Soil Phosphorus

AUS-TGP-CON-SOP General High confidence

Benchmark Value

20 mg/kg
Thresholds: Lower: —, Upper: 20
Direction: Lower is desirable ↓
Form: MaximumOnly

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

Evidence & Context

A value of approximately 20 mg/kg Colwell-P should be considered the upper limit for maintaining a native-dominated grassy sward.

Metric Definition:

Available phosphorus (Colwell-P) concentration in soil indicating onset of ecological degradation.

Benchmark Definition:

Upper detrimental threshold of soil available phosphorus beyond which native biodiversity declines in temperate grassy woodlands under conservation management.

Justification:

Based on multiple sources showing native species decline and exotic species dominance above this level.

Sources (1)

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, GreyLiterature

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 17, 2025,

View Source

Supporting Sources (18)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Phosphorus accumulation and other changes in soil ..., accessed August 11, 2025
(PDF) Phosphorus accumulation and other changes in soil ..., accessed August 11, 2025
Contextual Support Journal

(PDF) Phosphorus accumulation and other changes in soil ..., accessed August 11, 2025

View Source
Preview of A new detailed map of total phosphorus stocks in Australian soil - ResearchGate, accessed August 11, 2025
A new detailed map of total phosphorus stocks in Australian soil - ResearchGate, accessed August 11, 2025
Contextual Support Journal

A new detailed map of total phosphorus stocks in Australian soil

View Source
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

View Source
Preview of Australian Journal of Botany - CSIRO PUBLISHING, accessed August 11, 2025
Australian Journal of Botany - CSIRO PUBLISHING, accessed August 11, 2025
Contextual Support Journal

The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition - CSIRO Publishing, accessed August 5, 2025,

View Source
Preview of Busted: The I-hate-phosphorus myth - AusBonsai, accessed August 11, 2025
Busted: The I-hate-phosphorus myth - AusBonsai, accessed August 11, 2025
Contextual Support GreyLiterature

Busted: The I-hate-phosphorus myth - AusBonsai, accessed August 11, 2025

View Source
Preview of Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Contextual Support Direct Evidence Journal

(PDF) Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 4, 2025,

View Source
Preview of Old field restoration improves biodiversity and soils and large parts of Australia have huge potential to be remediated, accessed August 11, 2025
Old field restoration improves biodiversity and soils and large parts of Australia have huge potential to be remediated, accessed August 11, 2025
Contextual Support GreyLiterature

Old field restoration improves biodiversity and soils and large parts of Australia have huge potential to be remediated, accessed August 11, 2025

View Source
Preview of Phosphorus - WA | Fact Sheets | soilquality.org.au, accessed August 4, 2025
Phosphorus - WA | Fact Sheets | soilquality.org.au, accessed August 4, 2025
Contextual Support GreyLiterature

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

View Source
Preview of Phosphorus fertiliser management for pastures ... - CSIRO Publishing, accessed August 11, 2025
Phosphorus fertiliser management for pastures ... - CSIRO Publishing, accessed August 11, 2025
Contextual Support Methodology Source Journal

Phosphorus fertiliser management for pastures ... - CSIRO Publishing

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
Preview of Phosphorus: a finite resource essential for life, critical for agriculture and food security - CSIRO, accessed August 11, 2025
Phosphorus: a finite resource essential for life, critical for agriculture and food security - CSIRO, accessed August 11, 2025
Contextual Support Government

Nitrogen and Phosphorus Retranslocation of Leaves and Stemwood in a Mature Eucalyptus Forest Exposed to 5 Years of Elevated CO2 - Frontiers, accessed July 19, 2025,

View Source
Preview of Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns - the UWA Profiles and Research Repository, accessed August 11, 2025
Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns - the UWA Profiles and Research Repository, accessed August 11, 2025
Contextual Support Direct Evidence Journal

Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns - the UWA Profiles and Research Repository, accessed August 11, 2025

View Source
Preview of Sensitivity of seedling growth to phosphorus supply in six tree species of the Australian Great Western Woodlands - ResearchGate, accessed August 11, 2025
Sensitivity of seedling growth to phosphorus supply in six tree species of the Australian Great Western Woodlands - ResearchGate, accessed August 11, 2025
Contextual Support Journal

Understanding soil tests for pastures | Soil | Farm management ..., accessed May 15, 2025,

View Source
Preview of Soil phosphorus and tree cover modify the effects of livestock grazing on plant species richness in Australian grassy woodland - ResearchGate, accessed August 11, 2025
Soil phosphorus and tree cover modify the effects of livestock grazing on plant species richness in Australian grassy woodland - ResearchGate, accessed August 11, 2025
Direct Evidence

(PDF) Soil phosphorus and tree cover modify the effects of livestock grazing on plant species richness in Australian grassy woodland - ResearchGate

View Source
Preview of The changing the availability of nutrients in global grasslands | TERN Australia, accessed August 11, 2025
The changing the availability of nutrients in global grasslands | TERN Australia, accessed August 11, 2025
Contextual Support Government

The changing the availability of nutrients in global grasslands ..., accessed August 28, 2025,

View Source
Preview of The development and application of functions describing pasture yield responses to phosphorus, potassium and sulfur in Australia using meta-data analysis and derived soil-test calibration relationships - CSIRO Publishing, accessed August 11, 2025
The development and application of functions describing pasture yield responses to phosphorus, potassium and sulfur in Australia using meta-data analysis and derived soil-test calibration relationships - CSIRO Publishing, accessed August 11, 2025
Contextual Support Methodology Source Journal

The role of regenerative agriculture in sustainable land use - ClimateWorks Australia

View Source
Preview of Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value - Australian Centre for Geomechanics, accessed August 11, 2025
Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value - Australian Centre for Geomechanics, accessed August 11, 2025
Contextual Support Journal

Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value - Australian Centre for Geomechanics

View Source
Preview of Why phosphorus is important - NSW Department of Primary Industries, accessed August 4, 2025
Why phosphorus is important - NSW Department of Primary Industries, accessed August 4, 2025
Contextual Support Government

(PDF) Individual plant species responses to phosphorus and ...

View Source

Context

  • Region Australia
  • Biome Temperate Grassy Woodlands & Plains
  • Land Use Conservation / Protected Natural Areas
  • Assessment Conservation Target
  • Vegetation Woodland
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 15 Mar 2026

Notes

This threshold is the most important management boundary for soil phosphorus in conservation.

Related Benchmarks

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

— mg/kg High
Conservation / Protected Natural Areas · Pristine Reference · Woodland
OptimalRange Active v1
— mg/kg High
Conservation / Protected Natural Areas · Conservation Target · Woodland
OptimalRange Active v1
— mg/kg High
Conservation / Protected Natural Areas · Conservation Target
OptimalRange Superseded v1