Soil Phosphorus

AUS-TDG-LVG-SOP General Moderate confidence

Benchmark Value

20 mg/kg
Thresholds: Lower: 20, Upper: —
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.

Evidence & Context

Victorian agricultural guidelines categorize Olsen P levels of 20 to 27 mg/kg as "Elevated," and levels >27 mg/kg as "Very high".

Metric Definition:

Available soil phosphorus measured as Olsen P in the 0-10 cm soil depth.

Benchmark Definition:

This benchmark sets a minimum Olsen P level in the 0-10 cm soil depth above which soil phosphorus is considered elevated, indicating potential ecological risk.

Justification:

Levels above this threshold are likely to reduce native diversity and increase weed invasion.

Sources (1)

Preview of What are the optimum nutrient targets for pastures?
What are the optimum nutrient targets for pastures? GreyLiterature

What are the optimum nutrient targets for pastures?

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

Preview of Over-fertilization diminishes the biodiversity of global grasslands - Mongabay
Over-fertilization diminishes the biodiversity of global grasslands - Mongabay
Contextual Support GreyLiterature

Over-fertilization diminishes the biodiversity of global grasslands - Mongabay

View Source
Preview of Phosphorus requirements of Australian native plants - ResearchGate, accessed August 4, 2025
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
Preview of Phosphorus responses of perennial native pasture species endemic to south-eastern Australia to P application: a review. Crop & Pasture Science, 71(9), 797-815. (Lodge, G. M., Murphy, S. R., & Harden, S., 2020)
Phosphorus responses of perennial native pasture species endemic to south-eastern Australia to P application: a review. Crop & Pasture Science, 71(9), 797-815. (Lodge, G. M., Murphy, S. R., & Harden, S., 2020)
Direct Evidence Journal

Phosphorus fertiliser management for pastures based on native grasses in south-eastern Australia

View Source
Preview of The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition - CSIRO Publishing, accessed August 5, 2025,
The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition - CSIRO Publishing, accessed August 5, 2025,
Contextual Support Journal

Crop and Pasture Science - CSIRO PUBLISHING

View Source

Context

  • Region Australia
  • Biome Temperate Dry Woodlands & Native Grasslands
  • Land Use Livestock Grazing & Pasture
  • Assessment Pristine Reference
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 25 Mar 2026

Notes

Olsen P levels of 20 to 27 mg/kg are 'Elevated' and >27 mg/kg are 'Very high', indicating potential ecological risk.

Related Benchmarks

Other benchmarks in the AUS-TDG-LVG-SOP family.

— mg/kg High
Livestock Grazing & Pasture · Pristine Reference
OptimalRange Active v1
6 mg/kg Moderate
Livestock Grazing & Pasture · Pristine Reference
MaximumOnly Active v1
8 mg/kg Moderate
Livestock Grazing & Pasture · Pristine Reference
MinimumOnly Active v1
6 mg/kg Moderate
Livestock Grazing & Pasture · Pristine Reference
MinimumOnly Active v1
— mg/kg Moderate
Livestock Grazing & Pasture · Pristine Reference
OptimalRange Active v1