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Doc #26 — Soil and Agricultural Capability Map

New Zealand Soils by Region: Type, Fertility, Drainage, and Crop Suitability

Phase: 1–2 (Print Early — reference data for all agricultural planning) | Feasibility: [A] Established (reference compilation from existing NZ soil science data)

Unreliable — not for operational use. Produced by AI under human direction and editorial review. This document contains errors of fact, judgment, and emphasis and has not been peer-reviewed. See About the Recovery Library for methodology and limitations. © 2026 Recoverable Foundation. Licensed under CC BY-ND 4.0. This disclaimer must be included in any reproduction or redistribution.

EXECUTIVE SUMMARY

Emergency cropping on wrong soils fails; fertiliser applied to non-responsive soils is wasted; without soil capability data, agricultural expansion decisions destroy scarce inputs and produce crop failures. New Zealand’s soils are among the most diverse per unit area of any country, a consequence of varied geology (volcanic, sedimentary, metamorphic), high rainfall gradients, active tectonism, and young landscape age. The New Zealand Soil Classification (NZSC) identifies 15 soil orders, of which eight dominate the agricultural landscape.1 Understanding which soils occur where, what they can grow, and what they lack is fundamental to every agricultural decision in this library — from emergency crop expansion (Doc #75) to soil fertility management without imports (Doc #80) to pastoral farming under nuclear winter (Doc #74).

This document provides a region-by-region reference to NZ’s dominant soil types, their agricultural characteristics, and crop suitability under both normal and nuclear winter conditions. It is designed to be used alongside the Land Use Capability (LUC) classification system, which rates NZ land on an eight-class scale from Class I (most versatile) to Class VIII (unsuitable for productive use).2

Key points for agricultural planners:

Contents

COMPUTED DATA: SOIL AND AGRICULTURAL DATA

View the Soil Data Tables → — Regional soil summaries, NZSC orders, LUC classes, fertiliser requirements, crop suitability, and a land capability map.

View the generation script → — Python source code and data sources (Manaaki Whenua, LRIS Portal).

1. THE NEW ZEALAND SOIL CLASSIFICATION: OVERVIEW

The NZSC, developed by Manaaki Whenua — Landcare Research, classifies NZ soils into 15 orders based on properties that reflect their formation processes and agricultural behaviour.7 The eight orders most relevant to agricultural planning are described below, from most to least agriculturally favourable in general terms. The remaining seven orders (Anthropic, Granular, Melanic, Oxidic, Semi-Arid, Ultic, Raw) are either rare in agricultural settings or geographically restricted.

The primary data sources for NZ soil mapping are S-map (the national digital soil map) and the Land Resource Information System (LRIS Portal), both maintained by Manaaki Whenua — Landcare Research.8 These digital resources should be printed in summary form while printing infrastructure is available — they represent decades of field survey work that cannot be replicated quickly.

2. MAJOR SOIL TYPES BY REGION

2.1 Allophanic Soils

Where: Waikato, Bay of Plenty, Taranaki, parts of southern Auckland. Formed from volcanic ash (tephra) deposited by eruptions from the Taupo Volcanic Zone and Taranaki.9

Properties: Deep, well-structured, free-draining, dark topsoils with high organic matter. The allophane clay mineral gives these soils exceptional physical properties — they resist compaction, drain freely, yet retain adequate moisture for plant growth. Natural fertility is moderate to high. Soil pH typically 5.5–6.5.10

Agricultural capability: Among NZ’s best soils. Support intensive dairy pasture, maize, horticulture (kiwifruit in Bay of Plenty), potatoes, and all temperate vegetables. LUC Class I–III where topography is gentle.11

Limitations: Moderate phosphorus retention — allophane binds phosphorus strongly, requiring higher application rates to maintain plant-available P levels. This is manageable with superphosphate (while available) but means that phosphorus “locked up” in these soils is less accessible to plants than in other soil types.12 Under nuclear winter, these soils warm relatively quickly in spring (free-draining soils warm faster than wet soils), which is an advantage.

Management without imported fertiliser: Maintain soil pH with lime (domestically available). Legume-based rotations for nitrogen (Doc #80, Section 2.4). Prioritise bone meal and compost for phosphorus — though both supply phosphorus at substantially lower concentrations than superphosphate (bone meal contains 10–15% P₂O₅ vs. 9% for single superphosphate, but requires larger volumes due to slower release; compost typically contains only 0.5–1.5% P₂O₅), requiring much larger application volumes per hectare. These soils’ high P-retention means that phosphorus builds slowly but is also lost slowly. Cobalt supplementation for livestock may be needed — allophanic soils derived from rhyolitic tephra can be cobalt-deficient, though less severely than pumice soils.13

2.2 Recent Soils

Where: River flats and floodplains throughout NZ — notably the Canterbury Plains, Manawatu, Wairarapa, Hauraki Plains, Waikato river terraces, and Southland plains.14

Properties: Young soils formed from alluvium deposited by rivers. Typically well-drained to moderately well-drained, with variable texture depending on parent material (sandy near rivers, silty further from channels). High natural fertility where alluvium is derived from fertile catchments. Soil structure is weak (young soils have not developed strong aggregation).15

Agricultural capability: Excellent for cropping — flat, fertile, workable. Canterbury’s recent soils are the foundation of NZ’s arable industry (wheat, barley, ryegrass seed, vegetable seed). LUC Class I–II on well-drained flats.16

Limitations: Flood risk on active floodplains — this is the tradeoff for the fertility that periodic flooding delivers. On Canterbury’s stony recent soils, drainage can be excessive, leading to drought stress during dry periods. Some Canterbury recent soils are shallow over gravels, limiting root depth and water-holding capacity.17

Management without imported fertiliser: These soils respond well to compost and manure applications because their weak structure benefits from organic matter addition. Legume rotations are essential on cropping land (Doc #80). Flood risk must be factored into crop placement — do not plant the season’s entire potato crop on floodplain land.

