soil

Maps of Fundamental Soil Layers

This page has links to maps that you can view showing a range of soil attributes that are useful to farmers. These maps are derived from the dominant soils depicted in the 1:63 360/1:50 000 scale NZ Fundamental Soil Layers either from reference to analytical results stored in the National Soils Database (NSD) or as professional estimates by pedologists acknowledged as authorities in the soils of the region in question.

Instructions to see maps. Click on the 'View Map' link of the attribute you want to see mapped.

Interpreting the maps. Most of the maps show the most likely (ie modal) value from classed soil attribute data. Even within small areas of the same soil, soil attributes can be very variable. You can click on a soil area to see our estimate of the range of values that might be expected for each soil. Since it is quite impractical to measure soil attributes for all soils, we also provide a guide to the technique we used to derive our estimate. These range from measured indicating the the mapped soil has been measured, to general inference indicating that the soil that was measured was generally similar to the mapped soil, but that we have no actual measurements to support the inference.

Chemistry | Physics | Drainage | Environment | Moisture | References

Soil Classification

  • NZSC:  View map
    View a map of all of the soils of New Zealand classified according to the New Zealand Soil Classification (NZSC).

Soil Chemical attributes

The dominant soil for land area is classified according to the following key soil chemical attributes; minimum pH, maximum salinity, cation exchange capacity, total carbon, phosphate retention.

  • Minimum pH:  View map
    The classes originate from Parfitt (1984)r, and are described more fully in Webb and Wilson (1995)r. pH classes and their corresponding values are described in relation to plant growth at 0.2–0.6 m depth. Related to soil pH are nutrient availability and aluminium toxicity.
  • Maximum Salinity:  View map
    Salinity is measured at 0.0-0.6 m depth as percent soluble salts (g/100g soil). Salinity classes are described more fully in Webb and Wilson (1995)r and Milne et al. (1991)r. Salinity affects crop growth and soil slaking.
  • Cation Exchange Capacity:  View map
    Cation Exchange Capacity (CEC) is estimated as weighted averages for the soil profile from 0–0.6 m depth and expressed in units of centimoles of charge per kg (cmoles (+)/kg). The CEC classes are described more fully in Webb and Wilson (1995)r and Blakemore et al. (1987)r. CEC can affect the capacity for effluent absorption and the soil buffering capacity.
  • Total Carbon:  View map
    Total carbon (organic matter content) is estimated as weighted averages for the upper part of the soil profile from 0–0.2 m depth, and expressed as a percentage. The classes are described more fully in Webb and Wilson (1995)r and Blakemore et al. (1987)r. Carbon is important for soil structural stability and workability.
  • Phosphate Retention:  View map
    Phosphate retention (P retention) is estimated as weighted averages for the upper part of the soil profile from 0–0.2 m depth, and expressed as a percentage. The classes are described more fully in Blakemore et al. (1987)r and Webb and Wilson (1995)r. Phosphate retention values influence phosphate fertiliser requirements and soil structural stability.

Soil Physical Characteristics

The dominant soil for land areas is classified according to the following key soil physical characteristics; topsoil gravel content, rock outcrops and surface boulders, and particle size

  • Topsoil Gravel Content:  View map
    The classes originate from and are described more fully in Webb and Wilson (1995)r. The amount of stoniness affects workability and root penetrability of the soil.
  • Rock outcrops and surface boulders:  View map
    This collection of fields is an expression of the percentage of the area of the map units covered by rock outcrops or surface boulders. The classes originate from and are described more fully in Webb and Wilson (1995)r. Rock outcrops act as a hindrance to machinery and constrain other management practices.
  • Particle Size:  View map
    The classes are described in Webb and Wilson (1995)r. Particle size class describes in broad terms the proportions of sand, silt and clay in the fine earth fraction of the soil except in the case of skeletal soils ( > 35% coarse fraction ) where it applies to the whole soil. Particle size is important for soil trafficability, soil workability and moisture storage capacity and permability.

Soil Drainage Parameters

Land areas are classified according to key soil drainage parameters relevant to plant growth; potential rooting depth, depth to a slowly permeable horizon, internal soil drainage, and soil permeability.

  • Potential rooting depth:  View map
    Potential rooting depth describes the depth (in metres) to a layer that may impede root extension. Such a layer may be defined by penetration resistance, poor aeration or very low available water capacity. These classes, are described in Webb and Wilson (1995)r. Potential rooting depth can be important for plant growth and soil workability.
  • Soil Permeability:  View map
    Soil Permability is described as a class. Profile permability classes are determined in the soil profile below the A horizon by measuring hydraulic conductivity or by field measurement methods of Griffiths (1985r, 1991r). Soil permability is important forease of drainage, risk of water logging, effluent absorption potential, leaching and water loss hazards
  • Depth to a Slowly Permeable Horizon:  View map
    Depth to a slowly permeable horizon describes the depth (in metres) to a horizon in which the permeability is less than 4mm/hr as measured by techniques outlined in Griffiths (1985)r. If no slowly permeable horizon is observed, the sooil is allocated a null value is entered into the data fields. These classes, are described more fully in Webb and Wilson (1995)r. Permability is important for ease of drainage, risk of water logging, effluent absorption potential, leaching and water loss.
  • Internal Soil Drainage:  View map
    Internal soil drainage is described as a class. Drainage classes are assessed either using criteria of soil depth and chroma, or from reference to diagnostic horizons.Drainage classes used here are the same as those used in the NZ Soil Classification (Hewitt 1993)r, and outlined by Milne et al. (1995)r. Soil drainage is important for the supply of oxygen to the plant root zone, waterlogging and water drainage.

