Soil pH — Benchmark Detail - Nature Index

Benchmark Value

5.5 pH

Direction: Higher is desirable ↑

Form: Point

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 19 benchmarks together — the OptimalRange form drives the primary score, while 18 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

The recommendation to maintain a topsoil $pH(CaCl_2)$ at a minimum of 5.5 is explicitly framed not merely for short-term productivity, but for long-term sustainability.

Metric Definition:

Soil pH measured in 0.01M calcium chloride solution ($pH(CaCl_2)$) representing potential acidity by displacing H+ ions from soil colloids.

Benchmark Definition:

This benchmark defines the minimum topsoil pH value for sustainable livestock grazing in Australia's tropical and subtropical rainforests, aimed at preventing long-term soil acidification and degradation.

Justification:

Derived from authoritative agricultural guidelines emphasizing long-term ecological resilience and prevention of subsoil acidification, a difficult-to-reverse degradation process.

Sources (1)

Preview of Procedure for Soil Respiration (CO2 Evolution from Rewetting a Dried Soil) - Soil Fertility, accessed July 9, 2025

Procedure for Soil Respiration (CO2 Evolution from Rewetting a Dried Soil) - Soil Fertility, accessed July 9, 2025 GreyLiterature

Tool 6.7 Soil health benchmarks and guidelines for managing ...

Supporting Sources (16)

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.

Preview of ASC - VERTOSOLS - Soil Science Australia

ASC - VERTOSOLS - Soil Science Australia

Contextual Support

What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase

Preview of Carbon storage in a Ferrosol under subtropical rainforest, tree plantations, and pasture is linked to soil aggregation - ResearchGate, accessed July 18, 2025,

Carbon storage in a Ferrosol under subtropical rainforest, tree plantations, and pasture is linked to soil aggregation - ResearchGate, accessed July 18, 2025,

Contextual Support Journal

Carbon storage in a Ferrosol under subtropical rainforest, tree plantations, and pasture is linked to soil aggregation - ResearchGate, accessed July 18, 2025,

Preview of Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - CSIRO Publishing, accessed August 5, 2025,

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - CSIRO Publishing, accessed August 5, 2025,

Contextual Support Journal

Ludwig, J.A., Bastin, G.N., Chewings, V.H., Eager, R.W., and Liedloff, A.C. (2005). Clearing savannas for use as rangelands in Queensland: Altered landscapes and water-erosion processes. Rangeland Journal, 27(2), 135-149.

Preview of Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - ResearchGate, accessed July 19, 2025,

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - ResearchGate, accessed July 19, 2025,

Contextual Support Journal

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - ResearchGate, accessed July 17, 2025

Preview of Healthy Soils for Sustainable Farms | FutureBeef

Healthy Soils for Sustainable Farms | FutureBeef

Contextual Support Journal

Healthy Soils for Sustainable Farms | FutureBeef, accessed August 4, 2025,

Preview of Manage soil acidity | EverGraze More livestock from perennials

Manage soil acidity | EverGraze More livestock from perennials

Contextual Support GreyLiterature

Manage soil acidity | EverGraze More livestock from perennials, accessed July 18, 2025,

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,

Preview of Soil health for vegetable production in Australia - Department of Primary Industries, Queensland, accessed July 18, 2025,

Soil health for vegetable production in Australia - Department of Primary Industries, Queensland, accessed July 18, 2025,

Contextual Support Journal

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 18, 2025,

Preview of Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,

Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,

Contextual Support Government

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 17, 2025

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

Preview of State Soils - Soil Science Australia, accessed July 18, 2025,

State Soils - Soil Science Australia, accessed July 18, 2025,

Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed July 20, 2025,

Preview of The impact of deforestation and pasture abandonment on soil properties in the wet tropics of Australia - ResearchGate, accessed July 18, 2025,

The impact of deforestation and pasture abandonment on soil properties in the wet tropics of Australia - ResearchGate, accessed July 18, 2025,

Contextual Support

Tool 6.7 Soil health benchmarks and guidelines for managing ..., accessed July 18, 2025,

Preview of Tropical Pasture - Barenbrug Australia, accessed July 18, 2025,

Tropical Pasture - Barenbrug Australia, accessed July 18, 2025,

Contextual Support Journal

P.PSH.1050 – Phosphorus management and requirements of tropical legume pasture swards - MLA, accessed July 18, 2025

Preview of V*. Clearing and burning brigalow (Acacia harpophylla) in Queensland, Australia, temporarily increases surface soil fertility prior to nutrient decline under cropping or grazing, accessed August 11, 2025,

V*. Clearing and burning brigalow (Acacia harpophylla) in Queensland, Australia, temporarily increases surface soil fertility prior to nutrient decline under cropping or grazing, accessed August 11, 2025,

Contextual Support Journal

V*. Clearing and burning brigalow (Acacia harpophylla) in Queensland, Australia, temporarily increases surface soil fertility prior to nutrient decline under cropping or grazing - CSIRO Publishing, accessed July 18, 2025,

Preview of www.barrierreef.org, accessed on May 25, 2025,

www.barrierreef.org, accessed on May 25, 2025,

Contextual Support Journal

Regenerative Agriculture Program restoring soil pH case study: Macdonald, Whites Flat/Koppio, accessed July 18, 2025,

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Livestock Grazing & Pasture
Assessment Not Stated
Evidence Type HealthyOperationalRange

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Lower Critical Threshold: 4.5 pH. The optimal pH range is 5.5 to 6.5, maximizing nutrient availability and supporting diverse pasture species. This benchmark supports long-term sustainability by preventing subsoil acidification. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.