Soil Phosphorus

AUS-AKW-CON-SOP General Moderate confidence

Benchmark Value

20 mg/kg

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 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

it becomes increasingly difficult to retain native perennial grasses once phosphorus levels exceeded 20 Colwell P

Metric Definition:

Available phosphorus as measured by Colwell-P test indicating the level at which ecological integrity is lost due to nutrient enrichment.

Benchmark Definition:

This benchmark represents the upper detrimental threshold of available phosphorus beyond which native species are displaced in the Arid Karstic Woodlands & Shrublands biome.

Justification:

Based on agricultural research proxy indicating competitive exclusion of native species 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 25 Mar 2026

Notes

Indicates terrestrial eutrophication and loss of native ecosystem character.

Related Benchmarks

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