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Changelog.qmd
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Changelog.qmd
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## Changes in the Fourth Edition
### Major
#### Diagnostics
- **ADD** clear definitions of the phrases 'in some part' and 'in the major part' to the top of the chapter.\
**Rationale** these were previously sitting in footnotes within the Allophanic and Brown chapters, making them hard to find.
- **ADD** [Anthropic Soil Material](Diagnostics.qmd#sec-diag-anthro) as a diagnostic for the Anthropic order.\
**Rationale:** Anthropic materials were not previously defined, causing confusion during the classification process.
- **ADD** [Eluvial horizon](Diagnostics.qmd#sec-diag-eluvh) as a diagnostic for Pallic and some Brown soils.\
**Rationale:** Concepts appearing in the key require a clear diagnostic definition within the classification, independant of the description manual, which was previously implicitly linked.
- **ADD** [Saline Soil Material](Diagnostics.qmd#sec-diag-salt) as a diagnostic.\
**Rationale:** Elevated soil salinity defines subgroups in the Gley, Semi-Arid, Recent and Raw orders but the concept has not been fully explained.
- **AMEND** [Calcareous horizon](Diagnostics.qmd#sec-diag-calch) for clarity and brevity, adding a clearer definition of primary vs secondary carbonates and including example horizon notation. Removed extraneous second paragraph.\
**Rationale:** Removal of the second paragraph is justified on the grounds that the content is better suited to the Methods and Rationale of the NZSC [@hewitt1993].
- **AMEND** [Densipan](Diagnostics.qmd#sec-diag-dens) to include expected horizon notation, and remove reference to specific types of field testing.\
**Rationale:** Strength and penetration resistance testing should be undertaken using current best practices, which do not need to be specified in this document.
- **AMEND** [Fragipan](Diagnostics.qmd#sec-diag-fpan) to include expected horizon notation, and remove reference to specific types of field testing. Additionally, clarify that bulk density is expected to be *greater than or equal to* 1.5 Mg/m^3^.
- **AMEND** the table in [Reactive Aluminium](Diagnostics.qmd#sec-diag-naf) test to match the new Soil Description Manual draft and demonstrate more realistic reaction colours.
#### Key
- **MOVE** [Anthropic soils](Key-to-Orders.qmd#sec-A) to the top of the key.\
**Rationale:** Removing Anthropic Soils from contention first can reduce confusion when applying the rest of the key, and keeps the overall classification structure relatively simple. The Australian Soil Classification with its Anthroposol order and the Japanese Soil Classification with its Developed/Reclaimed soils (造成土大群) make a similar choice. The World Reference base is effectively the same - it places its two equivalent orders (Anthrosols and Technosols, for agricultural and urban/industrial situations respectively) in second and third place after the Histosols. This reflects the rapidity with which organic soil materials can accumulate on the land surface. The Histosol definition itself allows for the presence of anthropic features like artefacts, so all human-modified profiles are effectively classified out early in the WRB key.\
By contrast, US Soil Taxonomy uses the Anthric and Plaggic Epipedon concepts to modify other orders. This has the advantage of keeping human-influenced soils conceptually close to their more natural neighbours, but adds a large number of subgroups to the classification, making it potentially more difficult to use. These subgroups will continue to proliferate as humans discover new and interesting ways to modify their environment. Other systems either ignore human-modified profiles or deliberately exclude them from consideration, neither of which practice is considered useful.
- **CHANGE** the criteria for [Recent Soils](Key-to-Orders.qmd#sec-R) to allow soils that do not fully meet the criteria for a [Distinct Topsoil](Diagnostics.qmd#sec-diag-dts) by only having a 'structural A' horizon.\
**Rationale:** This change helps to account for soils that have only a slight colour difference (e.g. visually perceptible darkening but still within the same Munsell chip, or only a Hue shift) in the A horizon due to tillage, low natural organic carbon content, or similar, but are still clearly too developed and in the wrong landscapes for the Raw order to make sense.\
The definition of [Distinct topsoil](Diagnostics.qmd#sec-diag-dts) itself is not proposed to be changed so that the definitions of other orders remain consistent.