2.3 Brown Soils

Where: The most widespread soil order in NZ — found on hill country and downlands across both islands. Common in Southland, Otago, Wairarapa, Manawatu hill country, Marlborough, Nelson, and throughout the South Island foothills.18

Properties: Highly variable. Formed under forest or tussock grassland on a range of parent materials (sandstone, mudstone, greywacke, schist, loess). Typically moderately well-drained with moderate fertility. Soil pH 5.0–6.0 (often acid). Structure varies from good (on harder parent materials) to weak (on soft sedimentary rocks).19

Agricultural capability: Predominantly pastoral — sheep and beef grazing on hill country. Lowland brown soils support cropping where topography allows. LUC Class III–VI depending on slope and drainage.20

Limitations: Fertility is moderate and variable. Many brown soils on hill country are shallow, stony, or steep, limiting options to permanent pasture. Aluminium toxicity can occur at low pH (below 5.2), inhibiting root growth — liming is essential on acid brown soils.21

Management without imported fertiliser: Lime is the highest priority input. Maintaining clover in pastures (for nitrogen fixation) requires pH above 5.5 (Doc #80, Section 5.3). On flatter brown soils used for cropping, standard legume rotations apply. On hill country, maintain pastoral use — these soils are generally not suitable for emergency crop expansion due to slope.

2.4 Pallic Soils

Where: Canterbury Plains (eastern portions), Hawke’s Bay, parts of Wairarapa, Marlborough, North Otago. Formed from loess (wind-blown silt) deposits, often over gravels.22

Properties: Silty texture, moderate fertility, pale subsoils (hence “pallic”). Distinctive fragipan (dense, hard subsoil layer) in many profiles restricts root penetration and drainage. Drainage is impeded — winter waterlogging is common, but summer drought occurs because the shallow root zone dries quickly. A soil of contradictions: too wet in winter, too dry in summer.23

Agricultural capability: Canterbury’s pallic soils are widely cropped, but irrigation was increasingly necessary pre-event to overcome summer drought. Without irrigation (which depends on electricity — available under the baseline scenario — and on pump, pipe, and pivot-irrigator maintenance requiring bearings, seals, and drive components that are currently imported), cropping yields on pallic soils decline 20–40% in dry years compared to irrigated production.24 LUC Class II–IV.25

Limitations: Drought-prone in summer. Winter waterlogging limits early spring cultivation (the soil is too wet to work). The fragipan layer restricts root depth and drainage. Under nuclear winter, reduced evaporation (cooler temperatures) may ease summer drought but worsen winter waterlogging. These soils warm slowly in spring — expect delayed planting compared to lighter soils.26

Management without imported fertiliser: Moderate natural fertility means less fertiliser dependence than some other soils, but cropping still depletes nutrients. Organic matter addition (compost, green manure) is particularly valuable because it improves the soil’s poor physical structure, increasing water infiltration and root penetration through the fragipan zone. Drainage maintenance (tile drains, open ditches) is essential — neglected drainage on pallic soils leads to rapid productivity decline.

2.5 Pumice Soils

Where: Central North Island — Taupo district, Rotorua, parts of Bay of Plenty, Waikato margins. Formed from rhyolitic pumice deposits, primarily from the Taupo eruption (~232 CE) and earlier events.27

Properties: Very free-draining (almost excessively so), light, low bulk density. Low natural fertility — pumice weathers slowly and releases few nutrients. Notably deficient in cobalt, selenium, and often phosphorus. Soil pH 5.5–6.5. Organic matter accumulation is slow due to rapid drainage.28

Limitations: The defining limitation is nutrient poverty. Pre-event, productive farming on pumice soils required heavy fertiliser inputs plus cobalt and selenium supplementation for livestock. Without these inputs, livestock on pumice soils develop cobalt deficiency (causing wasting disease in sheep and cattle) and selenium deficiency (white muscle disease in lambs, reduced fertility in ewes).29 Crops grown on unfertilised pumice soils yield poorly.

Agricultural capability: Under full fertiliser regimes, pumice soils support productive dairy and sheep farming and some forestry. Without imports, agricultural capability reverts toward the low productivity that characterised these soils before aerial topdressing began in the 1950s. LUC Class IV–VI for agriculture; many areas revert to low-productivity pastoral or forestry use.30

Management without imported fertiliser: This is one of the most challenging transitions. Cobalt supplementation for livestock is critical — without it, stock health on pumice soils deteriorates over months as liver cobalt reserves deplete, progressing to clinical deficiency (wasting, failure to thrive) within 3–6 months on severely deficient pastures.31 NZ may have limited cobalt sources (small deposits have been identified, though none are currently mined commercially).32 Biochar application (Doc #80, Section 6.4) improves nutrient and water retention on pumice soils, though biochar’s cation exchange capacity (typically 40–80 cmol/kg) is lower than that of the allophane clays found in better volcanic soils, and application rates of 5–20 tonnes/ha are needed to materially change soil behaviour — requiring substantial charcoal production capacity (Doc #102). Heavy composting and legume-based pastures are essential. Realistic expectation: productivity on pumice soils declines substantially without imports — an estimated 40–60% below pre-event levels, based on the historical productivity of these soils before aerial topdressing began in the 1950s.33

