Soil Phosphorus

AUS-TMI-FOR-SOP General Moderate confidence

Benchmark Value

200 mg/kg

Thresholds: Lower: —, Upper: 200

Direction: Higher is desirable ↑

Form: UpperThreshold

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 16 benchmarks together — the OptimalRange form drives the primary score, while 15 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard LowerThreshold Guard UpperThreshold Guard LowerThreshold Guard MinimumOnly Guard OptimalRange Guard LowerThreshold Guard OptimalRange Guard UpperThreshold Guard Point Guard OptimalRange Guard MinimumOnly Guard Point Guard LowerThreshold Guard OptimalRange Guard

Evidence & Context

An Upper Detrimental Threshold is proposed at >200 mg/kg Total P. This level, significantly exceeding the natural background (95th percentile), does not indicate toxicity to the plantation species but rather signifies a degraded state due to over-fertilisation, posing a significant nutrient runoff risk to adjacent, P-sensitive native ecosystems.

Metric Definition:

Total Phosphorus concentration in soil

Benchmark Definition:

This benchmark represents the upper detrimental threshold of soil phosphorus above which ecological risk from over-fertilization occurs in the tropical and subtropical maritime island production forestry biome.

Justification:

Defined by the 95th percentile natural background; values above indicate degraded state and risk of nutrient runoff.

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

Cycling of phosphorus in grazing systems - NSW Department of Primary Industries

View Source

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

Contextual Support Journal

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

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

Plantation Forestry and Economic Development in the Tiwi Islands - This document is discoverable and free to researchers across the globe due to the work of AgEcon Search. Help ensure our sustain

View Source

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

Contextual Support Journal

The Big Phosphorus Issue - Australian Native Plants — The Gardeners Lodge, accessed August 1, 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, accessed July 19, 2025,

View Source

Context

Region Australia
Biome Tropical & Subtropical Maritime Islands
Land Use Production Forestry
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 25 Mar 2026

Notes

Upper Detrimental Threshold: 200 mg/kg. Not a toxicity threshold for plantation species but an ecological risk threshold for adjacent native ecosystems.

Related Benchmarks

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