Soil Phosphorus

AUS-TMI-CON-SOP General Moderate confidence

Benchmark Value

No specific value — see range

Range: 2 to 15 mg/kg

Optimal Range: 2 to 15

Direction: Lower is desirable ↓

Form: OptimalRange

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 11 benchmarks together — the OptimalRange form drives the primary score, while 10 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

The optimal condition is therefore defined by a low level of available phosphorus, likely in the range of <2 to 15 mg/kg (Colwell P).

Metric Definition:

Available phosphorus (Colwell P) concentration in soil, measured by the Colwell P test, representing the plant-available phosphorus fraction relevant for ecological health assessment.

Benchmark Definition:

This benchmark represents the optimal ecological range of available phosphorus in soil that supports high endemic biodiversity and ecosystem resilience in phosphorus-sensitive tropical and subtropical maritime island conservation areas.

Justification:

This range reflects the naturally low-phosphorus state that maximizes endemic biodiversity and ecosystem resilience in phosphorus-sensitive island ecosystems.

Sources (1)

Preview of Common soil types | Environment, land and water | Queensland ...

Common soil types | Environment, land and water | Queensland ... Government

Phosphorus nutrition of phosphorus-sensitive Australian native ...

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Supporting Sources (6)

Additional references from the underlying research that informed this benchmark.

A simple phosphorus buffering index for Australian soils - ResearchGate

Contextual Support GreyLiterature

(PDF) A simple phosphorus buffering index for Australian soils - ResearchGate

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Preview of Critical phosphorus values from the Better Fertiliser Decisions for Pastures project: early insights from validation trials - BioOne Complete, accessed July 28, 2025,

Critical phosphorus values from the Better Fertiliser Decisions for Pastures project: early insights from validation trials - BioOne Complete, accessed July 28, 2025,

Direct Evidence Journal

Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA

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LORD HOWE ISLAND BOARD On-Site Wastewater Management ...

Contextual Support Journal

LORD HOWE ISLAND BOARD On-Site Wastewater Management ...

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Preview of Phosphorus nutrition of phosphorus-sensitive Australian native plants: threats to plant communities in a global biodiversity hotspot - PMC

Phosphorus nutrition of phosphorus-sensitive Australian native plants: threats to plant communities in a global biodiversity hotspot - PMC

Contextual Support Journal

(PDF) Sensitivity of seedling growth to phosphorus supply in six tree ...

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Soil and Landscape Grid National Soil Attribute Maps - Total Phosphorus (3" resolution) - Release 2 - CSIRO Data Access Portal

Direct Evidence Government

Soil and Landscape Grid National Soil Attribute Maps - Total Phosphorus (3" resolution) - Release 2

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Torres Strait Islands - Wikipedia, accessed July 27, 2025,

Contextual Support GreyLiterature

Torres Strait Islands - Wikipedia, accessed August 4, 2025,

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Context

Region Australia
Biome Tropical & Subtropical Maritime Islands
Land Use Conservation / Protected Natural Areas
Assessment Conservation Target
Evidence Type HealthyOperationalRange

Lifecycle

Status Active
Version 1
Effective From 9 Jun 2026

Notes

The range is indicative and should be applied with caution, considering local soil phosphorus sorption characteristics and data limitations. No upper detrimental threshold — higher values are always worse beyond this range.

Related Benchmarks

Other benchmarks in the AUS-TMI-CON-SOP family.