2.6 Gley Soils

Where: Lowland areas with high water tables — Hauraki Plains, Manawatu lowlands, parts of Southland, West Coast. Anywhere flat land meets poor natural drainage.34

Properties: Poorly drained to very poorly drained. Grey or blue-grey subsoils (the “gleyed” colour indicates permanent waterlogging). High clay content. Potentially high natural fertility where nutrient-rich sediments have accumulated, but waterlogging limits root growth and restricts the range of crops that can be grown.35

Agricultural capability: Under drained conditions, gley soils can be highly productive — the Hauraki Plains and parts of the Manawatu are productive dairy country only because of extensive artificial drainage (tile drains, open ditches, pump stations). Without drainage maintenance, these soils revert to wetland. LUC Class III–V when drained; Class VI–VIII when undrained.36

Limitations: Entirely dependent on drainage infrastructure. NZ has approximately 150 agricultural drainage pump stations, most electrically powered (electricity available under the baseline scenario), but these stations also require mechanical maintenance — pump impellers, bearings, seals, and motor windings degrade and require replacement parts that are currently imported.37 Tile drain systems require periodic rodding and repair. Under nuclear winter, higher rainfall and reduced evaporation in some regions could worsen waterlogging. Gley soils are cold and slow to warm in spring — their high water content gives them high thermal mass, requiring more solar energy to raise temperature than lighter, drier soils.38 They cannot be cultivated when wet without severe structural damage (compaction, smearing).

Management without imported fertiliser: If drainage is maintained (electricity for pumps is available under baseline scenario), these soils can continue in pastoral production with standard fertility management. Cropping is risky — narrow cultivation windows and flood/waterlogging risk make gley soils poor candidates for emergency crop expansion. Maintain as dairy pasture where drainage works.

2.7 Organic Soils

Where: Hauraki Plains, Southland, Waikato margins, scattered wetland areas. Formed from accumulated plant material (peat) in former wetlands.39

Properties: Very high organic matter (>30% organic carbon). Dark, spongy when wet, shrink and crack when dry. Naturally very poorly drained. When drained for agriculture, organic soils subside (shrink and compact) over decades — the Hauraki Plains have subsided by up to 3 metres since drainage began in the early 1900s.40

Agricultural capability: When drained, organic soils can be very productive for pastoral farming due to high inherent nutrient content. Some vegetable production (onions, potatoes) on Hauraki Plains peat. LUC Class III–IV when drained and managed; Class VIII when undrained.41

Limitations: Subsidence is progressive and irreversible — drained peat soils lose elevation over decades, eventually requiring more intensive pumping to maintain drainage. Fire risk when dry. Structural damage from heavy machinery. Nutrient availability is sometimes paradoxically low despite high organic matter content — the organic forms of nitrogen and phosphorus must be mineralised (broken down by soil organisms) before plants can use them, and this process is slow in cold, wet conditions.42

Management without imported fertiliser: These soils have high reserves of organic nitrogen and phosphorus that become available over time through natural mineralisation — less dependent on external nutrient inputs than mineral soils. Maintain drainage. Avoid overstocking, which compacts the soft peat surface. Good candidates for continued pastoral production without heavy fertiliser inputs.

2.8 Podzol Soils

Where: West Coast of the South Island, parts of Northland, high-rainfall areas of Southland and Stewart Island. Formed under native forest in high-rainfall environments.43

Properties: Strongly leached and acidic (pH 4.0–5.0). Distinctive bleached horizon below the topsoil where iron, aluminium, and organic matter have been washed downward (podzolised). Very low natural fertility. Often gravelly or sandy.44

Agricultural capability: Very limited. The West Coast’s podzol soils support some pastoral farming where heavily fertilised, but without fertiliser inputs they are among NZ’s least productive agricultural soils. LUC Class V–VII for agriculture. Most West Coast agricultural land is better suited to forestry.45

Limitations: Extreme acidity, aluminium toxicity, low phosphorus availability, low nutrient reserves, poor structure. Heavy liming is required even to establish productive pasture. Under nuclear winter, the West Coast’s already high rainfall and cool temperatures make these soils even less viable for cropping.

Management without imported fertiliser: Heavy liming (lime is domestically available) to raise pH above 5.5 is the minimum requirement — typical application rates of 5–8 tonnes/ha for initial correction, with 1–2 tonnes/ha maintenance every 3–5 years.46 Even with lime, productivity remains 50–70% below that of better soils without phosphorus inputs, because liming corrects acidity but does not supply the phosphorus and other nutrients these soils inherently lack. Realistic assessment: West Coast podzol soils revert largely to forestry and very low-intensity grazing. These are not priority areas for food production under trade isolation.

3. LAND USE CAPABILITY CLASSIFICATION

The LUC system, administered by Manaaki Whenua — Landcare Research, classifies all NZ land into eight classes based on physical limitations for sustained productive use.47 This classification is the standard planning tool for land allocation decisions.