- **ADD** an additional criteria that [Gley soils](Key-to-Orders.qmd#sec-G) do not contain a diagnostic amount of allophanic soil material (new criteria 1(e))\
**Rationale** soils that fail out on this new criteria belong more correctly in the LG [Allophanic Gley](Allophanics.qmd#sec-key-LG) group, and new criteria directs them there. Gleys that contain [tephric soil material](Diagnostics.qmd#sec-diag-teph) that doesn't meet the requirements for [allophanic soil materials](Diagnostics.qmd#sec-diag-alloph) (for example, gley soils forming in poorly drained alluvia from mixed sources but including some reworked ash), may still key out as GT [Tephric Gleys](Gleys.qmd#sec-key-GT).
- **ADD** a statement to the [Allophanic Soils](Key-to-Orders.qmd#sec-L) definition covering situations where [allophanic soil material](Diagnostics.qmd#sec-diag-alloph) is shallow over rock.\
**Rationale** Without this statement, shallow allophanic soils over rock are most likely to be pushed into the BL [Allophanic Brown](Browns.qmd#sec-key-BL) or RT [Recent Tephric](Recents.qmd#sec-key-RT) subgroups, neither of which may be the most appropriate destination.
- **ADD** an additional criteria to [Melanic soils](Key-to-Orders.qmd#sec-E) specifying the expected dominant soil parent materials.\
**Rationale** The Melanic order has been occasionally misinterpreted to apply to a wider variety of profiles with dark topsoils than was originally intended.
- **CHANGE** criteria 3b of Melanic soils to include some additional possibilities for soils below pH 5.9\
**Rationale** newly available data
#### Anthropic soils
- **ADD** group AO ([Māori Anthropic](Anthropics.qmd#sec-key-AO)), containing subgroups AOA ([Artefact Māori Anthropic](Anthropics.qmd#sec-key-AOA)), AOB ([Organic Māori Anthropic](Anthropics.qmd#sec-key-AOB)), and AOF ([Fill Māori Anthropic](Anthropics.qmd#sec-key-AOF)).\
**REMOVE** subgroup AFA (Artifact Fill Anthropic Soils).\
**Rationale** Māori soils have been previously recognised in the classification at a lower level and with less detail. Adding these groups and subgroups enables clear identification (particularly in mapping) and more effectively distinguishes them from other Anthropic soils.
- **ADD** subgroup ARW ([Wet Refuse Anthropic Soils](Anthropics.qmd#sec-key-ARW))\
**Rationale** These soils will break down in a different manner to other Refuse Anthropic Soils.
- **ADD** subgroups AMI ([Inverted-tephric Mixed Anthropic Soils](Anthropics.qmd#sec-key-AMI)), AMZ ([Inverted-impeded Mixed Anthropic Soils](Anthropics.qmd#sec-key-AMZ)) and AMT ([Typic Mixed Anthropic Soils](Anthropics.qmd#sec-key-AMT)).\
**Rationale** the previous lack of subgroups prevented the classification from being able to represent particular and very distinctive modern land modification practices.
