| Code | Name | Description |
|---|---|---|
| E | Mapping exploration | Reconnaissance descriptions, or profiles described in the early stages of building knowledge to underpin, for example, a soil map. They may have biased or opportunistic sample locations (e.g. chosen during fieldwork) and moderate location precision. |
| V | Mapping validation | Profiles described when there is already a substantial knowledge base from previous work, with the purpose of gap‑filling or refining. They may be low‑detail, as their main role is to confirm or disprove predictions. |
| R | Research | Profiles described to support a scientific investigation, which may or may not be related to soil mapping. These are often predetermined by a model and located with high precision. |
| M | Monitoring | Profiles described at locations that will be visited more than once. This code implies ongoing measurements, with an expectation of minimal major disturbance between visits. |
| T | Reference | Calibration profiles that provide a definitive description and analysis of a soil type, serving as benchmarks for consistent classification. They typically have high morphological detail and extensive analytical data, representing ‘ideal’ profiles for particular soil classes. |
| D | Development | Profiles described to inform proposed or planned changes to the land, such as altering land use or undertaking construction. They are often part of resource consent planning. The soil may be removed or sealed after observation, limiting data reuse potential. |
9 Profile description
9.1 Defining the site
Soil profiles are described at sites. The site concept is necessarily somewhat flexible to account for a wide range of observation purposes and sampling methods. Generally speaking it is considered to include the immediate surroundings of a profile description, up to a maximum radius of ~10 m, so it will generally sit within a single landform. Where a site is close to a landform edge and the processes operating on the neighbouring landform are not judged to affect the profile being described, those neighbouring landforms should be ignored.
Multiple profile descriptions made across larger sampling plots or along transects that cross multiple landforms (or even landscapes) should usually be treated as a series of related sites rather than a single site.
The soil profile description starts with an observation of the local land surface and works downwards through the soil profile towards the underlying parent material. The chief tasks are assessing the surface, delineating pedologic horizons (and any additional geogenic layers, if present), and describing their morphological character.
Before beginning a soil profile description it is essential to record some additional reference data.
9.2 Reference data
Reference data are metadata that clearly identify a soil profile description. These data enable the description to be linked with other profiles, samples, analytical results, and photographs. Reference data include:
- an identifier
- who completed the description
- where the description was located
- when the description was done
- why the description was needed
- how the location was chosen
- what equipment was used
- depth of observation.
These data are discussed in turn below.
9.2.1 Identifier
Assign each profile description an identifier that is at least unique at a whole-of-project level, and preferably at a whole-of-organisation level. There are many ways to build identifier systems (see Note 9.1), but a good system usually has a predictable structure, is open-ended, and is easy to remember. Incorporating location data into the identifier can help avoid confusion between multiple projects within an organisation; for example, a region code followed by a sequential number: WLG_001.
This kind of identifier is ‘semi-unique’ in that there is still some potential for confusion if the data are combined with data sets from other sources; for example, a vegetation survey group working independently in the same region may have decided to use the same naming protocol for their descriptions.
9.2.2 Authors
Each soil profile description must have a single author responsible for it. Record their name. Additional participants should also be recorded (soil description is often a group activity). Where sample chain of custody needs to be tracked, recording the name of the sampler may also be necessary.
9.2.3 Location
Record location coordinates as eastings and northings in New Zealand Transverse Mercator (e.g. 1586090E, 5405720N). Location coordinates are the minimum requirement for location (see Section 9.3.1 for full requirements).
9.2.4 Date of observation
Record the date of observation using the ISO 8601 standard, YYYY-MM-DD (International Organization for Standardization 2019); for example, 2025-01-01. Recording the time is not essential, but is recommended because it can be useful for correlating soil profile descriptions with photographs or other data recorded using digital means (e.g. GPS tracks, environmental sensor data). If recording time, use the 24-hour format; for example, 14:35 for 2:35 pm.
9.2.5 Purpose
The original task for which a profile description was completed can affect what data were recorded and is relevant to data reuse decisions. Record the reason for observing the profile using the schema in Table 9.1. This parameter does not need to be recorded in the field.
9.2.6 Location selection method
Spatial sampling strategies vary in their statistical properties. Soil data are stored for long periods and are often reused for multiple projects; specific reuses may not be appropriate or may require that certain permissions be obtained.