LUC Class Description Approximate NZ area (ha) Suitability under trade isolation
I Few limitations; suitable for all uses including intensive cropping ~180,000 Priority for arable food production
II Slight limitations; suitable for cropping with minor management ~900,000 Cropping and intensive pastoral
III Moderate limitations; suitable for cropping with careful management ~1,400,000 Cropping where soil and climate allow
IV Significant limitations; occasional cropping, primarily pastoral ~2,800,000 Pastoral; cropping only in favourable seasons
V Unsuitable for cropping; pastoral, forestry ~700,000 Low-intensity pastoral, forestry
VI Unsuitable for cropping; pastoral with limitations, forestry ~5,300,000 Extensive pastoral, forestry
VII Severe limitations; protection forestry, limited grazing ~5,900,000 Forestry, conservation
VIII Unsuitable for production; conservation ~6,500,000 Conservation; no agricultural use

Areas are approximate, derived from NZ Land Resource Inventory data.48

Key planning implications: NZ has approximately 2.5 million hectares of LUC Class I–III land — the land that can sustain arable cropping. Of this, roughly 700,000–1,000,000 hectares is currently in pastoral use and could be converted to cropping under emergency conditions (Doc #75).49 Under normal yields, the total exceeds what is needed to feed 5.2 million people, though nuclear winter yield reductions of 30–50% (Doc #74) reduce the margin considerably. The binding constraint is not total land area but rather the specific combination of soil, climate, seed availability, machinery, and skilled labour in each region.

4. CROP SUITABILITY BY REGION

4.1 Normal conditions

Region Dominant soils Best-suited crops Key limitations
Northland Brown, Ultic Kumara, maize, subtropical fruit, pasture Summer drought on eastern soils; acid soils
Waikato Allophanic, Recent, Organic Maize, potatoes, dairy pasture, kiwifruit Phosphorus retention (allophanic); drainage (gley/organic)
Bay of Plenty Allophanic, Pumice Kiwifruit, avocado, maize, pasture Pumice nutrient deficiency on margins
Taupo / Central Plateau Pumice Pastoral (with supplements), forestry Cobalt/selenium deficiency; frost
Taranaki Allophanic Dairy pasture, maize (limited) Steep topography limits cropping
Manawatu / Whanganui Brown, Recent, Gley Cereals, vegetables, dairy pasture Hill country limits to pastoral; drainage on lowlands
Hawke’s Bay Pallic, Recent Pip fruit, wine grapes, cereals, vegetables Summer drought; wind erosion on pallic soils
Wairarapa Brown, Pallic, Recent Pastoral, cereals, wine grapes Summer drought; limited flat land
Canterbury Pallic, Recent, Brown Wheat, barley, ryegrass seed, potatoes, vegetables Summer drought without irrigation; stony soils
West Coast Podzol, Gley Pastoral (limited), forestry Extreme rainfall; acid soils; low fertility
Otago Brown, Pallic, Semi-Arid Stone fruit, wine grapes, cereals, pastoral Frost; drought (Central Otago); limited growing season
Southland Brown, Gley, Organic Pastoral (dairy, sheep), oats, swedes Cool climate; waterlogging; short growing season

4.2 Nuclear winter adjustments

Under 3–5 degrees C of cooling and 10–30% reduced sunlight (Doc #74), the crop suitability map shifts materially:50

Region Nuclear winter suitability Notes
Northland Becomes NZ’s most favourable cropping region. Potatoes, brassicas, cereals viable. Reduced frost pressure advantage over southern regions increases
Waikato / Bay of Plenty Remains productive for potatoes, brassicas, oats. Maize marginal. Allophanic soils warm faster than heavy soils — advantage
Central Plateau Pastoral only. Cropping infeasible due to frost and short season. Focus on livestock with cobalt/selenium management
Canterbury Growing season compresses significantly. Spring wheat and barley remain viable. Late-maturing crops (maize) not viable. Potatoes marginal in cooler years. Irrigation demand reduces (cooler, less evaporation) — partially offsets yield decline
Southland Growing season compresses severely. Oats, swedes, brassicas viable. Cereals marginal. Waterlogging worsens with reduced evaporation
West Coast Minimal agricultural contribution under nuclear winter. Maintain forestry and very limited pastoral

5. CRITICAL NUTRIENT DEFICIENCIES BY REGION

NZ soils have well-documented nutrient deficiencies that, under normal conditions, are corrected with imported supplements. Under trade isolation, these deficiencies become harder to manage.51

Deficiency Affected regions / soils Consequence Available NZ mitigation
Phosphorus Nearly all NZ soils Reduced pasture and crop growth Superphosphate from existing stocks and NZ phosphate rock (Doc #80); bone meal; compost
Cobalt Pumice soils (Central North Island) Wasting disease in sheep and cattle; failure to thrive Limited NZ cobalt sources; seaweed may contain trace cobalt; concentrate livestock on non-pumice soils where possible
Selenium Widespread, especially volcanic soils White muscle disease in lambs; reduced fertility NZ has no significant selenium source. Mitigate through dietary diversity (selenium concentrates in fish, offal) and by concentrating breeding stock on higher-selenium soils
Boron Some Waikato and Bay of Plenty soils Hollow heart in brassicas; reduced seed set Small NZ boron deposits may exist; otherwise unmitigated
Molybdenum Acid soils (widespread) Impaired nitrogen fixation in legumes Corrected by liming (molybdenum availability increases with pH)
Sulphur Leached soils distant from coast Reduced pasture growth, especially clover NZ geothermal sulphur (Doc #113); superphosphate contains sulphur

6. SOIL MANAGEMENT PRIORITIES UNDER TRADE ISOLATION

6.1 Protect LUC Class I–III land

NZ’s approximately 2.5 million hectares of versatile land is a finite, irreplaceable resource. Decisions made in the first year about land allocation (Doc #75) determine food production capacity for decades. Key principles:

  • Do not convert good cropping land to non-agricultural use.
  • Do not allow soil structural damage from working wet soils — one season of compaction can take years to correct.
  • Maintain drainage infrastructure on all productive lowland soils.
  • Prioritise lime application to cropping soils to sustain biological nitrogen fixation (Doc #80, Section 5).

