Soil Phosphorus

AUS-AKW-CON-SOP General Moderate confidence

Benchmark Value

2 mg/kg

Direction: Higher 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 7 benchmarks together — the OptimalRange form drives the primary score, while 6 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MaximumOnly Guard OptimalRange Guard MinimumOnly Guard MaximumOnly Guard OptimalRange Guard MinimumOnly Guard

Evidence & Context

typical virgin soils in P-impoverished south-west Australia have Colwell-P values of <2 mg/kg

Metric Definition:

Available phosphorus as measured by Colwell-P test indicating the critical low threshold below which ecosystem function is compromised.

Benchmark Definition:

This benchmark represents the lower critical threshold of available phosphorus below which native flora experience severe nutrient stress in the Arid Karstic Woodlands & Shrublands biome.

Justification:

The benchmark value is considered the floor for a functioning native system, supported by Queensland Government classification of 0-4 mg/kg as 'Acutely Deficient'.

Sources (1)

Preview of An inventory and condition survey of the Western Australian part of the Nullarbor region, accessed July 25, 2025

An inventory and condition survey of the Western Australian part of the Nullarbor region, accessed July 25, 2025 Journal

(PDF) Phosphorus status and saturation in soils that drain into the ...

View Source

Context

Region Australia
Biome Arid Karstic Woodlands & Shrublands
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 2
Effective From 25 Mar 2026

Notes

Represents the floor of a functioning system in P-impoverished native ecosystems.

Related Benchmarks

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