Soil Environment Parameters

Land areas are classified according to two key soil physical attributes; flood return interval and soil temperature regime (0.3 m depth).

  • Flood return interval:  View map
    The classes are described more fully in Webb and Wilson (1995)r. Frequency of flooding is important for most land activites.
  • Soil temperature regime:  View map
    The soil temperature regime relates to the soil temperature (ºC)at 0.3 m depth. The classes used originate from and are described more fully in Webb and Wilson (1995)r, which in turn is based on the work of Aldridge (1982r, 1984)r and Aldridge and Cook (1983)r. Soil temperature affects crop suitability and yield.

Soil Moisture Properties

Land areas are classified according to four key soil physical attributes: profile total available water, profile readily available water, macroporosity 0–0.6 m depth and macroporosity 0.6–0.9 m depth.

  • Profile Total Available Water:
    Profile total available water for the soil profile to a depth of 0.9 m, or to the potential rooting depth (which ever is the lesser). Values are weighted averages over the specified profile section (0–0.9 m) and are expressed in units of mm of water. The classes originate from the work of Gradwell and Birrell (1979)
    r, Wilson and Giltrap (1982)r and Griffiths (1985)r, and are described more fully in Webb and Wilson (1995)r. Profile total available water is important for droughtiness and overall water availability.
  • Profile Readily Available Water:
    Profile readily available water for the soil profile to a depth of 0.9 m, or to the potential rooting depth (whichever is the lesser). Values are weighted averages over the specified profile section (0–0.9 m) and are expressed in units of mm of water. The classes originate from the work of Gradwell and Birrell (1979)r, Wilson and Giltrap (1982)r and Griffiths (1985)r, and are described more fully in Webb and Wilson (1995)r. Profile total available water is important for droughtiness and plant available water.
  • Macroporosity (0–0.6 m):  View map
    Macroporosity is an expression of the air-filled porosity of the soil at ‘field capacity’. Values are minimum values over the specified profile section (0–0.6 m), and are expressed as a percentage of the soil volume. The classes originate from the work of Gradwell (1960)r and Gradwell and Birrell (1979)r, and are described more fully in Webb and Wilson (1995)r. Supply of oxygen to plant roots, waterlogging and ease of drainage.
  • Macroporosity (0.6–0.9 m):  View map
    Macroporosity is an expression of the air-filled porosity of the soil at ‘field capacity’. Values are minimum values over the specified profile section (0.6–0.9 m), and are expressed as a percentage of the soil volume. The classes originate from the work of Gradwell (1960)r and Gradwell and Birrell (1979)r, and are described more fully in Webb and Wilson (1995)r. Supply of oxygen to plant roots, waterlogging and ease of drainage at depth in the soil profile.

References

Aldridge, R. 1982: The prediction of soil temperature in New Zealand and application to temperature regimes of Soil Taxonomy. New Zealand Soil Bureau Scientific Report 54. 23p.
Aldridge, R.; Cook, F. J. 1983: Estimation of soil temperatures at 0.1 m and 0.3 m depths. New Zealand Soil Bureau Scientific Report 62. 18p.
Aldridge, R. 1984: Proposal for New Zealand soil temperature regimes. New Zealand Soil Bureau Soil Resources Report SR4. 12p.
Blakemore, L. C.; Searle, P. L.; Daly, B. K. 1987: Methods for chemical analysis of soils. New Zealand Soil Bureau Scientific Report 80. 103p.
Gradwell, M. W. 1960: Changes in the pore space of a pasture topsoil under animal treading. New Zealand Journal of Agricultural Research 3: 663–674.
Gradwell, M. W.; Birrell, K. S. 1979: Soil Bureau laboratory methods. Part C: Methods for physical analysis of soils. New Zealand Soil Bureau Scientific Report 10C.
Griffiths, E. 1985: Interpretation of soil morphology for assessing moisture movement and storage. New Zealand Soil Bureau Scientific Report 74. 20p.
Griffiths, E. 1991: Assessing permability class from soil morphology. DSIR Land Resources technical record. 48p
Hewitt, A. E. 1993: Methods and rationale of the New Zealand Soil Classification. Landcare Research Science Series 2, Lincoln, New Zealand, Manaaki Whenua Press. 71p.
Milne, J.D.G., Clayden, B., Singleton, P.L., Wilson, A.D. 1995: Soil description handbook. Lincoln, New Zealand, Manaaki Whenua Press. 157p.
Parfitt, R. L.1984: Reserves of nutrients in New Zealand soils. New Zealand Soil News 32: 123–30.
Webb, T. H., Wilson, A. D. 1995: A manual of land characteristics for evaluation of rural land. Landcare Research Science Series 10. Lincoln, New Zealand, Manaaki Whenua Press. 32p.
Wilson, A. D; Giltrap, D. J. 1982: Prediction and mapping of soil water retention properties. New Zealand Soil Bureau District Office Report WN7. 15p.