6.2 Match crops to soils

The crop suitability tables in Section 4 are guides, not prescriptions. Local soil knowledge — held by farmers, regional council staff, and fertiliser company agronomists — is more precise than any national-scale document. The regional agricultural advisers recommended in Doc #75 should use S-map data (while accessible digitally) and local knowledge to match crops to the specific soils on each farm.

6.3 Soil testing

NZ has commercial soil testing laboratories (Hill Laboratories, Hamilton; Eurofins, various locations) that should continue operating as essential services.52 Regular soil testing — at minimum pH, Olsen P, exchangeable K, and organic matter — provides the data for adaptive management of declining soil fertility. Without testing, fertility management is guesswork. Soil testing consumes modest resources (chemical reagents, laboratory equipment, electricity) and returns disproportionate value in targeted, efficient fertiliser use.

7. DATA SOURCES AND LIMITATIONS

S-map (Manaaki Whenua — Landcare Research): NZ’s most detailed digital soil map, with property data for each soil type including drainage class, texture, depth, and nutrient status. Coverage is incomplete — approximately 45% of NZ’s land area is mapped in S-map at detailed scale as of 2025, with the remainder covered at reconnaissance scale through the older New Zealand Land Resource Inventory (NZLRI).53 Priority regions for agricultural planning (Canterbury, Waikato, Hawke’s Bay) have relatively complete S-map coverage.

LRIS Portal (Land Resource Information System): The public access point for spatial soil and land resource data, including LUC maps, soil maps, and climate data layers.54

Limitation: Both S-map and the LRIS Portal are digital systems. Their data should be extracted, summarised, and printed for the regions of highest agricultural importance while computing and printing infrastructure are available. A full print of the national soil map at useful resolution would require thousands of A3 sheets — printing regional summaries for the priority cropping regions identified in Doc #75 is more realistic and should be among the first reference data printed (Doc #29).

8. CROSS-REFERENCES

Document Relationship
Doc #74 — Pastoral Farming Under Nuclear Winter Pasture productivity by region depends on soil type and fertility
Doc #75 — Cropping and Dairy Adaptation Emergency crop expansion must target appropriate soils; this document provides the soil basis for land allocation
Doc #76 — Emergency Crop Expansion Region-specific planting guidance depends on soil capability
Doc #80 — Soil Fertility Without Imports Companion document — covers nutrient management strategies for the soils described here
Doc #16 — NZ Topographic and Infrastructure Atlas Physical geography context for soil distribution
Doc #18 — NZ Climate Baseline Data Climate-soil interaction determines crop suitability
Doc #22 — NZ Geological and Mineral Resource Atlas Parent material geology determines soil type; mineral resources (phosphate, cobalt) for soil amendment
Doc #79 — Geothermal Greenhouses Seaweed as trace element and potassium source for deficient soils
Doc #102 — Charcoal Production Biochar for improving pumice and sandy soils
Doc #149 — Land Use Reallocation Policy framework for allocating land based on soil capability

APPENDIX A: QUICK REFERENCE — SOIL ORDERS AND KEY PROPERTIES

Soil Order Drainage Natural Fertility pH Range Best Agricultural Use Worst Limitation
Allophanic Free-draining Moderate–high 5.5–6.5 Dairy, cropping, horticulture P retention
Recent Well-drained (variable) High (variable) 5.5–7.0 Arable cropping, intensive pastoral Flood risk; stones (Canterbury)
Brown Moderate Moderate (variable) 5.0–6.0 Pastoral (hill country); cropping (lowland) Slope; acidity; variability
Pallic Impeded Moderate 5.5–6.5 Arable cropping (with irrigation/drainage) Summer drought; winter waterlogging
Pumice Excessive Low 5.5–6.5 Pastoral (with supplements); forestry Cobalt/selenium deficiency; nutrient poverty
Gley Poor Moderate–high 5.0–6.5 Dairy pasture (when drained) Waterlogging; drainage dependence
Organic Very poor High (slow-release) 4.5–6.0 Dairy pasture; some vegetables (when drained) Subsidence; drainage dependence
Podzol Variable Very low 4.0–5.0 Forestry; very limited pastoral Extreme acidity; nutrient poverty

  1. Hewitt, A.E. (2010), “New Zealand Soil Classification,” 3rd edition, Manaaki Whenua Press. The NZSC is the national standard for soil classification in NZ, replacing the earlier NZ Genetic Soil Classification. The 15 soil orders are: Allophanic, Anthropic, Brown, Gley, Granular, Melanic, Organic, Oxidic, Pallic, Podzol, Pumice, Raw, Recent, Semi-Arid, Ultic. https://soils.landcareresearch.co.nz/↩︎

  2. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  3. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  4. Saunders, W.M.H. (1965), “Phosphate retention by NZ soils and its relationship to free sesquioxides, organic matter, and other soil properties,” NZ Journal of Agricultural Research, 8, 30–57. NZ soils are naturally low in plant-available phosphorus. Volcanic soils (allophanic, pumice) have particularly high phosphorus retention due to allophane and ferrihydrite minerals. See also Doc #80 for detailed phosphorus management.↩︎

