Level Up

Appendix 1

Use of codes and confidence levels in recording classification of soil profiles

Use of codes

Examples of a coded classification of a soil profile are presented below. The codes are listed in the following order: Confidence level, Order, Suborder, Great Group, Subgroup, Family criteria. Note that the general written form of the classification is largely in reverse order with the following syntax: Subgroup, Great Group, Suborder Order; Family criteria, (Confidence level).

This ordering is not prescriptive and the manner in which the classification is recorded on field data sheets is an operational matter. However, the national standard soil profile database design, developed by the Australian Collaborative Land Evaluation Program (ACLEP), specifies that the coding system outlined in this classification is to be used for data exchange.

Example 1

1 CH AA AH AT A F L O T
This would decode as Bleached, Eutrophic, Red Chromosol; thin, slightly gravelly, loamy, clayey, very shallow, (Confidence level 1).

Example 2

If a level within the classification hierarchy is indeterminable from the available information this may be coded as [YY] but only if classes at the lower level are applicable:
4 KA AA YY BU
Ferric, ?, Red Kandosol; (Confidence level 4).
where YY is defined as: Class undetermined.

Example 3

If there is no available class this should be coded as [ZZ]:
1 RU ER ZZ AR
Basic, n/a, Stratic Rudosol; (Confidence level 1)
where ZZ is defined as: No available class

Example 4

If only a subset of the family criteria has been recorded then this should be coded as follows:
1 TE IN EA AI A - K K -
Acidic, Petroferric, Red Tenosol; thin, -, sandy / sandy, -, (Confidence level 1).
where - is defined as: Not recorded

In this example it is important to note that family criteria with a code of ‘K’ is valid for ‘A1 horizon texture’ and ‘B horizon maximum texture’. Recording of all the family criteria is essential. In order to avoid any future confusion or ambiguity, it is essential to record the family criteria in the same order as they are presented in the publication.

Confidence level of classification

In a number of instances it will not be possible to fully classify the soil because of a lack of laboratory data. It is desirable to indicate the level of confidence (1-4) when any attempt at classification is made.
  1. All necessary analytical and/or morphological data are available for the profile being classified.
  2. Necessary analytical data for the profile are incomplete but are sufficient to classify the soil with a reasonable degree of confidence, e.g. free iron oxide data may be lacking but it is known that the soil is formed from basalt. Such a soil invariably has >5% free iron oxide and would be considered a Ferrosol. Soils with all necessary analytical and/or morphological data but only to a limited profile depth may also fit this confidence level.
  3. No necessary analytical data are available for the profile but confidence is fair, based on a knowledge of similar soils in similar environments, e.g. presence of columnar structure is normally a reliable indicator of sodic soils (Sodosols).
  4. No necessary analytical data are available for the profile and the classifier has little knowledge or experience with this kind of soil, hence the classification is provisional.