Soil pH

Benchmark Value

4 pH

Thresholds: Lower: 4, Upper: —

Direction: Higher 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 2 benchmarks together — the LowerThreshold form drives the primary score, while 1 guard(s) constrain the result.

Contributing Benchmarks

LowerThreshold Primary UpperThreshold Guard

Evidence & Context

Lower Critical Threshold is pH < 4.0.

Metric Definition:

Lower critical pH threshold indicating catastrophic ecosystem degradation from Acid Sulfate Soil activation.

Benchmark Definition:

Critical pH below which Acid Sulfate Soil activation causes ecosystem collapse.

Justification:

Based on documented catastrophic acidification events and toxic metal mobilization.

Sources (1)

Preview of National Guidance on Acid Sulfate Soils - Water Quality Australia

National Guidance on Acid Sulfate Soils - Water Quality Australia Journal

Managing soils - Department of Primary Industries and Regional Development

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Supporting Sources (9)

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,

Direct Evidence Journal

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

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ASC - VERTOSOLS - Soil Science Australia

Contextual Support

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

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Australian Soil Classification edition 3 - CALCAROSOLS

Contextual Support Government

Soil Characteristics and Management Options | VRO - Victorian Resources Online

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Ecological impacts of flood mitigation and drainage in coastal lowlands - AustLII

Contextual Support

Ecological impacts of flood mitigation and drainage in coastal lowlands - AustLII

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Soil Constraints in an Arid Environment - Encyclopedia.pub

Contextual Support GreyLiterature

Soil Constraints in an Arid Environment - Encyclopedia.pub, accessed July 27, 2025,

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Soil pH - SA | Fact Sheets | soilquality.org.au

Contextual Support Government

Soil pH - SA | Fact Sheets | soilquality.org.au, accessed July 30, 2025,

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Victorian Resources Online | Resources | Support and resources ...

Contextual Support Government

Structural controls on the orientation of erosion gullies in mid-western New South Wales, Australia, accessed July 22, 2025

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Water and sediment quality in the Diamantina-Georgina River ..., accessed July 21, 2025,

Contextual Support Journal

Water and sediment quality in the Diamantina-Georgina River ..., accessed July 21, 2025,

View Source

Water and sediment quality in the Diamantina-Georgina River catchment, Lake Eyre Basin

Direct Evidence Journal

Water quality in the Georgina-Diamantina River catchment

View Source

Benchmark Value

Scoring Curve

Contributing Benchmarks

Evidence & Context

Sources (1)

Supporting Sources (9)

Context

Lifecycle

Notes

Related Benchmarks