Soil Phosphorus

AUS-AMR-LVG-SOP General Moderate confidence

Benchmark Value

15 mg/kg

Range: 20 to 20 mg/kg

Thresholds: Lower: —, Upper: 26

Optimal Range: 20 to 20

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 8 benchmarks together — the OptimalRange form drives the primary score, while 7 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary LowerThreshold Guard UpperThreshold Guard Point Guard OptimalRange Guard LowerThreshold Guard UpperThreshold Guard Point Guard

Evidence & Context

Therefore, a benchmark value of 15 mg/kg (Colwell P) is proposed.

Metric Definition:

Colwell P concentration in soil representing the best available ecological condition for native pastures under sustainable grazing.

Benchmark Definition:

This benchmark represents an optimal ecological state for well-managed native pastures in Australia's arid and semi-arid zones, balancing productivity and ecological stability.

Justification:

It is derived by synthesizing findings that identify an upper detrimental threshold with targets for healthy native grass systems. The selected benchmark of 15 mg/kg sits at the conservative, safe lower end of this productive range, providing a buffer against the detrimental threshold.

Sources (3)

Preview of (PDF) Mineral Nutrition of Plants in Australia's Arid Zone - ResearchGate, accessed July 23, 2025,

(PDF) Mineral Nutrition of Plants in Australia's Arid Zone - ResearchGate, accessed July 23, 2025, Journal

Ecology of Australia: The effects of nutrient-poor soils and intense fires - ResearchGate

View Source

Phosphorus fertiliser management for pastures ... - CSIRO Publishing, accessed August 11, 2025 Journal

Phosphorus fertiliser management for pastures ... - CSIRO Publishing

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Soil nutrient critical limits | MBFP | More Beef from Pastures Journal

Soil nutrient critical limits | MBFP | More Beef from Pastures

View Source

Supporting Sources (28)

Additional references from the underlying research that informed this benchmark.

(PDF) Mineral Nutrition of Plants in Australia's Arid Zone - ResearchGate, accessed July 13, 2025

Contextual Support

(PDF) Mineral Nutrition of Plants in Australia's Arid Zone - ResearchGate

View Source

Agricultural Phosphorus and Eutrophication - Second Edition - USDA ARS

Contextual Support Journal

Agricultural Phosphorus and Eutrophication - Second Edition - USDA ARS

View Source

Australian Soil Classification edition 3 - CALCAROSOLS, accessed July 26, 2025

Contextual Support

ASC - RUDOSOLS - Soil Science Australia

View Source

Australian Soil: Definition, Classification, Types and Quality - Access EP, accessed July 30, 2025

Contextual Support GreyLiterature

Australian Soil: Definition, Classification, Types and Quality - Access EP

View Source

Common soil types | Environment, land and water - Queensland Government, accessed August 9, 2025

Contextual Support Government

Australian Soil Classification edition 3 - CALCAROSOLS

View Source

Crop NutritioN FACT SHEET - Grains Research and Development Corporation (GRDC)

Contextual Support Journal

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

View Source

Ecology of Australia: the effects of nutrient-poor soils and intense fires - PubMed, accessed August 11, 2025,

Contextual Support Journal

Ecology of Australia: the effects of nutrient-poor soils and intense fires - PubMed

View Source

Fertilisers and the environment - NSW Department of Primary Industries

Contextual Support Journal

Fertilisers and the environment - NSW Department of Primary Industries

View Source

Fertilisers and the environment, accessed August 4, 2025

Contextual Support Government

(PDF) Soil phosphorus–crop response calibration relationships and ...

View Source

Field benchmarking of the critical external phosphorus requirements of pasture legumes for southern Australia - ResearchGate

Direct Evidence Journal

Field benchmarking of the critical external phosphorus requirements of pasture legumes for southern Australia - ResearchGate

View Source

Find out the Different Types of Soil in Australia - Kelly Tillage AUS, accessed July 6, 2025,

Contextual Support GreyLiterature

ASC - TENOSOLS - Soil Science Australia

View Source

How to reduce Fertiliser Costs - Eco-logical Solutions - Learning from Nature

Contextual Support GreyLiterature

Restoration of degraded grazing country in the semi-arid areas of NSW

View Source

Phosphorus - WA | Fact Sheets | soilquality.org.au, accessed August 4, 2025

Contextual Support GreyLiterature

Phosphorus - Tas | Fact Sheets | soilquality.org.au

View Source

Phosphorus Buffering Capacity Indices as Related to Soil Properties and Plant Uptake

