Soil pH

AUS-AMR-AGR-SPH General Moderate confidence

Benchmark Value

4.8 pH
Direction: Higher is desirable ↑
Form: MinimumOnly

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context. The scoring engine uses 8 benchmarks together — the OptimalRange form drives the primary score, while 7 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary OptimalRange Guard MinimumOnly Guard MaximumOnly Guard MinimumOnly Guard MaximumOnly Guard OptimalRange Guard OptimalRange Guard

Evidence & Context

There is strong scientific consensus that a topsoil pH (measured in 0.01 M calcium chloride, pHCaCl2​​) below 4.8 represents a critical threshold for most agricultural systems in Australia.

Metric Definition:

Topsoil pH measured in 0.01 M calcium chloride (pHCaCl2) indicating critical acidity threshold below which aluminum toxicity occurs.

Benchmark Definition:

Critical lower threshold for soil pH below which aluminum toxicity and ecosystem function collapse occur.

Justification:

Below this level, the concentration of soluble aluminum (Al3+) increases to toxic levels causing severe root stunting and compromised ecosystem resilience.

Sources (1)

Preview of Liming acidic soils creates profits, land use options but often more emissions - CSIRO Publishing
Liming acidic soils creates profits, land use options but often more emissions - CSIRO Publishing Journal

Liming acidic soils creates profits, land use options but often more emissions - CSIRO Publishing

View Source

Supporting Sources (19)

Additional references from the underlying research that informed this benchmark.

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

Caritat, P. de, & Cooper, M. (2011). The pH of Australian soils: Field results from a national survey. Soil Research, 49, 172-182.

View Source
Preview of Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 2, 2025,
Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 2, 2025,
Contextual Support Government

Northern and Yorke | Soil management - Landscape South Australia

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

How should we manage our soils to increase soil carbon?, accessed May 10, 2026

View Source
Preview of Balancing pasture development options for landscape diversity - CiteSeerX, accessed July 28, 2025
Balancing pasture development options for landscape diversity - CiteSeerX, accessed July 28, 2025
Contextual Support GreyLiterature

Balancing pasture development options for landscape diversity - CiteSeerX, accessed July 28, 2025

View Source
Preview of Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed July 16, 2025
Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed July 16, 2025
Contextual Support Journal

Soil Health: Supporting Rural Industries in the Wet Tropics, accessed August 28, 2025

View Source
Preview of Eyre Peninsula Farming Systems Summary 2021
Eyre Peninsula Farming Systems Summary 2021
Contextual Support Journal

Sodic & Alkaline Soil - Soil Quality Knowledge Base

View Source
Preview of Farming more sustainably by managing soil acidity, accessed July 28, 2025,
Farming more sustainably by managing soil acidity, accessed July 28, 2025,
Contextual Support Journal

Soil pH Explained - Soil Quality Knowledge Base, accessed July 28, 2025

View Source
Preview of Investigating the impacts of groundwater on soil properties and ..., accessed July 28, 2025
Investigating the impacts of groundwater on soil properties and ..., accessed July 28, 2025
Contextual Support Journal

Soil acidity and liming 4th edition - NSW Department of Primary Industries

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 July 20, 2025,

View Source
Preview of Soil Constraints in an Arid Environment—Challenges, Prospects, and Implications - MDPI, accessed July 6, 2025,
Soil Constraints in an Arid Environment—Challenges, Prospects, and Implications - MDPI, accessed July 6, 2025,
Contextual Support Journal

Soil Constraints in an Arid Environment—Challenges, Prospects, and Implications - MDPI

View Source
Preview of Soil pH - SA | Fact Sheets | soilquality.org.au
Soil pH - SA | Fact Sheets | soilquality.org.au
Contextual Support Government

Soil Acidity - NSW | Fact Sheets | soilquality.org.au

View Source
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,
Contextual Support Government

Australian dryland soils are acidic and nutrient‐depleted, and have unique microbial communities compared with other drylands - Arid Ecology Lab

View Source
Preview of Soil pH in northern and southern areas of the WA wheatbelt - DPIRD's Digital library, accessed July 28, 2025
Soil pH in northern and southern areas of the WA wheatbelt - DPIRD's Digital library, accessed July 28, 2025
Contextual Support Government

Soil pH in northern and southern areas of the WA wheatbelt - DPIRD's Digital library, accessed July 28, 2025

View Source
Preview of Soil Quality Knowledge Base. (n.d.). Soil pH.
Soil Quality Knowledge Base. (n.d.). Soil pH.
Contextual Support GreyLiterature

Soil Quality Knowledge Base. (n.d.). Soil pH.

View Source
Preview of The extent of surface soil acidity in the relatively intensive... | Download Table - ResearchGate, accessed July 28, 2025
The extent of surface soil acidity in the relatively intensive... | Download Table - ResearchGate, accessed July 28, 2025
Contextual Support

Agricultural production system in arid and semi-arid regions, accessed August 28, 2025

View Source
Preview of The pH of Australian soils: field results from a national survey - CSIRO Publishing, accessed July 25, 2025,
The pH of Australian soils: field results from a national survey - CSIRO Publishing, accessed July 25, 2025,
Contextual Support Journal

Soil pH Explained - Soil Quality Knowledge Base

View Source
Preview of Tool 6.7 Soil health benchmarks and guidelines for managing problem soils, accessed July 28, 2025
Tool 6.7 Soil health benchmarks and guidelines for managing problem soils, accessed July 28, 2025
Contextual Support Journal

LawrieCo2 Soil Carbon Regeneration System, accessed July 28, 2025

View Source
Preview of Transforming Agriculture in the Pilbara: Newman managed aquifer recharge (MAR) feasibility assessment - CSIRO Research Publications Repository, accessed July 28, 2025
Transforming Agriculture in the Pilbara: Newman managed aquifer recharge (MAR) feasibility assessment - CSIRO Research Publications Repository, accessed July 28, 2025
Contextual Support GreyLiterature

Transforming Agriculture in the Pilbara: Newman managed aquifer recharge (MAR) feasibility assessment - CSIRO Research Publications Repository, accessed July 28, 2025

View Source
Preview of Water repellent soils - CSIRO
Water repellent soils - CSIRO
Contextual Support Government

Water repellent soils - CSIRO

View Source

Context

  • Region Australia
  • Biome Arid Mountain Ranges & Uplands
  • Land Use Agricultural Crop Production
  • Assessment Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 9 Jun 2026

Notes

This threshold is particularly damaging in the subsurface and leads to impaired root systems and reduced microbial activity. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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

— pH Moderate
Agricultural Crop Production · Not Stated
OptimalRange Active v1
— pH Moderate
Agricultural Crop Production · Not Stated
OptimalRange Active v1
8.2 pH Moderate
Agricultural Crop Production · Not Stated
MaximumOnly Active v1