Soil Phosphorus

AUS-TMI-FOR-SOP General Moderate confidence

Benchmark Value

60 mg/kg

Direction: Higher 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 14 benchmarks together — the OptimalRange form drives the primary score, while 13 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

A Total P concentration of < 60 mg/kg can be considered indicative of a critically low level for this production system, where P is a primary limiting factor to ecological function and productivity.

Metric Definition:

Lower critical threshold of Total Phosphorus concentration below which productivity is compromised

Benchmark Definition:

Lower critical threshold for soil phosphorus indicating deficiency in Tropical & Subtropical Maritime Islands production forestry soils.

Justification:

Derived from the 5th percentile of natural variation in the landscape, representing the most P-impoverished soils where growth is limited.

Sources (1)

Soil and Landscape Grid National Soil Attribute Maps - Total Phosphorus (3" resolution) - Release 2 - CSIRO Data Access Portal Government

Soil and Landscape Grid National Soil Attribute Maps - Total Phosphorus (3" resolution) - Release 2

View Source

Supporting Sources (6)

Additional references from the underlying research that informed this benchmark.

A simple phosphorus buffering index for Australian soils - University of Tasmania Open Access Repository Cover sheet

Contextual Support GreyLiterature

Phosphorus - NSW | Fact Sheets | soilquality.org.au, accessed July 22, 2025

View Source

BIODIVERSITY CONSERVATION ON THE TIWI ISLANDS, NORTHERN TERRITORY: Part 1. Environments and plants, accessed July 30, 2025,

Contextual Support Journal

Plantation Forestry and Economic Development in the Tiwi Islands

View Source

Preview of Eucalyptus pellita substantially outperforms Acacia mangium in tropical savannah ecosystem of Australia, but strategies are needed to maintain soil nutrients - Find an Expert - The University of Melbourne

Eucalyptus pellita substantially outperforms Acacia mangium in tropical savannah ecosystem of Australia, but strategies are needed to maintain soil nutrients - Find an Expert - The University of Melbourne

Contextual Support Journal

View Source

Norfolk Island Subtropical Forests | One Earth, accessed July 30, 2025,

Contextual Support

Conservation | Norfolk Island National Park | Parks Australia, accessed August 2, 2025

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Phosphorus requirements of Australian native plants - ResearchGate, accessed August 4, 2025

Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed July 22, 2025

View Source

Phosphorus: a finite resource essential for life, critical for agriculture and food security - CSIRO, accessed August 11, 2025

Contextual Support Government

Nitrogen and Phosphorus Retranslocation of Leaves and Stemwood in a Mature Eucalyptus Forest Exposed to 5 Years of Elevated CO2 - Frontiers

View Source

Context

Region Australia
Biome Tropical & Subtropical Maritime Islands
Land Use Production Forestry
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Soils at or below this level represent a state of deficiency where plantation growth is likely severely limited by P availability. No upper detrimental threshold — higher values are always better up to natural saturation. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-TMI-FOR-SOP family.