Soil Phosphorus

AUS-TSR-FOR-SOP General High confidence

Benchmark Value

No specific value — see range
Range: 2 to 5 mg/kg
Thresholds: Lower: 2, Upper: 6
Optimal Range: 2 to 5
Direction: Higher 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 16 benchmarks together — the OptimalRange form drives the primary score, while 15 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Based on this synthesis, the proposed reference benchmark for available soil phosphorus (Colwell-P) is 2–5 mg/kg.

Metric Definition:

Available soil phosphorus measured by the Colwell-P method, representing the portion of soil P readily available for plant uptake during a growing season.

Benchmark Definition:

This benchmark represents the range of available soil phosphorus in tropical and subtropical rainforest production forestry soils that supports healthy native forests and sustainable productivity while avoiding detrimental ecological effects.

Justification:

The confidence is high due to strong convergence of evidence from independent studies including healthy native forests and rehabilitated sites showing impacts above 6 mg/kg.

Sources (2)

Preview of Soil phosphorus transformations along a 500,000-year coastal dune chronosequence under subtropical rainforest in Australia
Soil phosphorus transformations along a 500,000-year coastal dune chronosequence under subtropical rainforest in Australia Journal

Soil phosphorus transformations along a 500,000-year coastal dune chronosequence under subtropical rainforest in Australia

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Preview of Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value
Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value Journal

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

View Source

Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

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
Direct Evidence Journal

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

View Source

Context

  • Region Australia
  • Biome Tropical & Subtropical Rainforests
  • Land Use Production Forestry
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Superseded
  • Version 1
  • Effective From 24 Mar 2026
  • Effective To 26 Mar 2026

Notes

Lower Critical Threshold: 2 mg/kg. Upper Detrimental Threshold: 6 mg/kg. Levels above 6 mg/kg cause phosphorus toxicity, biodiversity loss, and eutrophication risk. Most critical for low P-buffering soils such as sandy Tenosols.

Related Benchmarks

Other benchmarks in the AUS-TSR-FOR-SOP family.

— mg/kg Moderate
Production Forestry · Pristine Reference
OptimalRange Active v2
2 mg/kg Moderate
Production Forestry · Pristine Reference
LowerThreshold Active v1
6 mg/kg High
Production Forestry · Pristine Reference
MinimumOnly Active v1