  5. Clark, R.G. et al. (1986), “Cobalt deficiency in NZ — a review of the biology and status,” NZ Journal of Agricultural Research, 29, 1–12. Also: Oldfield, J.E. (1999), “Selenium World Atlas,” Selenium-Tellurium Development Association. NZ is recognised as selenium-deficient across most of its agricultural land. Cobalt deficiency is concentrated in pumice soils of the central North Island but can occur on some other volcanic and highly leached soils.↩︎

  6. Soil thermal properties are determined primarily by water content and bulk density. Wet soils (gley, organic) have high volumetric heat capacity (approximately 3.0–3.5 MJ/m³/°C) compared to dry, porous soils (pumice, allophanic: approximately 1.5–2.0 MJ/m³/°C). Under nuclear winter, reduced solar radiation input means these thermal differences translate into materially different spring warm-up rates. See Hillel, D. (2004), “Introduction to Environmental Soil Physics,” Academic Press, for soil thermal property fundamentals.↩︎

  7. Hewitt, A.E. (2010), “New Zealand Soil Classification,” 3rd edition, Manaaki Whenua Press. The NZSC is the national standard for soil classification in NZ, replacing the earlier NZ Genetic Soil Classification. The 15 soil orders are: Allophanic, Anthropic, Brown, Gley, Granular, Melanic, Organic, Oxidic, Pallic, Podzol, Pumice, Raw, Recent, Semi-Arid, Ultic. https://soils.landcareresearch.co.nz/↩︎

  8. Manaaki Whenua — Landcare Research maintains S-map (https://smap.landcareresearch.co.nz/) and the LRIS Portal (https://lris.scinfo.org.nz/). S-map coverage as of 2025 is approximately 45% of NZ at detailed scale. The New Zealand Land Resource Inventory (NZLRI) provides reconnaissance-level soil and land resource data for the entire country, mapped at 1:50,000 scale in the 1970s–1980s and subsequently updated.↩︎

  9. Lowe, D.J. et al. (2010), “Tephras and tephrochronology in NZ,” in “NZ Soil News,” and various publications on Waikato-Bay of Plenty soil properties. Allophanic soils form from weathering of volcanic tephra under moderate rainfall (approximately 1,200–2,500 mm/yr). Their excellent physical properties (high porosity, resistance to compaction, stable aggregation) make them among NZ’s most versatile agricultural soils.↩︎

  10. Lowe, D.J. et al. (2010), “Tephras and tephrochronology in NZ,” in “NZ Soil News,” and various publications on Waikato-Bay of Plenty soil properties. Allophanic soils form from weathering of volcanic tephra under moderate rainfall (approximately 1,200–2,500 mm/yr). Their excellent physical properties (high porosity, resistance to compaction, stable aggregation) make them among NZ’s most versatile agricultural soils.↩︎

  11. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  12. Saunders, W.M.H. (1965), “Phosphate retention by NZ soils and its relationship to free sesquioxides, organic matter, and other soil properties,” NZ Journal of Agricultural Research, 8, 30–57. NZ soils are naturally low in plant-available phosphorus. Volcanic soils (allophanic, pumice) have particularly high phosphorus retention due to allophane and ferrihydrite minerals. See also Doc #80 for detailed phosphorus management.↩︎

  13. Clark, R.G. et al. (1986), “Cobalt deficiency in NZ — a review of the biology and status,” NZ Journal of Agricultural Research, 29, 1–12. Also: Oldfield, J.E. (1999), “Selenium World Atlas,” Selenium-Tellurium Development Association. NZ is recognised as selenium-deficient across most of its agricultural land. Cobalt deficiency is concentrated in pumice soils of the central North Island but can occur on some other volcanic and highly leached soils.↩︎

  14. Soil properties of Recent soils from Hewitt (note 1) and S-map soil fact sheets. Canterbury’s recent soils are predominantly formed from greywacke alluvium — often stony, free-draining, and prone to summer drought. Waikato and Manawatu recent soils are typically finer-textured (silty) and more fertile.↩︎

  15. Soil properties of Recent soils from Hewitt (note 1) and S-map soil fact sheets. Canterbury’s recent soils are predominantly formed from greywacke alluvium — often stony, free-draining, and prone to summer drought. Waikato and Manawatu recent soils are typically finer-textured (silty) and more fertile.↩︎

  16. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  17. Soil properties of Recent soils from Hewitt (note 1) and S-map soil fact sheets. Canterbury’s recent soils are predominantly formed from greywacke alluvium — often stony, free-draining, and prone to summer drought. Waikato and Manawatu recent soils are typically finer-textured (silty) and more fertile.↩︎

  18. Brown soils are NZ’s most extensive soil order, covering approximately 45% of the country’s land area, primarily on hill country. Properties vary enormously depending on parent material, rainfall, and landscape position. See Hewitt (note 1).↩︎

  19. Brown soils are NZ’s most extensive soil order, covering approximately 45% of the country’s land area, primarily on hill country. Properties vary enormously depending on parent material, rainfall, and landscape position. See Hewitt (note 1).↩︎

  20. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  21. Brown soils are NZ’s most extensive soil order, covering approximately 45% of the country’s land area, primarily on hill country. Properties vary enormously depending on parent material, rainfall, and landscape position. See Hewitt (note 1).↩︎

