Soil Phosphorus

AUS-TSR-FOR-SOP General High confidence

Benchmark Value

6 mg/kg
Thresholds: Lower: —, Upper: 6
Direction: Lower is desirable ↓
Form: MinimumOnly

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

Upper Detrimental Threshold: >6 mg/kg. Levels above this are demonstrably harmful, causing P-toxicity in native flora, loss of biodiversity, and increased risk of waterway eutrophication.

Metric Definition:

Available soil phosphorus measured by the Colwell-P method indicating the maximum safe level to avoid ecological harm.

Benchmark Definition:

This benchmark defines the upper phosphorus concentration limit in tropical and subtropical rainforest production forestry soils above which ecological harm occurs.

Justification:

Based on evidence from rehabilitated sites showing negative impacts on native plant communities at levels above 6 mg/kg.

Sources (1)

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 (2)

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
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
Direct Evidence Journal

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

View Source

Context

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

Lifecycle

  • Status Active
  • Version 1
  • Effective From 24 Mar 2026

Notes

This is a hard ecological boundary to prevent biodiversity loss and eutrophication.

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
— mg/kg High
Production Forestry · Pristine Reference
OptimalRange Superseded v1