Soil Potassium

AUS-TDG-FOR-SOK General Moderate confidence

Benchmark Value

74.1 mg/kg
Range: 70 to 79.5 mg/kg
Thresholds: Lower: 50, Upper: 120
Optimal Range: 70 to 79.5
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.

Evidence & Context

In this study, "intact forest" areas, characterized by higher ectomycorrhizal (ECM) fungal diversity and lower incidence of canker disease, exhibited significantly lower soil potassium concentrations (mean: 74.1±5.4 mg/kg) compared to "disturbed edge" habitats (mean: 103.8±8.1 mg/kg), which showed lower ECM diversity and higher disease incidence.

Metric Definition:

Soil potassium concentration measured as Colwell-K or equivalent extractable potassium in mg/kg.

Benchmark Definition:

Soil potassium concentration representing the best available condition of nature in sustainably managed production forestry in Australian Temperate Dry Woodlands & Native Grasslands.

Justification:

The value is derived from a peer-reviewed study linking soil potassium levels to ecological health indicators in a relevant Australian temperate eucalypt woodland. It represents a high environmental health condition though not explicitly from production forestry stands.

Sources (1)

Preview of Sapsford, S. J., Paap, T., Hardy, G. E. St. J., & Burgess, T. I. (2021). Anthropogenic Disturbance Impacts Mycorrhizal Communities and Abiotic Soil Properties: Implications for an Endemic Forest Disease. Frontiers in Forests and Global Change, 3, 593243.
Sapsford, S. J., Paap, T., Hardy, G. E. St. J., & Burgess, T. I. (2021). Anthropogenic Disturbance Impacts Mycorrhizal Communities and Abiotic Soil Properties: Implications for an Endemic Forest Disease. Frontiers in Forests and Global Change, 3, 593243. Journal

Sapsford, S. J., Paap, T., Hardy, G. E. St. J., & Burgess, T. I. (2021). Anthropogenic Disturbance Impacts Mycorrhizal Communities and Abiotic Soil Properties: Implications for an Endemic Forest Disease. Frontiers in Forests and Global Change, 3, 593243.

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Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

Preview of Agriculture Victoria. (2024). Understanding soil tests for pastures.
Agriculture Victoria. (2024). Understanding soil tests for pastures.
Contextual Support Government

Agriculture Victoria. (2024). Understanding soil tests for pastures.

View Source
Preview of Daws, M. I., Standish, R. J., Grigg, A. H., Morald, T. K., & Tibbett, M. (2021). Seeing the forest for the trees: fertiliser increases tree growth but decreases understorey diversity in the Northern Jarrah Forest, southwest Australia. Journal of the Royal Society of Western Australia, 104, 5-9.
Daws, M. I., Standish, R. J., Grigg, A. H., Morald, T. K., & Tibbett, M. (2021). Seeing the forest for the trees: fertiliser increases tree growth but decreases understorey diversity in the Northern Jarrah Forest, southwest Australia. Journal of the Royal Society of Western Australia, 104, 5-9.
Contextual Support Journal

Daws, M. I., Standish, R. J., Grigg, A. H., Morald, T. K., & Tibbett, M. (2021). Seeing the forest for the trees: fertiliser increases tree growth but decreases understorey diversity in the Northern Jarrah Forest, southwest Australia. Journal of the Royal Society of Western Australia, 104, 5-9.

View Source
Preview of Restoring Australia's temperate grasslands and grassy woodlands | Request PDF - ResearchGate, accessed August 6, 2025,
Restoring Australia's temperate grasslands and grassy woodlands | Request PDF - ResearchGate, accessed August 6, 2025,
Contextual Support Journal

Prober, S. M., Thiele, K. R., & Loneragan, W. A. (2005). Relationships among soil fertility, native plant diversity and exotic plant abundance inform restoration of forb-rich eucalypt woodlands. Austral Ecology, 30(6), 607-618.

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
Contextual Support Government

Understanding soil tests for pastures

View Source

Context

  • Region Australia
  • Biome Temperate Dry Woodlands & Native Grasslands
  • Land Use Production Forestry
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

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

Notes

Lower Critical Threshold: 50 mg/kg. Upper Detrimental Threshold: 120 mg/kg. Higher potassium levels in disturbed sites suggest that elevated K may indicate disturbance rather than better ecological health. The benchmark fits within a broader optimal range of 70-120 mg/kg for sandy/loamy soils and 1-5% K saturation of CEC. Levels above 100-120 mg/kg may indicate nutrient imbalance unfavorable to native biodiversity. [Migration] Original wider evidence range: 68.7 – 80 (retained OptimalRange: 70 – 79.5)

Related Benchmarks

Other benchmarks in the AUS-TDG-FOR-SOK family.

— mg/kg Moderate
Production Forestry · Pristine Reference
OptimalRange Active v2
120 mg/kg Moderate
Production Forestry · Pristine Reference
MaximumOnly Active v1
50 mg/kg Moderate
Production Forestry · Pristine Reference
LowerThreshold Active v1
80 mg/kg Moderate
Production Forestry · Pristine Reference
LowerThreshold Active v1
120 mg/kg Moderate
Production Forestry · Pristine Reference
UpperThreshold Active v1
74.1 mg/kg Moderate
Production Forestry · Pristine Reference
Point Active v1
— mg/kg Moderate
Production Forestry · Pristine Reference
OptimalRange Superseded v1