Soil Phosphorus

AUS-AIF-LVG-SOP General High confidence

Benchmark Value

15 mg/kg

Range: 8 to 20 mg/kg

Thresholds: Lower: 8, Upper: 20

Optimal Range: 8 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

A single value of 15 mg/kg Colwell P is proposed as the benchmark.

Metric Definition:

Colwell P concentration in the top 0-10 cm of soil, representing plant-available phosphorus.

Benchmark Definition:

The benchmark represents the transition from 'Moderate' to 'High' inherent fertility in natural floodplain soils, balancing productivity and conservation.

Justification:

This value is supported by a functional analysis defining an optimal ecological range of 8–20 mg/kg and the Queensland Government's Available-P map showing natural fertility classes.

Sources (1)

Preview of Queensland predicted soil bicarbonate-extractable phosphorus - map (Stage 3)

Queensland predicted soil bicarbonate-extractable phosphorus - map (Stage 3)

Supporting Sources (31)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Soil phosphorus—crop response calibration relationships and criteria for oilseeds, grain legumes and summer cereal crops grown in Australia - ResearchGate, accessed July 17, 2025,

(PDF) Soil phosphorus—crop response calibration relationships and criteria for oilseeds, grain legumes and summer cereal crops grown in Australia - ResearchGate, accessed July 17, 2025,

Contextual Support Journal

Interpretation of a single-point P buffering index for adjusting critical levels of the Colwell soil P test | Request PDF - ResearchGate, accessed July 17, 2025,

Preview of A simple phosphorus buffering index for Australian soils - University of Tasmania Open Access Repository Cover sheet

A simple phosphorus buffering index for Australian soils - University of Tasmania Open Access Repository Cover sheet

Contextual Support GreyLiterature

Cycling of phosphorus in grazing systems - NSW Department of Primary Industries

Preview of Are you on the map? Queensland phosphorus (P) map - MLA, accessed July 17, 2025,

Are you on the map? Queensland phosphorus (P) map - MLA, accessed July 17, 2025,

Direct Evidence Journal

Are you on the map? Queensland phosphorus (P) map - MLA, accessed July 17, 2025,

Preview of Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Contextual Support Journal

Root Structure and Functioning for Efficient Acquisition of Phosphorus: Matching Morphological and Physiological Traits

Preview of BASIC SOIL PROPERTIES - Land Resources and Environmental Sciences, accessed July 17, 2025,

BASIC SOIL PROPERTIES - Land Resources and Environmental Sciences, accessed July 17, 2025,

Contextual Support Journal

BASIC SOIL PROPERTIES - Land Resources and Environmental Sciences, accessed July 17, 2025,

Preview of Changes in soil carbon in response to flooding of the floodplain of a ..., accessed July 17, 2025

Changes in soil carbon in response to flooding of the floodplain of a ..., accessed July 17, 2025

Contextual Support Government

Floods - Bushland and agriculture - CSIRO, accessed July 17, 2025,

Preview of Channel Country Region Plant Index - FutureBeef, accessed July 17, 2025,

Channel Country Region Plant Index - FutureBeef, accessed July 17, 2025,

Contextual Support Journal

Channel Country Region Plant Index - FutureBeef, accessed July 17, 2025,

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,

Contextual Support Journal

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

Preview of Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed August 5, 2025,

Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed August 5, 2025,

Contextual Support GreyLiterature

The relationships between land management practices and soil condition and the quality of ecosystem services delivered from agri - DAFF

Preview of Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed July 17, 2025,

Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed July 17, 2025,

Contextual Support Journal

Discover the Top 6 Benefits of Regenerative Farming in Australia, accessed July 17, 2025,

Preview of Efficiency of soil and fertilizer phosphorus use - Food and Agriculture Organization of the United Nations, accessed July 17, 2025,

Efficiency of soil and fertilizer phosphorus use - Food and Agriculture Organization of the United Nations, accessed July 17, 2025,

Contextual Support Government

Total Phosphorus - DCCEEW, accessed July 17, 2025,

Preview of How Biodiversity-Friendly Is Regenerative Grazing? - Frontiers, accessed July 17, 2025,

How Biodiversity-Friendly Is Regenerative Grazing? - Frontiers, accessed July 17, 2025,

Contextual Support Journal

Loss of phosphorus and nitrogen in runoff and subsurface drainage from high and low input pastures grazed by sheep in southern Australia - CSIRO PUBLISHING | Soil Research, accessed July 17, 2025,

Preview of Improved maps of available phosphorus for the state of Queensland ..., accessed July 17, 2025,

Improved maps of available phosphorus for the state of Queensland ..., accessed July 17, 2025,

Direct Evidence Journal

Updating the Phosphorus Map of Queensland - FutureBeef, accessed July 18, 2025,

Preview of Indicative Soil Phosphorus Report | LongPaddock | Queensland Government

Indicative Soil Phosphorus Report | LongPaddock | Queensland Government

Direct Evidence Government

Indicative Soil Phosphorus Report | LongPaddock | Queensland Government, accessed August 1, 2025

Preview of Lake Eyre Basin Rivers Assessment Implementation Plan Project - ResearchGate, accessed July 22, 2025,

Lake Eyre Basin Rivers Assessment Implementation Plan Project - ResearchGate, accessed July 22, 2025,

Contextual Support

Cycling of phosphorus in grazing systems - NSW Department of Primary Industries, accessed July 17, 2025,

