Raw Soils
Concept of the Order
Raw Soils lack distinct topsoil development or are fluid at a shallow depth. They occur in environments where the development of topsoils is prevented by rockiness, by active erosion, or deposition. They include beach sands, alpine rock areas and active screes, lagoons and tidal estuaries.
Correlation
Raw Soils correspond in part with very weakly developed recent soils of the NZ Genetic Soil Classification, and in part with materials that were often not considered to be soil. They are either Entisols or are unclassified in Soil Taxonomy.
Occurrence
Raw Soils occur scattered throughout New Zealand, particularly in association with high mountains, braided rivers, beaches and tidal mudflats.
Accessory Properties of the Order
- No B horizons. Pedogenetic horizons are lacking apart from a rudimentary topsoil.
- Fresh or weakly weathered. Rock fragments and sand particles are generally without coatings, although rock fragments in some screes may have weathering rinds.
- Inherited mineralogy. The soil mineralogy is very similar to that of the parent material and a range of mineralogy classes is possible.
- In soils with a fluid subsurface layer, a continuously high water-table is present. The deposition of fresh sediment may occur.
- Non-fluid soils occur in environments with active erosion or deposition.
- Low fertility. Nitrogen in particular, is deficient.
- Erosive. Most materials are unaggregated and likely to be highly erosive.
- Sparse vegetation. Vegetation is either absent, sparse or patchy, often consisting of ephemeral herbaceous plants, mosses or lichens. Mangroves occur mainly on Raw Soils.
Summary of Raw Soils Hierarchy
| Code | Group | Subgroup | Example Series |
|---|---|---|---|
| WW | Hydric | - | - |
| WG | Gley | Fluid-sulphidic | pt. Takahiwai |
| Sulphidic | | ||
| Fluid-saline | | ||
| Saline | pt. Takahiwai | ||
| Fluid | pt. Paratai | ||
| Sandy | | ||
| Typic | | ||
| WH | Hydrothermal | Active | - |
| WX | Rocky | - | pt. Alpine |
| WS | Sandy | - | pt. Riverton |
| WF | Fluvial | - | pt. Selwyn |
| WT | Tephric | - | pt. Ngaruhoe |
| WO | Orthic | - | pt. Alpine |
Key to Groups of Raw Soils
WW
Raw Soils with surface water present for a majority of the time.
WG
Other Raw Soils that at 30 cm or less from the mineral soil surface have either
- the upper boundary of a reductimorphic horizon, or
- sufficient active ferrous iron to give a positive reaction to α,α’-dipyridyl at some time in the year, or
- are saturated for 30 or more consecutive days in most years.
WH
Other Raw Soils that have mean annual soil temperature at 30 cm depth of at least 2.5°C more than the mean annual air temperature.
WX
Other Raw Soils with a lithic or paralithic contact within 30 cm of the soil surface.
WS
Other Raw Soils that have sand or loamy sand texture and that have less than 35% rock fragments (by volume) in all horizons, from the soil surface to 60 cm depth or more.
WF
Other Raw Soils that have fluvial features and are not buried by more than 30 cm of nonfluvial soil material.
WT
Other Raw Soils in tephric soil material from the soil surface to 30 cm depth or more.
WO
Other Raw Soils.
Key to Subgroups of Raw Soils
WW - HYDRIC RAW SOILS
Hydric Raw Soils have surface water present for a majority of the time. They are commonly parts of active riverbeds or other shore environments (coastal, lakes).
No subgroups have been defined.
WG - GLEY RAW SOILS
Gley Raw Soils occur in sites that are periodically or permanently flooded. Wetness is expressed in the soil by grey colours with brownish or reddish mottles, by water saturation or is indicated by a chemical test for the presence of reduced iron.
WGFU
Soils that have both
- moderately fluid or very fluid fluidity class at a depth of 30 cm or less, and
- pH more than 4.0 and pH in boiling hydrogen peroxide less than 3.0, in some horizon at less than 90 cm from the mineral soil surface.
Fluid-sulphidic Gley Raw Soils
WGU
Other soils that have pH more than 4.0 and pH in boiling hydrogen peroxide less than 3.0, in some horizon at less than 90 cm from the mineral soil surface.
Sulphidic Gley Raw Soils
WGFQ
Other soils that within 30 cm of the mineral soil surface have both
- moderately fluid or very fluid fluidity class, and
- electrical conductivity of 0.8 mS/cm.
Fluid-saline Gley Raw Soils
WGQ
Other soils that within 30 cm of the mineral soil surface have electrical conductivity of 0.8 mS/cm or more.
Saline Gley Raw Soils
WGF
Other soils that within 30 cm of the mineral soil surface have moderately fluid or very fluid fluidity class.
Fluid Gley Raw Soils
WGS
Other soils that have sand or loamy sand texture and that have less than 35% rock fragments (by volume) in all horizons, from the soil surface to 60 cm depth or more.
Sandy Gley Raw Soils
WGT
Other soils.
Typic Gley Raw Soils
WH - HYDROTHERMAL RAW SOILS
Hydrothermal Raw Soils occur in active hydrothermal areas affected by hot liquids or steam.
WHA
(only one subgroup recognised).
Active Hydrothermal Raw Soils
WX - ROCKY RAW SOILS
Rocky Raw Soils occur on rock outcrops subject to erosion. The soil volume available to roots is severely restricted.
No subgroups have been defined.
WS - SANDY RAW SOILS
Sandy Raw Soils occur in areas of active sand erosion, transportation and deposition, most commonly as dune sands.
WST
Soils in tephric soil material from the soil surface to 30 cm depth or more.
Tephric Sandy Raw Soils
WSS
Other soils.
Typic Sandy Raw Soils
WF - FLUVIAL RAW SOILS
Fluvial Raw Soils occur in sediments deposited by flowing water. They occur on land surfaces on which there is a high risk of flooding.
No subgroups have been defined.
WT - TEPHRIC RAW SOILS
Tephric Raw Soils occur in unconsolidated sediments of volcanic origin including ash, cinders, lapilli, pumice and other pyroclastic material.
No subgroups have been defined.
WO - ORTHIC RAW SOILS
Orthic Raw Soils occur in land that is being eroded, on rock outcrops or land that has received sediment emplaced primarily by slope processes.
No subgroups have been defined.