#### Brown soils
- **ADD** subgroup BML ([Allophanic Mafic Brown Soils](Browns.qmd#sec-diag-BML))\
**Rationale** see comments on Melanic soils below
- **ADD** Subgroup BFF ([Placic Firm Brown Soils](Browns.qmd#sec-diag-BFF))\
**Rationale** new soil observations
- **ADD** Subgroup BFWA ([Acidic-weathered Firm Brown Soils](Browns.qmd#sec-diag-BFWA))\
**Rationale** new soil observations
- **ADD** Subgroup BFPA ([Acidic-pallic Firm Brown Soils](Browns.qmd#sec-diag-BFWA))\
**Rationale** new soil observations
- **ADD** Subgroup BOMP ([Mottled-pallic Orthic Brown Soils](Browns.qmd#sec-diag-BOMP))\
**Rationale** new soil observations
- **ADD** Subgroup BOWA ([Acidic Weathered Orthic Brown Soils](Browns.qmd#sec-diag-BOMP))\
**Rationale** new soil observations
- **REMOVE** requirement for no placic horizon in group BS ([Sandy Brown Soils](Browns.qmd#sec-key-BS))\
**Rationale** requirement was inconsistent with the existence of BSMP ([Mottled-placic Sandy Brown Soils](Browns.qmd#sec-key-BSMP)) within the group.
- **REMOVE** subgroup BLAM (Acidic-mafic Allophanic Brown)\
**Rationale:** With the additions made to the Mafic Melanic and Mafic Brown groups, this subgroup has become superfluous. Linking allophanic subgroups directly to mafic groups (EM, BM) will better account for the mechanisms behind the allophanic characteristics in these soils that are likely different to that of soils with allophanic characteristics from tephra and more felsic lithology.
- **AMEND** Mottled subgroups in the Brown Soils (BLM, BSMP, BSM, BMMG, BMM, BAMP, BAM, BFMA, BFMC, BFMW, BFMP, BFM, BOMA, BOM) to be defined by the presence of a mottled profile form *or perch-gley features*. This also applies to the new subgroup BOMP.\
**Rationale**: Perch-gley features can induce a profile form that is in part reduced, but not necessarily as strongly as is required for a gley soil. The reduction is often seasonal rather than year-round. These soils are usually considered imperfectly rather than poorly drained. For further discussion, see @hewitt2021, pp. 76-78.
- **MOVE** BAX ([Pan Acid Brown Soils](Browns.qmd#sec-key-BAX)) up one position in the key.\
**Rationale** this matches the order seen in the Pan Podzols.
#### Melanic soils
- **ADD** subgroups EML ([Allophanic Mafic Melanic](Melanics.qmd#sec-key-EML)), EMA ([Acidic Mafic Melanic](Melanics.qmd#sec-key-EMA)).\
**Rationale** Acidification, high P retention and presence of allophanic material in Melanic soils from mafic rock types (e.g., basalt) as observed under higher precipitation (\>800-1000 mm) does not necessarily lead to the loss of the typical characteristics of Melanic soils, such as the dominance of mafic parent material, dark-coloured Fe/Mg/Ti-rich minerals, smectitic clays, a well-developed pedality and higher organic carbon contents. Despite their lower soil pH and exchangeable bases, they are more closely related to soils in the existing EM group than they are to their former groups (BL, BM) in the Brown Soil order.
#### Raw soils
- **ADD** group WW ([Hydric Raw Soils](Raws.qmd#sec-key-WW))\
**Rationale** These soils are usually under shallow water (e.g. lower tidal areas, lake shores).
- **ADD** subgroups WST ([Tephric Sandy Raw Soils](Raws.qmd#sec-key-WST)) and WSS ([Typic Sandy Raw Soils](Raws.qmd#sec-key-WSS)).\
**Rationale** new soil observations
#### Recent soils
- **ADD** subgroups RXMA ([Mottled-acidic Rocky Recent Soils](Recents.qmd#sec-key-RXMA)) and RXM ([Mottled Rocky Recent Soils](Recents.qmd#sec-key-RXM)).\
**Rationale** new soil observations
### Minor
#### Correlations
- Discussions of correlations between the NZSC and other systems have been updated to reflect changes to both them and the NZSC.
#### Terminology
- **AMEND** the definition of [Cutanoxidic horizon](Diagnostics.qmd#sec-diag-cutoxh) to put all requirements in the numbered criteria list.
- **AMEND** the definition of [Densipan](Diagnostics.qmd#sec-diag-dens) to put all requirements in the numbered criteria list.
