Soil Phosphorus

AUS-AKW-CON-SOP General Moderate confidence

Benchmark Value

20 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 11 benchmarks together — the OptimalRange form drives the primary score, while 10 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

a value of approximately 20 mg/kg Colwell-P is proposed as the upper detrimental threshold

Metric Definition:

Upper detrimental threshold for available phosphorus (Colwell-P) beyond which native species displacement occurs.

Benchmark Definition:

This benchmark marks the phosphorus level at which native perennial species begin to be displaced by more phosphorus-responsive species, indicating eutrophication risk in the Arid Karstic Woodlands & Shrublands biome.

Justification:

Based on agricultural research indicating native perennial grasses decline above this level.

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 Conservation Target
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Indicates terrestrial eutrophication and loss of conservation value.

Related Benchmarks

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