Preview of Managing soils - Department of Primary Industries and Regional Development, accessed July 21, 2025,

Managing soils - Department of Primary Industries and Regional Development, accessed July 21, 2025,

Contextual Support Journal

Gilgai wetlands - WetlandInfo, accessed July 19, 2025,

Preview of P dynamics in vertosols – which soil properties affect declines in P availability over time? Are there differences between MAP, accessed July 17, 2025,

P dynamics in vertosols – which soil properties affect declines in P availability over time? Are there differences between MAP, accessed July 17, 2025,

Contextual Support GreyLiterature

P dynamics in vertosols – which soil properties affect declines in P availability over time? Are there differences between MAP, accessed July 17, 2025,

Preview of Phosphorus Buffering Index (0 - 10 cm) | South Australia | Examine | soilquality.org.au, accessed July 17, 2025,

Phosphorus Buffering Index (0 - 10 cm) | South Australia | Examine | soilquality.org.au, accessed July 17, 2025,

Contextual Support Government

Phosphorus Buffering Index (0 - 10 cm) | South Australia | Examine | soilquality.org.au, accessed July 17, 2025,

Preview of Phosphorus dynamics in Vertosols: improving fertilizer management - Agronomy Australia Proceedings, accessed July 17, 2025,

Phosphorus dynamics in Vertosols: improving fertilizer management - Agronomy Australia Proceedings, accessed July 17, 2025,

Contextual Support Journal

Phosphorus dynamics in Vertosols: improving fertilizer management - Agronomy Australia Proceedings, accessed July 17, 2025,

Preview of Phosphorus management of beef cattle in northern Australia - MLA, accessed July 17, 2025,

Phosphorus management of beef cattle in northern Australia - MLA, accessed July 17, 2025,

Contextual Support Government

Phosphorus management of beef cattle in northern Australia - MLA, accessed July 17, 2025,

Preview of Phosphorus requirements of Australian native plants - ResearchGate, accessed August 4, 2025

Phosphorus requirements of Australian native plants - ResearchGate, accessed August 4, 2025

Contextual Support Journal

The Big Phosphorus Issue - Australian Native Plants — The Gardeners Lodge, accessed August 1, 2025

Preview of phosphorus-fact.pdf - Soil Wealth, accessed July 22, 2025,

phosphorus-fact.pdf - Soil Wealth, accessed July 22, 2025,

Contextual Support Journal

Field benchmarking of the critical external phosphorus requirements of pasture legumes for southern Australia - CSIRO Publishing, accessed July 17, 2025,

Preview of Queensland predicted soil bicarbonate-extractable phosphorus - map (Stage 3), accessed July 17, 2025,

Queensland predicted soil bicarbonate-extractable phosphorus - map (Stage 3), accessed July 17, 2025,

Contextual Support Government

Queensland predicted soil bicarbonate-extractable phosphorus - map (Stage 3), accessed July 17, 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 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 testing for phosphorus: comparing the Mehlich 3 and Colwell procedures for soils of south-western Australia | Request PDF - ResearchGate, accessed July 17, 2025,

Soil testing for phosphorus: comparing the Mehlich 3 and Colwell procedures for soils of south-western Australia | Request PDF - ResearchGate, accessed July 17, 2025,

Methodology Source Journal

Soil testing for phosphorus: comparing the Mehlich 3 and Colwell procedures for soils of south-western Australia | Request PDF - ResearchGate, accessed July 17, 2025,

Preview of The Ecological and Hydrological Significance of Ephemeral and Intermittent Streams in the Arid and Semi-arid American Southwest - Environmental Protection Agency (EPA)

The Ecological and Hydrological Significance of Ephemeral and Intermittent Streams in the Arid and Semi-arid American Southwest - Environmental Protection Agency (EPA)

Contextual Support Journal

The Phosphorus Buffering Index – What Does it Mean for Your Soil? - Summit Fertilizers, accessed July 17, 2025,

Preview of The Ecological and Hydrological Significance of Ephemeral and Intermittent Streams in the Arid and Semi-arid American Southwest - Environmental Protection Agency (EPA), accessed July 17, 2025,

The Ecological and Hydrological Significance of Ephemeral and Intermittent Streams in the Arid and Semi-arid American Southwest - Environmental Protection Agency (EPA), accessed July 17, 2025,

Contextual Support Journal

The Ecological and Hydrological Significance of Ephemeral and Intermittent Streams in the Arid and Semi-arid American Southwest - Environmental Protection Agency (EPA), accessed July 17, 2025,

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

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

Contextual Support Government

Understanding soil tests for pastures

Preview of What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase, accessed July 17, 2025,

What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase, accessed July 17, 2025,

Contextual Support GreyLiterature

What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase, accessed July 17, 2025,

Preview of www.barrierreef.org, accessed on May 25, 2025,

www.barrierreef.org, accessed on May 25, 2025,

Direct Evidence Journal

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

Context

Region Australia
Biome Arid Inland Floodplains & Ephemeral River Systems
Land Use Livestock Grazing & Pasture
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Lower Critical Threshold: 8 mg/kg. Upper Detrimental Threshold: 20 mg/kg. The lower critical threshold is >8 mg/kg, below which P is inadequate for sustainable livestock production. The upper detrimental threshold is >20 mg/kg, above which native perennial grasses are displaced by introduced species, indicating ecological degradation. This benchmark is most applicable to cracking clay soils (Vertosols) with moderate-to-high Phosphorus Buffering Index (PBI).