- **AMEND** the definition of [Duripan](Diagnostics.qmd#sec-diag-dpan) to include a horizon notation example.
- **AMEND** the definition of [Ironstone-pan](Diagnostics.qmd#sec-diag-ipan) to include a horizon notation example.
- **AMEND** the definition of [Tephric soil materials](Diagnostics.qmd#sec-diag-teph) to simpify the terminology list.
- **AMEND** the definition of [Truncated Anthropic](Anthropics.qmd#sec-AT) soils for clarity.
- **AMEND** the definition of [Mixed Anthropic](Anthropics.qmd#sec-AM) soils for clarity.
- **AMEND** the definition of [Refuse Anthropic](Anthropics.qmd#sec-key-AR) soils to specifically include plastics in 'manufactured organic material' and remove the requirement to attempt ignition of suspected methane.
- **AMEND** the definition of [Firm Brown Soils](Browns.qmd#sec-BF) to be more specific about the strength requirements.
- **AMEND** subgroup ZPOZ ([Peaty-silt-mantled Perch-gley Podzols](Podzols.qmd#sec-key-ZPOZ)); in requirement 1(b), 'pedality' was used where 'structure' should have been.
- **AMEND** group ZX ([Pan Podzols](Podzols.qmd#sec-ZX)) to be more specific about the strength requirements.
- **AMEND** group ZO ([Orthic Podzols](Diagnostics.qmd#sec-ZO)) to be more specific about excluded horizons.
- **AMEND** the definition of MOI ([Immature OrthicPumiceSoils](Pumices.qmd#sec-key-MOI)) to correct colour requirements.
- **RECODE** AFE (Earthy Fill Anthropic Soils) to AFT ([Typic Fill Anthropic Soils](Anthropics.qmd#sec-key-AFT)).
- **RECODE** BFAC ([Acidic-cemented Firm Brown Soils](Browns.qmd#sec-key-BFCA)) to BFCA.
- **RECODE** BFAL ([Acidic-allophanic Firm Brown Soils](Browns.qmd#sec-key-BFLA)) to BFLA.
- **RECODE** PXJM ([Argillic-mottled Fragic Pallic Soils](Pallics.qmd#sec-key-PXMJ)) to PXMJ.
- **RENAME** BAMP (Mottled-placic Acid Brown Soils) to BAMP ([Mottled-*impeded* Acid Brown Soils](Browns.qmd#sec-key-BAMP)).
- **REPLACE** use of the term 'calcium/magnesium ratio' with 'calcium/magnesium molar ratio'
- **REPLACE** various terms for in-profile stone \> 2 mm (e.g. clasts, gravel) with 'rock fragments'.
- **REPLACE** use of the term 'acid' with 'acidic' when used as a descriptor.
- **REPLACE** references to E horizons with cross-references to the new [eluvial horizon](Diagnostics.qmd#sec-diag-eluvh) diagnostic.
- **REPLACE** references to salinity cutoffs with cross-references to the new [Saline soil materials](Diagnostics.qmd#sec-diag-salt) diagnostic.
- **REMOVE** the phrase '(or some subhorizon of the B)' from the definition of the [Podzolic-B horizon](Diagnostics.qmd#sec-diag-podzb) (superfluous).
- **REMOVE** redundant reference to depth requirements in part 2 of the LOA ([Acidic Orthic Allophanic](Allophanics.qmd#sec-key-LOA)) soil definition.
#### Consistency
- **REMOVE** reference to 'stony brown' soil group in the Brown soils accessory properties list, point 8. This concept was retired between v2.0 and v3.0.
- **AMEND** all units to SI standards (e.g. CEC in cmol~c~/kg)
- Refer consistently to 'B or BC' horizons where appropriate.
#### References
- References have been updated where new editions or versions of certain documents have become available. New contextual references have been added in a number of places.
- A [Glossary](glossary.qmd) has been added.