Record the spatial sampling strategy using the schema in Table 9.2. This parameter does not usually need to be recorded in the field.
| Code | Name | Description |
|---|---|---|
| A | Arbitrary | Locations chosen while in the field in response to direct observation of on-ground conditions. These are often practical and time-efficient, but are also likely to over-sample the more easily accessible and/or interesting parts of the landscape, to the detriment of overall representativeness. |
| D | Data-driven | Locations chosen before a field visit using a loose set of rules or principles (e.g. 'Visit the major landforms on this farm but stay close to tracks'). They may be subject to minor changes once on-site. |
| M | Model-based | Locations chosen before a field visit using a deterministic and replicable set of rules, including rules for relocating sites where on-ground conditions make this necessary. |
| R | Random | Locations chosen by a randomised method, including stratified-random sampling. |
| T | Transect | Locations chosen to form a line over the land surface, with or without regular spacing. |
| G | Grid | Locations chosen to form a regular or semi-regular lattice over the land surface. |
A (arbitrary), D (data-driven), and M (model-based) sampling all represent attempts to use secondary environmental data sources to increase the efficiency of fieldwork, with the goal of minimising total workload while maximising the representativeness and quality of information gathered at each location. The success of these strategies depends on whether relevant and accurate model inputs are available.
R (random), T (regular) transect and G (regular) grid sampling effectively ignore environmental parameters, although stratified random sampling might partially incorporate such information. These strategies are useful when the spatial distribution of a parameter of interest is unknown or poorly understood, but can lead to profile descriptions being made in inefficient or unsafe locations.
Some of these methods can be used in a sequence that progressively narrows down the choice of location (e.g. data-driven transect locations across a whole study area, then randomised final locations along each transect). In such cases, the ‘last choice’ should be recorded on the profile description – in this example, R. The details of the full sampling strategy should be discussed in project metadata.
9.2.7 Profile exposure method
The method by which the soil was exposed for observation affects which parameters can be recorded, or at least recorded reliably. Record the profile exposure method using one of the options in Table 9.3.
| Code | Name | Description |
|---|---|---|
| P1 | Standard pit | Pit or trench >1 m wide, exposing the complete profile to regolith or bedrock |
| P2 | Minimal pit | Pit up to 0.5 m wide and generally no deeper than 1 m |
| E | Exposure | Road cutting or similar, chipped back and cleaned |
| C1 | Large core | Relatively undisturbed soil core, ≥30 mm diameter |
| C2 | Small core | Relatively undisturbed soil core, <30 mm diameter |
| A | Auger | Hand or mechanical auger, including post-hole diggers |
- A samples cannot be used to reliably determine soil structure due to the degree of disturbance.
- Combined sampling is common in field mapping; for example, small pit excavation to ~50–75 cm followed by augering to a required depth in relatively well-understood landscapes. Record each method used and the depth at which the method changed (e.g. P2/A (75 cm)).
- Gouge-style augers used in soft marine sediments may be included in C1 even though they may narrow to < 30 mm at their maximum depth.
- Short C2 sized samplers are common in paddock-scale monitoring and research, where they are used for rapid surface measurement. These are not generally suitable for mapping because they cannot sample below the topsoil.
Further discussion of appropriate tools for soil profile exposure can be found in Section A.1, and methods in Section C.1.
9.2.8 Depth of observation
Record the maximum depth of observation from the soil surface in whole centimetres. This depth does not necessarily need to be recorded in the field because it can be determined from the lower depth of the last horizon in the profile description.
A full profile description ideally extends to bedrock or underlying geological material, but such materials may not always be accessible with the equipment and time available. More commonly, reaching the C horizon (Section 18.1) is the deepest practically achievable goal. The minimum depth of observation for most applications in New Zealand, where possible, is 100 cm. Classification systems like the New Zealand Soil Classification and the LUC (Lynn et al. 2009) rely on ruling out certain soil features within that depth range, as well as positively identifying others.
