Soil Phosphorus

AUS-TMS-CON-SOP General Moderate confidence

Benchmark Value

5 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.

Evidence & Context

The proposed benchmark reference value for available phosphorus (Bicarbonate-extractable P, 0-10 cm depth) in well-conserved Australian TMS is generally < 5 mg/kg.

Metric Definition:

Available phosphorus (Bicarbonate-extractable P, 0-10 cm depth) in soil

Benchmark Definition:

This benchmark represents the upper limit of available phosphorus in well-conserved soils of the Australian Tropical Monsoonal Savannas, reflecting naturally low phosphorus levels that support healthy native savanna ecosystems.

Justification:

Reflects the P status of soils supporting healthy, native savanna ecosystems adapted to low nutrient availability.

Sources (1)

Preview of www.publications.qld.gov.au, accessed May 16, 2025,

www.publications.qld.gov.au, accessed May 16, 2025, Journal

The Soils of Cape York Peninsula. Cooktown and Weipa Sections. Land Resource Survey and Evaluation.

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

Management practices in the Northern Jarrah Forest, southwest Australia: fertiliser increases tree growth but decreases understo

Direct Evidence Journal

Management practices in the Northern Jarrah Forest, southwest Australia: fertiliser increases tree growth but decreases understo

View Source

Phosphorus toxicity in the Proteaceae - ResearchGate

Contextual Support Journal

Phosphorus toxicity in the Proteaceae - ResearchGate

View Source

Context

Region Australia
Biome Tropical Monsoonal Savannas
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Lower Critical Threshold: 1 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The benchmark reflects the naturally low available phosphorus levels characteristic of ancient, weathered soils in Australian Tropical Monsoonal Savannas (TMS) under conservation. High environmental health in these P-limited ecosystems is associated with this oligotrophic state, to which native flora is highly adapted.

Related Benchmarks

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