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 due to Acid Sulfate Soil activation.

Benchmark Definition:

pH level below which acid sulfate soil activation causes catastrophic acidification and ecosystem collapse.

Justification:

Based on documented cases of acid sulfate soil oxidation leading to pH drops below 4.0 and severe ecological harm.

Sources (2)

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

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

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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 (8)

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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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

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Benchmark Value

Scoring Curve

Contributing Benchmarks

Evidence & Context

Sources (2)

Supporting Sources (8)

Context

Lifecycle

Notes

Related Benchmarks