Contextual Support GreyLiterature

Phosphorus Buffering Capacity Indices as Related to Soil Properties and Plant Uptake

View Source

Preview of Phosphorus Nutrition of Proteaceae in Severely Phosphorus-Impoverished Soils: Are There Lessons To Be Learned for Future Crops? - PubMed Central, accessed August 4, 2025

Phosphorus Nutrition of Proteaceae in Severely Phosphorus-Impoverished Soils: Are There Lessons To Be Learned for Future Crops? - PubMed Central, accessed August 4, 2025

Contextual Support Journal

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

View Source

Plant mechanisms to optimise access to soil phosphorus - ResearchGate

Contextual Support Journal

Plant mechanisms to optimise access to soil phosphorus - ResearchGate

View Source

Regenerative Grazing workshop proves popular despite the dust - Landscape SA

Contextual Support Government

Regenerative Grazing workshop proves popular despite the dust - Landscape SA

View Source

Regenerative Grazing: 3 Different Approaches - Shorthandstories.com, accessed August 5, 2025,

Contextual Support GreyLiterature

Regenerative Grazing: 3 Different Approaches - Shorthandstories.com

View Source

Restoration of degraded grazing country in the semi-arid areas of ..., accessed July 10, 2025,

Contextual Support Journal

Pasture and grazing land: assessment of sustainability using invertebrate bioindicators

View Source

Soil condition | NSW State of the Environment, accessed August 10, 2025,

Contextual Support Government

The relationships between land management practices and soil condition and the quality of ecosystem services delivered from agri - DAFF, accessed July 28, 2025,

View Source

Soil phosphorus-crop response calibration relationships and criteria for winter cereal crops grown in Australia

Contextual Support

RCS Regenerative Grazing Principles - Resource Consulting Services

View Source

Soil phosphorus–crop response calibration ... - CSIRO Publishing, accessed May 11, 2025,

Contextual Support Journal

Soil phosphorus–crop response calibration relationships and criteria for winter cereal crops grown in Australia - CSIRO Publishing

View Source

Preview of The development and application of functions describing pasture yield responses to phosphorus, potassium and sulfur in Australia - DPIRD's Digital library

The development and application of functions describing pasture yield responses to phosphorus, potassium and sulfur in Australia - DPIRD's Digital library

Contextual Support

The development and application of functions describing pasture yield responses to phosphorus, potassium and sulfur in Australia - DPIRD's Digital library

View Source

theaustralianalpsnationalparks.org, accessed on May 25, 2025,

Contextual Support Journal

theaustralianalpsnationalparks.org

View Source

Understanding Soil Phosphorus - Integrated Pest and Crop Management

Contextual Support Journal

Understanding Soil Phosphorus - Integrated Pest and Crop Management

View Source

Understanding soil tests for pastures | Soil | Farm management ...

Contextual Support Government

Understanding soil tests for pastures | Soil | Farm management ...

View Source

Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025

Contextual Support Government

Understanding soil tests for pastures

View Source

What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase, accessed August 5, 2025,

Contextual Support Government

Scanlan, C. A., et al. (2013). Soil Quality: 10 Plant Nutrition. CCMA Soil Health Knowledge Base.

View Source

Context

Region Australia
Biome Arid Mountain Ranges & Uplands
Land Use Livestock Grazing & Pasture
Assessment Pristine Reference
Evidence Type TargetCondition

Lifecycle

Status Active
Version 1
Effective From 25 Mar 2026

Notes

Upper Detrimental Threshold: Research demonstrates that retaining desirable native perennial grasses becomes difficult once Colwell P exceeds 20 mg/kg, as they are outcompeted by annuals and legumes, triggering an ecological regime shift towards a less stable state. Optimal Range: For productive, fertility-tolerant native pastures (e.g., Microlaena dominant), an optimal range of 10-13 mg/kg Olsen P is recommended. Converting to Colwell P (approx. factor of 2 for loamy soils) gives a target range of ~20-26 mg/kg. Lower Critical Threshold: The primary function of a lower boundary in this context is to ensure sufficient plant vigour to maintain minimum groundcover (~40%) for erosion control, likely met at Colwell P levels of ~10-12 mg/kg.