Soil pH — Benchmark Detail - Nature Index

Benchmark Value

4.5 pH

Thresholds: Lower: 4.5, Upper: —

Direction: Lower is desirable ↓

Form: LowerThreshold

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 3 benchmarks together — the OptimalRange form drives the primary score, while 2 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard LowerThreshold Guard

Evidence & Context

Based on this evidence, a $pH(CaCl_2)$ of 4.5 is identified as the lower critical threshold.

Metric Definition:

Soil pH measured in 0.01M calcium chloride solution (pH(CaCl2)) representing the lower critical threshold for ecological integrity.

Benchmark Definition:

The lower critical threshold below which ecological function and pasture productivity are significantly constrained.

Justification:

At pH below 4.5, aluminum toxicity and cascading ecosystem failures become prevalent, impairing microbial function and pasture health.

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

Soil pH and Organic Matter - MSU Extension | Montana State University, accessed July 28, 2025,

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

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

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

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 August 28, 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

Healthy soils and water infiltration in the paddock - Local Land ...

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 GreyLiterature

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

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

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

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

Contextual Support Journal

Relationship between the Floristic Composition and Soil Characteristics of a Tropical Rainforest (TRF) - MDPI, accessed July 18, 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

Soils of the Koolpinyah Surface (Chen et al., 2005)

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

Potassium for high-performing pastures | Nutrient Advantage, accessed July 28, 2025,

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Livestock Grazing & Pasture
Assessment Conservation Target
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Represents a state of significant ecological compromise with high risk of soil erosion and loss of sensitive legumes.

Related Benchmarks

Other benchmarks in the AUS-TSR-LVG-SPH family.