Soil pH — Benchmark Detail

Benchmark Value

No specific value — see range

Range: 6 to 7 pH

Thresholds: Lower: 5.5, Upper: 8

Optimal Range: 6 to 7

Direction: Higher is desirable ↑

Form: OptimalRange

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.

Evidence & Context

Reference value best available condition: pH 6.0 to 7.0 (water).3

Metric Definition:

Soil pH measured in 1:5 soil:water suspension

Benchmark Definition:

This benchmark represents the optimal topsoil pH range for productive, sustainably managed agricultural soils on volcanic-derived soils (Ferrosols) in the Tropical & Subtropical Maritime Islands biome. It reflects a managed ecological state achieved through liming and organic matter addition to overcome natural acidity.

Justification:

This reference range is directly grounded in Norfolk Island's measured best-practice agricultural soils and aligns with broader agronomic guidance. It represents a managed ecological state achieved through liming and organic matter building to overcome natural acidity.

Sources (3)

Preview of AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025,

AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025, Journal

Norfolk Island Agricultural Audit and Land Capability Assessment Report

View Source

Preview of Impacts of human activity on tropical soil quality in relation to future land productivity and biodiversity, May 2008 - Digital Commons @ USF - University of South Florida, accessed July 25, 2025,

Impacts of human activity on tropical soil quality in relation to future land productivity and biodiversity, May 2008 - Digital Commons @ USF - University of South Florida, accessed July 25, 2025,

Impacts of human activity on tropical soil quality in relation to future land productivity and biodiversity, May 2008 - Digital Commons @ USF - University of South Florida, accessed July 25, 2025,

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Preview of Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,

Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025, Government

Improving Soil Structure and pH Levels (DPIFM_NT) - Department of ..., accessed July 20, 2025

View Source

Supporting Sources (34)

Additional references from the underlying research that informed this benchmark.

(PDF) The pH of Australian soils: field results from a national survey - ResearchGate, accessed July 25, 2025,

Contextual Support Journal

Soil pH | Environment, land and water - Queensland Government, accessed August 28, 2025,

View Source

ACID SOILS OF THE TROPICS - ResearchGate, accessed July 25, 2025,

Contextual Support GreyLiterature

ACID SOILS OF THE TROPICS - ResearchGate, accessed July 25, 2025,

View Source

Anna Biesty - Restoring soil health and preventing flooding on the Norfolk coast, accessed July 25, 2025,

Contextual Support GreyLiterature

Anna Biesty - Restoring soil health and preventing flooding on the Norfolk coast, accessed July 25, 2025,

View Source

Australia – Sub-tropical – temperate - Earthdive, accessed July 25, 2025,

Contextual Support GreyLiterature

Australia – Sub-tropical – temperate - Earthdive, accessed August 1, 2025,

View Source

Australia state of the environment 2021: land, accessed May 11, 2025

Contextual Support Journal

Management Standards and Procedures for timber harvesting operations in Victoria’s State forests

View Source

Australia's bioregions (IBRA) - DCCEEW, accessed July 15, 2025

Contextual Support

Interim Biogeographic Regionalisation for Australia (IBRA), Version 7 (Regions), accessed July 12, 2025,

View Source

Preview of Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Contextual Support Journal

Root Structure and Functioning for Efficient Acquisition of Phosphorus: Matching Morphological and Physiological Traits

View Source

Christmas Island National Park - DCCEEW, accessed July 30, 2025,

Contextual Support Journal

Christmas Island National Park - DCCEEW, accessed August 2, 2025

View Source

Preview of Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,

Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,

Contextual Support Journal

Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations

View Source

Preview of How regenerative farming practices are revolutionising biodiversity in agriculture - Institute of Sustainability Studies, accessed July 25, 2025,

How regenerative farming practices are revolutionising biodiversity in agriculture - Institute of Sustainability Studies, accessed July 25, 2025,

Contextual Support GreyLiterature

Grazing support programs | Environment, land and water - Queensland Government, accessed July 28, 2025,

View Source

Land management in horticulture industries | Business Queensland, accessed July 25, 2025,

Contextual Support Government

Land management in horticulture industries | Business Queensland, accessed July 25, 2025,

View Source

Management and conservation of tropical acid soils for sustainable crop production, accessed July 25, 2025,

Contextual Support Journal

Management and conservation of tropical acid soils for sustainable crop production, accessed July 25, 2025,

View Source

Norfolk Island Food Supply, accessed July 25, 2025,

Contextual Support Journal

Norfolk Island Food Supply, accessed July 25, 2025,

View Source

Norfolk Island, accessed July 25, 2025,

Contextual Support Journal

Norfolk Island, accessed July 25, 2025,

View Source

PACIFIC ATOLL SOILS: CHEMISTRY, MINERALOGY AND CLASSIFICATION BY R. J. MORRISON - Smithsonian Institution, accessed July 25, 2025,

Direct Evidence Journal

PACIFIC ATOLL SOILS: CHEMISTRY, MINERALOGY AND CLASSIFICATION BY R. J. MORRISON - Smithsonian Institution, accessed July 25, 2025,

View Source

Preventing and managing erosion | Environment, land and water | Queensland Government, accessed July 20, 2025,

Contextual Support Government

Erosion & Sediment Control Guide for Building Sites - Clearwater, accessed July 20, 2025

View Source

Preview of Reducing Acidity of Tropical Acid Soil to Improve Phosphorus Availability and Zea mays L. Productivity through Efficient Use of Chicken Litter Biochar and Triple Superphosphate - MDPI, accessed July 25, 2025,

Reducing Acidity of Tropical Acid Soil to Improve Phosphorus Availability and Zea mays L. Productivity through Efficient Use of Chicken Litter Biochar and Triple Superphosphate - MDPI, accessed July 25, 2025,