  22. Pallic soils: Hewitt (note 1); also Eden, D.N. and Hammond, A.P. (2003), “Dust accumulation in the NZ region since the last glacial maximum,” Quaternary Science Reviews, 22, 2037–2052, on loess distribution. The fragipan characteristic of many pallic soils is a dense, brittle subsoil layer formed through repeated wetting and drying cycles, typically found at 40–80 cm depth.↩︎

  23. Pallic soils: Hewitt (note 1); also Eden, D.N. and Hammond, A.P. (2003), “Dust accumulation in the NZ region since the last glacial maximum,” Quaternary Science Reviews, 22, 2037–2052, on loess distribution. The fragipan characteristic of many pallic soils is a dense, brittle subsoil layer formed through repeated wetting and drying cycles, typically found at 40–80 cm depth.↩︎

  24. Pallic soils: Hewitt (note 1); also Eden, D.N. and Hammond, A.P. (2003), “Dust accumulation in the NZ region since the last glacial maximum,” Quaternary Science Reviews, 22, 2037–2052, on loess distribution. The fragipan characteristic of many pallic soils is a dense, brittle subsoil layer formed through repeated wetting and drying cycles, typically found at 40–80 cm depth.↩︎

  25. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  26. Pallic soils: Hewitt (note 1); also Eden, D.N. and Hammond, A.P. (2003), “Dust accumulation in the NZ region since the last glacial maximum,” Quaternary Science Reviews, 22, 2037–2052, on loess distribution. The fragipan characteristic of many pallic soils is a dense, brittle subsoil layer formed through repeated wetting and drying cycles, typically found at 40–80 cm depth.↩︎

  27. Pumice soils: Hewitt (note 1); also Parfitt, R.L. (1990), “Allophane in New Zealand — a review,” Australian Journal of Soil Research, 28, 343–360. Pumice weathers extremely slowly in NZ conditions, producing soils with low clay content, low nutrient reserves, and high macroporosity (rapid drainage). The cobalt deficiency of pumice soils was identified in the 1930s as the cause of “bush sickness” in livestock.↩︎

  28. Pumice soils: Hewitt (note 1); also Parfitt, R.L. (1990), “Allophane in New Zealand — a review,” Australian Journal of Soil Research, 28, 343–360. Pumice weathers extremely slowly in NZ conditions, producing soils with low clay content, low nutrient reserves, and high macroporosity (rapid drainage). The cobalt deficiency of pumice soils was identified in the 1930s as the cause of “bush sickness” in livestock.↩︎

  29. Clark, R.G. et al. (1986), “Cobalt deficiency in NZ — a review of the biology and status,” NZ Journal of Agricultural Research, 29, 1–12. Also: Oldfield, J.E. (1999), “Selenium World Atlas,” Selenium-Tellurium Development Association. NZ is recognised as selenium-deficient across most of its agricultural land. Cobalt deficiency is concentrated in pumice soils of the central North Island but can occur on some other volcanic and highly leached soils.↩︎

  30. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  31. Clark, R.G. et al. (1986), “Cobalt deficiency in NZ — a review of the biology and status,” NZ Journal of Agricultural Research, 29, 1–12. Also: Oldfield, J.E. (1999), “Selenium World Atlas,” Selenium-Tellurium Development Association. NZ is recognised as selenium-deficient across most of its agricultural land. Cobalt deficiency is concentrated in pumice soils of the central North Island but can occur on some other volcanic and highly leached soils.↩︎

  32. NZ cobalt resources: Christie, A.B. et al. (2007), “Mineral deposits of NZ,” Australasian Institute of Mining and Metallurgy Monograph 22. Small cobalt occurrences have been noted in association with nickel-bearing ultramafic rocks in Nelson and the Dun Mountain area, but no commercial cobalt mining has operated in NZ. Cobalt is also present in small quantities in some NZ iron-sand deposits.↩︎

  33. Pumice soils: Hewitt (note 1); also Parfitt, R.L. (1990), “Allophane in New Zealand — a review,” Australian Journal of Soil Research, 28, 343–360. Pumice weathers extremely slowly in NZ conditions, producing soils with low clay content, low nutrient reserves, and high macroporosity (rapid drainage). The cobalt deficiency of pumice soils was identified in the 1930s as the cause of “bush sickness” in livestock.↩︎

  34. Gley soils: Hewitt (note 1). Gley soils form where the water table is at or near the surface for extended periods. The Hauraki Plains were extensively drained for dairy farming in the early-to-mid 20th century. Maintaining this drainage requires pumping stations — NZ has approximately 150 agricultural drainage pump stations, most electrically powered.↩︎

  35. Gley soils: Hewitt (note 1). Gley soils form where the water table is at or near the surface for extended periods. The Hauraki Plains were extensively drained for dairy farming in the early-to-mid 20th century. Maintaining this drainage requires pumping stations — NZ has approximately 150 agricultural drainage pump stations, most electrically powered.↩︎

  36. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  37. Gley soils: Hewitt (note 1). Gley soils form where the water table is at or near the surface for extended periods. The Hauraki Plains were extensively drained for dairy farming in the early-to-mid 20th century. Maintaining this drainage requires pumping stations — NZ has approximately 150 agricultural drainage pump stations, most electrically powered.↩︎

