Soil Phosphorus

AUS-TDG-CON-SOP General Moderate confidence

Benchmark Value

8 mg/kg
Direction: Lower is desirable ↓
Form: Point

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

Using Colwell P method: A benchmark of approximately 8 mg/kg (0-10 cm depth) is recommended.

Metric Definition:

Available soil phosphorus concentration measured by Colwell P method at 0-10 cm soil depth.

Benchmark Definition:

This benchmark represents the recommended available soil phosphorus concentration in conservation areas of temperate dry woodlands and native grasslands, measured by the Colwell P method at 0-10 cm depth.

Justification:

Reflects P levels where native plant species occurrence peaked in ungrazed, low-P grassy ecosystems in central Victoria.

Sources (1)

Preview of Individual plant species responses to phosphorus and livestock grazing in temperate grassy ecosystems of Australia (Dorrough and Scroggie, 2008)
Individual plant species responses to phosphorus and livestock grazing in temperate grassy ecosystems of Australia (Dorrough and Scroggie, 2008) Journal

Individual plant species responses to phosphorus and livestock grazing in temperate grassy ecosystems of Australia. Australian Journal of Botany, 56(8), 663-673. (Dorrough, J., & Scroggie, M. P., 2008)

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

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)
Contextual Support Journal

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

View Source
Preview of Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025
Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025
Direct Evidence Government

Understanding soil tests for pastures

View Source

Context

  • Region Australia
  • Biome Temperate Dry Woodlands & Native Grasslands
  • Land Use Conservation / Protected Natural Areas
  • Assessment Conservation Target
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 24 Mar 2026

Notes

Lower Critical Threshold likely <2-3 mg/kg; Optimal Range Colwell P approximately 5-10 mg/kg; Upper Detrimental Threshold Colwell P >12-15 mg/kg; maintaining low Colwell P is crucial; avoid enrichment.