15 Raw Soils
15.1 Concept of the Order
Raw Soils lack a distinct topsoil 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, debris-mantles underlain by permafrost, active screes, lagoons and tidal estuaries.
15.2 Correlation
Raw Soils correspond in part with very weakly developed recent soils of the New Zealand 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.
15.3 Occurrence
Raw Soils occur scattered throughout New Zealand, particularly in association with high mountains, braided rivers, beaches and tidal mudflats, steep scoria cones or very recently erupted or eroded andesitic tephras.
15.4 Accessory Properties of the Order
- No B horizons. Pedogenetic horizons are lacking apart from a rudimentary topsoil.
- Fresh or weakly weathered. Coarse rock fragments and sand particles are generally without coatings, although coarse 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 therefore 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.
15.5 Summary of Raw Soils Hierarchy
| Code | Group | Subgroup | Example Series |
|---|---|---|---|
| WW | Hydric | Sulfidic | - |
| Typic | - | ||
| WG | Gley | Sulfuric | - |
| Fluid-sulfidic | Takahiwai | ||
| Sulfidic | - | ||
| Fluid-saline | - | ||
| Saline | Takahiwai | ||
| Fluid | Paratai | ||
| Sandy | - | ||
| Typic | - | ||
| WH | Hydrothermal | - | Atiamuri |
| WC | Cryic | - | - |
| WX | Rocky | - | Alpine |
| WS | Sandy | Tephric | - |
| Typic | Riverton | ||
| WF | Fluvial | - | Selwyn |
| WT | Tephric | - | Tarawera |
| WO | Orthic | - | Alpine |
15.6 Key to Groups of Raw Soils
WW
Raw Soils with surface water present for a majority of the time (but not constantly).
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 Childs’ test 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.
WC
Other Raw Soils with a permafrost or evidence of cryoturbation within 1 m of the soil surface.
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% coarse 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 material without fluvial features.
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, but not always. They are commonly part of an active riverbed or other shore environment (coastal, lakes).
WWU
Hydric Raw Soils in which sulfidic soil material is present in some part within 90 cm of the mineral soil surface.
Sulfidic Hydric Raw Soils
WWT
Other soils.
Typic Hydric Raw Soils
WG - GLEY RAW SOILS
Gley Raw Soils occur in sites that are periodically or permanently flooded. Wetness is expressed in the soil by low-chroma colours with brownish or reddish mottles, by water saturation or is indicated by a chemical test for the presence of reduced iron (Childs’ test).
WGR
Gley Raw Soils in which sulfuric soil material is present in some part within 90 cm of the mineral soil surface.
Sulfuric Gley Raw Soils
WGFU
Other soils that have BOTH
- Moderately fluid or very fluid fluidity class at a depth of 30 cm or less, AND
- Sulfidic soil material is present in some part within 90 cm of the mineral soil surface.
Fluid-sulfidic Gley Raw Soils
WGU
Other soils in which sulfidic soil material is present in some part within 90 cm of the mineral soil surface.
Sulfidic 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
- Saline soil material.
Fluid-saline Gley Raw Soils
WGQ
Other soils that within 30 cm of the mineral soil surface have saline soil material.
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% coarse 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.
No subgroups have been defined.
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 erosion, transportation and deposition of sand, most commonly as dune sands.
WSK
Sandy Raw Soils containing tephric soil material from the soil surface to 30 cm depth or more.
Tephric Sandy Raw Soils
WST
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 deposits of pyroclastic origin, predominantly basaltic scoriae, with potentially minor additions of rhyolitic to andesitic 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, including debris-mantled slopes in alpine areas.
No subgroups have been defined.