Contextual Support Journal

View Source

Regenerative Agriculture - Norfolk FWAG, accessed July 25, 2025,

Contextual Support GreyLiterature

Regenerative Agriculture - Norfolk FWAG, accessed July 25, 2025,

View Source

Preview of Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 5, 2025,

Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 5, 2025,

Contextual Support Journal

Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 28, 2025,

View Source

Preview of Review of crop‐specific tolerance limits to acidity, salinity, and sodicity for seventeen cereal, pulse, and oilseed crops com - UQ eSpace - The University of Queensland, accessed July 25, 2025,

Review of crop‐specific tolerance limits to acidity, salinity, and sodicity for seventeen cereal, pulse, and oilseed crops com - UQ eSpace - The University of Queensland, accessed July 25, 2025,

Contextual Support Journal

Review of crop‐specific tolerance limits to acidity, salinity, and sodicity for seventeen cereal, pulse, and oilseed crops com - UQ eSpace - The University of Queensland, accessed July 25, 2025,

View Source

Soil Health & Your Wealth - presented by Graeme Sait - Regional Development Australia, accessed July 25, 2025,

Contextual Support GreyLiterature

Food System Mapping - Regional Development Australia - Mid North Coast NSW, accessed July 30, 2025,

View Source

Soil pH - Wikipedia, accessed July 25, 2025,

Contextual Support GreyLiterature

Soil pH - Wikipedia, accessed August 11, 2025,

View Source

Soil pH | Nutrient Management - Mosaic Crop Nutrition, accessed July 25, 2025,

Contextual Support GreyLiterature

Soil pH | Nutrient Management - Mosaic Crop Nutrition, accessed July 25, 2025,

View Source

Preview of Spatial variability in soil pH and land use as the main influential factor in the red beds of the Nanxiong Basin, China - PubMed Central, accessed July 25, 2025,

Spatial variability in soil pH and land use as the main influential factor in the red beds of the Nanxiong Basin, China - PubMed Central, accessed July 25, 2025,

Contextual Support Journal

Spatial variability in soil pH and land use as the main influential factor in the red beds of the Nanxiong Basin, China - PubMed Central, accessed July 25, 2025,

View Source

Success in the Face of Adversity – a Nutrition Farming® Testament, accessed July 25, 2025,

Contextual Support GreyLiterature

Success in the Face of Adversity – a Nutrition Farming® Testament, accessed July 25, 2025,

View Source

Surviving a Plague – Matt's Solution - Nutrition Matters, accessed July 25, 2025,

Contextual Support GreyLiterature

Surviving a Plague – Matt's Solution - Nutrition Matters, accessed July 25, 2025,

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Sustainability - Tropical Fruit World, accessed July 25, 2025,

Contextual Support GreyLiterature

Sustainability - Tropical Fruit World, accessed July 25, 2025,

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Sustainable Agriculture - Reef Catchments Sustainable Agriculture, accessed July 25, 2025,

Contextual Support Government

Sustainable Agriculture - Reef Catchments Sustainable Agriculture, accessed July 25, 2025,

View Source

The pH of Australian soils: field results from a national survey - CSIRO Publishing, accessed July 25, 2025,

Contextual Support Direct Evidence Journal

The pH of Australian soils: field results from a national survey - CSIRO Publishing, accessed August 28, 2025,

View Source

The Role of pH Adjustments in Queensland Soil Health - AHI Gardens, accessed July 25, 2025,

Contextual Support GreyLiterature

The Role of pH Adjustments in Queensland Soil Health - AHI Gardens, accessed July 25, 2025,

View Source

The Soil Health Principles of Regenerative Agriculture - Frantoio Grove, accessed July 25, 2025,

Contextual Support GreyLiterature

Managing Grazing to Restore Soil Health, Ecosystem Function, and Ecosystem Services - Frontiers, accessed July 28, 2025

View Source

Preview of The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies 1 | Request PDF - ResearchGate, accessed July 25, 2025,

The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies 1 | Request PDF - ResearchGate, accessed July 25, 2025,

Contextual Support Journal

The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies 1 | Request PDF - ResearchGate, accessed July 25, 2025,

View Source

Preview of The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies1 - ScholarSpace, accessed July 25, 2025,

The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies1 - ScholarSpace, accessed July 25, 2025,

Contextual Support Journal

The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies1 - ScholarSpace, accessed July 25, 2025,

View Source

What is Sustainable Agriculture? - Rainforest Alliance, accessed July 25, 2025,

Contextual Support GreyLiterature

What is Sustainable Agriculture? - Rainforest Alliance, accessed July 25, 2025,

View Source

Context

Region Australia
Biome Tropical & Subtropical Maritime Islands
Land Use Agricultural Crop Production
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 15 Mar 2026

Notes

Lower Critical Threshold: 5.5 pH. Upper Detrimental Threshold: 8 pH. The reference value represents the optimal topsoil pH range observed in productive, sustainably managed agricultural systems on volcanic-derived soils (Ferrosols) within the biome, as documented on Norfolk Island. This range (measured as 6.1-6.9) is the result of deliberate management (e.g., organic matter addition, appropriate liming) to ameliorate natural acidity, and thus represents a 'best available condition' for high ecological health and sustainable crop production. RangeFixup applied 2026-03-21 22:21 UTC: OptimalRangeHigh: 7.5 → 7; UpperBound: 7 → 7.5 [Migration] Original wider evidence range: 6 – 7.5 (retained OptimalRange: 6 – 7)

Related Benchmarks

Other benchmarks in the AUS-TMI-AGR-SPH family.