  38. Soil thermal properties are determined primarily by water content and bulk density. Wet soils (gley, organic) have high volumetric heat capacity (approximately 3.0–3.5 MJ/m³/°C) compared to dry, porous soils (pumice, allophanic: approximately 1.5–2.0 MJ/m³/°C). Under nuclear winter, reduced solar radiation input means these thermal differences translate into materially different spring warm-up rates. See Hillel, D. (2004), “Introduction to Environmental Soil Physics,” Academic Press, for soil thermal property fundamentals.↩︎

  39. Organic soils: Hewitt (note 1); also Pronger, J. et al. (2014), “Subsidence rates of drained agricultural peatlands in NZ and the relationship with time since drainage,” Journal of Environmental Quality, 43, 1442–1449. The Hauraki Plains have subsided by up to 3 metres since drainage began in the early 1900s. Subsidence rates are approximately 1–3 cm/yr on actively drained peat.↩︎

  40. Organic soils: Hewitt (note 1); also Pronger, J. et al. (2014), “Subsidence rates of drained agricultural peatlands in NZ and the relationship with time since drainage,” Journal of Environmental Quality, 43, 1442–1449. The Hauraki Plains have subsided by up to 3 metres since drainage began in the early 1900s. Subsidence rates are approximately 1–3 cm/yr on actively drained peat.↩︎

  41. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  42. Organic soils: Hewitt (note 1); also Pronger, J. et al. (2014), “Subsidence rates of drained agricultural peatlands in NZ and the relationship with time since drainage,” Journal of Environmental Quality, 43, 1442–1449. The Hauraki Plains have subsided by up to 3 metres since drainage began in the early 1900s. Subsidence rates are approximately 1–3 cm/yr on actively drained peat.↩︎

  43. Podzol soils: Hewitt (note 1). The West Coast receives 3,000–10,000 mm of rainfall annually, driving intense leaching that strips nutrients from upper soil horizons. Agricultural development on West Coast podzols has always been marginal and heavily dependent on fertiliser inputs.↩︎

  44. Podzol soils: Hewitt (note 1). The West Coast receives 3,000–10,000 mm of rainfall annually, driving intense leaching that strips nutrients from upper soil horizons. Agricultural development on West Coast podzols has always been marginal and heavily dependent on fertiliser inputs.↩︎

  45. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  46. Podzol soils: Hewitt (note 1). The West Coast receives 3,000–10,000 mm of rainfall annually, driving intense leaching that strips nutrients from upper soil horizons. Agricultural development on West Coast podzols has always been marginal and heavily dependent on fertiliser inputs.↩︎

  47. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  48. Lynn, I.H. et al. (2009), “Land Use Capability Survey Handbook,” 3rd edition, AgResearch, Hamilton, Landcare Research, Lincoln, and Institute of Geological and Nuclear Sciences, Lower Hutt. The LUC system classifies all NZ land into eight classes. Area figures are approximate, derived from the NZ Land Resource Inventory (NZLRI). Class I–III totals approximately 2.5 million hectares, though estimates vary depending on the edition and mapping resolution used. https://lris.scinfo.org.nz/↩︎

  49. Arable land conversion potential: Based on LUC classification data and existing land use data from Stats NZ Agricultural Production Statistics. The 700,000–1,000,000 hectare figure for convertible pastoral-to-cropping land is approximate and depends on excluding land with constraints (topography, drainage, soil depth) that make cropping impractical despite a favourable LUC class. See also Doc #75 for detailed regional conversion planning.↩︎

  50. Nuclear winter temperature and sunlight reduction estimates vary by model and scenario. The 3–5°C cooling range for the Southern Hemisphere is derived from Robock, A. et al. (2007), “Nuclear winter revisited with a modern climate model and current nuclear arsenals,” Journal of Geophysical Research, 112, D13107. Sunlight reduction of 10–30% reflects the range of soot injection scenarios. See also Doc #74 for NZ-specific modelling.↩︎

  51. Clark, R.G. et al. (1986), “Cobalt deficiency in NZ — a review of the biology and status,” NZ Journal of Agricultural Research, 29, 1–12. Also: Oldfield, J.E. (1999), “Selenium World Atlas,” Selenium-Tellurium Development Association. NZ is recognised as selenium-deficient across most of its agricultural land. Cobalt deficiency is concentrated in pumice soils of the central North Island but can occur on some other volcanic and highly leached soils.↩︎

  52. Hill Laboratories (Hamilton) and Eurofins (various NZ locations) are the primary commercial soil testing providers in NZ. Both operate standard analytical methods for agricultural soil testing (pH, Olsen P, Quick Test K, organic matter, and trace elements). Maintaining these laboratories as essential services requires reagent stocks, calibrated equipment, and trained technicians — all available domestically in the near term.↩︎

  53. Manaaki Whenua — Landcare Research maintains S-map (https://smap.landcareresearch.co.nz/) and the LRIS Portal (https://lris.scinfo.org.nz/). S-map coverage as of 2025 is approximately 45% of NZ at detailed scale. The New Zealand Land Resource Inventory (NZLRI) provides reconnaissance-level soil and land resource data for the entire country, mapped at 1:50,000 scale in the 1970s–1980s and subsequently updated.↩︎

  54. Manaaki Whenua — Landcare Research maintains S-map (https://smap.landcareresearch.co.nz/) and the LRIS Portal (https://lris.scinfo.org.nz/). S-map coverage as of 2025 is approximately 45% of NZ at detailed scale. The New Zealand Land Resource Inventory (NZLRI) provides reconnaissance-level soil and land resource data for the entire country, mapped at 1:50,000 scale in the 1970s–1980s and subsequently updated.↩︎

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