allow many shallow soils dominated by organic materials to be classified as Organosols.
  2. Melanic horizon material is added to the Order definition.
  3. The Suborder definitions reflecting peat dominance are modified to improve usefulness and clarity.
  4. New data from Tasmania has necessitated the expansion of the Family criteria to six. The new criteria are: Nature of altered organic materials; Cumulative thickness of uppermost organic materials; Gravel of the surface horizon; Dominant texture of the uppermost organic materials; Dominant texture of the B, C or D horizons directly underlying the deepest organic materials and Soil depth.
  5. The criteria Cumulative thickness of organic materials and Nature of uppermost organic materials have been removed.
  6. The new Nature of altered organic materials Family criterion caters for soils modified by fire or drying. It includes the Fusic and Ashy diagnostic features that were formerly included at the Subgroup level, and the Granular diagnostic feature that was formerly included in the Nature of uppermost organic materials criterion.

Rudosols

  1. The Shelly definition is amended to provide clarity.
  2. Coquinic, Petrocalcic, Lithic and Regolithic Great Groups are included for Shelly Rudosols.
  3. The Arenic definition is amended to be consistent with Arenosols.
  4. The six Great Groups currently available for Leptic Rudosols are now available for Arenic Rudosols as well. Previously no Great Groups had been proposed for the Arenic Suborder.
  5. The set of families available has been expanded from two to six and is now consistent with other Orders.
  6. The Silpanic and Gritty Great Groups have been added to the Arenic and Leptic Suborders.

Tenosols

  1. The term Orthic is now redundant and removed from Tenosol Suborders.
  2. The concept of a tenic B horizon is removed.
  3. The definition of the Calcenic Suborder is amended i.e. from 'pedogenic carbonate' to 'fine-earth carbonate'.
  4. For consistency, the Arenic Great Group is keyed out before Inceptic, Lithic, etc.
  5. The definition of Arenic is amended to be compatible with Arenosols.
  6. Shelly Tenosols are removed and classify as either Arenosols or Rudosols.
  7. Various Gritty Great Groups are added.
  8. The 13 Subgroups previously available for Bleached-Orthic are now available for the coloured Suborders as well, but four Subgroups (Subpeaty, Subhumose, Submelacic and Submelanic) are no longer available.
  9. The Silpanic Great Group has been added to the Chernic-Leptic and Leptic Suborders.

Other changes

Other important, but less substantial, changes are incorporated into the third edition. These mainly aim to improve clarity and consistency, and also align with definitions in the Australian Soil and Land Survey Field Handbook (NCST 2009), referred to in this publication as the Field Handbook (the Field Handbook is also colloquially known as the Yellow book due to the colour of its cover).

  1. An amended Figure 1 to match the order in the Key to Soil Orders.
  2. Each Soil Order is accompanied by a map of its distribution.
  3. Where appropriate, 'B2' horizon is replaced by 'B2t'.
  4. In the key, the term 'structure' is replaced by 'grade of pedality'.
  5. 'Soft, finely divided carbonate' is replaced with 'fine-earth carbonate'.
  6. To improve clarification of terminology, the glossary is expanded with additional terms and definitions, including some from the Field Handbook.
  7. Some definitions in the glossary are amended to align with the Field Handbook. In some cases the definitions are changed in both publications - these changes will be reflected in the next edition of the Field Handbook.
  8. Colour classes are explained more fully including, for digital versions, a table in colour.
  9. Confidence levels are rewritten for greater clarity.
  10. Several new references are included and some older ones updated.
  11. A water repellence Family criterion is added for surface soils of susceptible Orders.
  12. Consistent use of metric units throughout the publication - millimetres for sizes/depths ≤0.1 m (e.g. 50 mm) and metres for sizes/depths ≥0.1 m (e.g. 0.5 m).
  13. 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.