When the target depth cannot be achieved, record the reason for stopping early using the codes in Table 9.4.
| Code | Name | Description |
|---|---|---|
| B | Bedrock | Underlying fresh rock mass encountered; no more soil or weathering substrate to describe |
| R | Resistance | Materials too difficult to extract with available equipment |
| C | Collapse | Excavation unstable or unsafe due to, for example, wetness or loose particle packing |
| W | Water | Excavation reached the water-table and cannot extract saturated material from below |
| I | Identified | The depth required to confirm a target parameter of interest was reached |
| O | Other | Circumstances unrelated to the soil itself caused early stoppage |
9.3 Setting
With the reference data established, the next task is to describe the profile’s location in relation to its setting. As noted in earlier chapters, some of these parameters can be recorded remotely or after fieldwork, by referring to notes and photographs. Further measurements are taken when observing the land surface (Chapter 10).
9.3.1 Location
Location coordinates are captured as reference data (Section 9.2.3). For routine and detailed descriptions, record elevation in metres along with expected error, and record the sensor or data source used to obtain location and elevation data using Table 2.1 and Table 2.2, respectively. If the equipment in use does not estimate expected error automatically, estimate it manually.
For example: use 1586090E, 5405722N ± 3 GS (462 ± 5 m A) for a location obtained using a smartphone, and an elevation measured with a calibrated altimeter.
When establishing a monitoring location, record additional data relevant to relocating it during future visits, as described in Section 2.2.
9.3.2 Geomorphology
Record the landscape using a code from Table 3.2. If relevant, record any significant structural control on the landscape using Table 3.7.
Record the landform using a code from Table 3.4. For detailed descriptions, record the landform’s slope and orientation as median and range in whole degrees. This is optional for routine descriptions.
For detailed descriptions, record the landform element’s morphology according to Section 3.3.2.3.
For example: use Te Fn Sl for a profile description made on the side of a low-angle fan at the back of a terrace.
9.3.3 Parent material
For rapid descriptions, record the dominant lithology as rock type at the profile (i.e. the rock type comprising the parent materials of the fine earth, as well as any profile stone) using a rock type code from Table 4.1. If in doubt, use a rock composition code. For clastic sedimentary rocks, record any relevant modifiers using the codes in Table 4.2.
If subsolum material is encountered in the profile and its dominant lithology is not the same as the profile lithology, record it separately.
Record the parent material origin code (Table 11.7) for the materials encountered, again recording separately if the solum and subsolum contrast.
For example: use RHYL Tp for a landform blanketed in rhyolitic tephra.
For routine and detailed descriptions, parent material lithology and origin are recorded on a per-horizon basis – see Section 11.8.
9.3.4 Climate and weather
For rapid descriptions, record the current weather using a code from Table 5.2, and record the air temperature (this may be estimated).
For routine descriptions, also record recent rainfall using a code from Table 5.3. If possible, for detailed descriptions record the number of days since the last rainfall event and the total mm in the previous 24 hours.
For example: use SU 21°C, NW for fine weather with no rainfall in the previous week.
9.3.5 Biota
The LCDB cover class is sufficient for rapid vegetation description (see Section 7.1).
For routine descriptions, record the dominant LUC vegetation class. For detailed descriptions, complete a separate RECCE description (see Section 6.1).
For example: use fP for a profile description made in a podocarp forest.
Direct assessment of earthworm presence in the topsoil is sometimes desired (Shepherd 2000; Shepherd and Janssen 2000). If so, record the number of earthworms observed in a ~20 cm cube of topsoil. Convert the count to a rate per square metre as \(25 × n\). Accurate counts require moist soil conditions (Schon et al. 2023).
9.3.6 Land cover, use, and management
Record the land cover at the profile using one of the LCDB cover classes (see Section 7.1).
Record the main land use using the NZLUM classification (see Section 7.2), to at least level 2 for rapid descriptions.
For routine or detailed descriptions, record to level 3. Ancillary land uses may also be recorded if they are impacting the soil profile.
For example: use 2.7.3 for a profile description made in a paddock on a dairy farm that is regularly receiving waste water.
Prior land uses may be recorded if they are known and are considered to have been capable of affecting the profile (e.g. cropping prior to vineyard conversion). Time since land-use change should also be recorded.
Land management activities (current and past, where known) should be noted in free text when they are considered to be affecting the soil profile. Minimise the use of jargon and clearly separate information on current and past land uses.
For example: in an orchard recently converted from sheep pasture, use 33, 2.4.1 (previous 2.2.3), Drip irrigation, manual control, installed and planted 2022. Originally cleared 1920, other previous management details unknown.