Soil pH

AUS-TDG-FOR-SPH General Moderate confidence

Benchmark Value

4.8 pH (CaCl₂)
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 13 benchmarks together — the OptimalRange form drives the primary score, while 12 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

A soil pH (CaCl₂) value below 4.8 is proposed as a lower critical threshold.

Metric Definition:

Soil pH measured in a 1:5 soil to 0.01M CaCl₂ solution, indicating acidity level below which aluminium and manganese toxicity and nutrient deficiencies impair ecosystem health.

Benchmark Definition:

Lower critical soil pH threshold below which soil toxicity and nutrient availability issues cause ecosystem degradation.

Justification:

Below pHCa 4.8, aluminium and manganese toxicity increase, nutrient availability decreases, and microbial activity is impaired, compromising ecosystem health.

Sources (1)

Preview of Agriculture Victoria. (2024). Soil acidity.
Agriculture Victoria. (2024). Soil acidity. Government

Agriculture Victoria. (2025). Soil acidity. Farm Management.

View Source

Supporting Sources (22)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Determining reference conditions for management and ..., accessed August 5, 2025,
(PDF) Determining reference conditions for management and ..., accessed August 5, 2025,
Direct Evidence Journal

Effects of Stock Grazing on Biodiversity Values in Temperate Native Grasslands and Grassy Woodlands in SE Australia: A Literature Review - ACT Government

View Source
Preview of (PDF) Determining reference conditions for management and ..., accessed May 15, 2025
(PDF) Determining reference conditions for management and ..., accessed May 15, 2025
Direct Evidence

(PDF) Determining reference conditions for management and ..., accessed May 15, 2025

View Source
Preview of (PDF) The pH of Australian soils: field results from a national survey - ResearchGate, accessed July 25, 2025,
(PDF) The pH of Australian soils: field results from a national survey - ResearchGate, accessed July 25, 2025,
Direct Evidence Journal

Caritat, P. de, & Cooper, M. (2011). The pH of Australian soils: Field results from a national survey. Soil Research, 49, 172-182.

View Source
Preview of Analysing the Impact of Harvesting Methods on the Quantity of Harvesting Residues: An Australian Case Study - USC Research Bank, accessed May 15, 2025
Analysing the Impact of Harvesting Methods on the Quantity of Harvesting Residues: An Australian Case Study - USC Research Bank, accessed May 15, 2025
Contextual Support Journal

Nutrient cycling in age sequences of two Eucalyptus plantation species - ResearchGate, accessed May 15, 2025

View Source
Preview of Australia's Native Vegetation Framework - DAFF, accessed August 6, 2025,
Australia's Native Vegetation Framework - DAFF, accessed August 6, 2025,
Contextual Support Journal

risks and impacts of plant industries on soil condition - Department of Agriculture and Fisheries

View Source
Preview of Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,
Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,
Contextual Support Journal

How should we manage our soils to increase soil carbon?, accessed May 10, 2026

View Source
Preview of Characterisation of dissolved organic matter in water extracts of thermally altered plant species found in box–ironbark forests | Request PDF - ResearchGate, accessed May 15, 2025
Characterisation of dissolved organic matter in water extracts of thermally altered plant species found in box–ironbark forests | Request PDF - ResearchGate, accessed May 15, 2025
Contextual Support GreyLiterature

(PDF) Impact of tree clearing on soil pH and nutrient availability in ..., accessed May 15, 2025

View Source
Preview of Envirocrops. (n.d.). Eucalyptus Best Practice Guidelines.
Envirocrops. (n.d.). Eucalyptus Best Practice Guidelines.
Contextual Support GreyLiterature

How-to Guide: Best Practices For Eucalyptus Timber Harvesting, accessed May 15, 2025

View Source
Preview of Eucalyptus obliqua seedling growth in organic vs. mineral ... - Frontiers, accessed May 15, 2025
Eucalyptus obliqua seedling growth in organic vs. mineral ... - Frontiers, accessed May 15, 2025
Contextual Support GreyLiterature

Eucalyptus obliqua seedling growth in organic vs. mineral ... - Frontiers, accessed May 15, 2025

View Source
Preview of Healthy Soils for Sustainable Farms | FutureBeef
Healthy Soils for Sustainable Farms | FutureBeef
Contextual Support Journal

Healthy Soils for Sustainable Farms | FutureBeef, accessed August 4, 2025,

View Source
Preview of Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Contextual Support GreyLiterature

(PDF) Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 4, 2025,

View Source
Preview of Impact of tree clearing on soil pH and nutrient availability in grazing systems of central Queensland, Australia - ResearchGate, accessed July 23, 2025
Impact of tree clearing on soil pH and nutrient availability in grazing systems of central Queensland, Australia - ResearchGate, accessed July 23, 2025
Contextual Support GreyLiterature

Ecological, Economic and Social Effects of Eucalyptus - Food and Agriculture Organization of the United Nations, accessed May 15, 2025

View Source
Preview of Keith, H., et al. (2009). The impact of harvesting native forests on vegetation and soil C stocks and soil CO2, N2O and CH4 fluxes. Australian Forestry, 72(4), 183-194.
Keith, H., et al. (2009). The impact of harvesting native forests on vegetation and soil C stocks and soil CO2, N2O and CH4 fluxes. Australian Forestry, 72(4), 183-194.
Contextual Support GreyLiterature

The impact of harvesting native forests on vegetation and soil C stocks, and soil CO2, N2O and CH4 fluxes - ResearchGate, accessed May 15, 2025

View Source
Preview of National Soil Strategy - DAFF, accessed May 15, 2025
National Soil Strategy - DAFF, accessed May 15, 2025
Contextual Support Journal

Scattered paddock trees, litter chemistry, and surface soil properties in pastures of the New England Tablelands, New South Wales - CSIRO Publishing, accessed May 15, 2025

View Source
Preview of Nitrogen use efficiency and nitrogen balance in Australian farmlands - Agronomy Australia Proceedings, accessed May 11, 2025
Nitrogen use efficiency and nitrogen balance in Australian farmlands - Agronomy Australia Proceedings, accessed May 11, 2025
Contextual Support GreyLiterature

Nitrogen use efficiency and nitrogen balance in Australian farmlands - Agronomy Australia Proceedings, accessed May 11, 2025

View Source
Preview of NSW Department of Primary Industries. (2021). Soil Acidity and Liming (AC.19).
NSW Department of Primary Industries. (2021). Soil Acidity and Liming (AC.19).
Contextual Support Government

Understanding soil pH

View Source
Preview of Prober, S.M., Thiele, K.R., & Lunt, I.D. (2002). Determining reference conditions for management and restoration of temperate grassy woodlands: relationships among trees, topsoils and understorey flora in little-grazed remnants. Australian Journal of Botany, 50(6), 687-697.
Prober, S.M., Thiele, K.R., & Lunt, I.D. (2002). Determining reference conditions for management and restoration of temperate grassy woodlands: relationships among trees, topsoils and understorey flora in little-grazed remnants. Australian Journal of Botany, 50(6), 687-697.
Contextual Support Journal

Prober, S.M., Thiele, K.R., & Lunt, I.D. (2002). Determining reference conditions for management and restoration of temperate grassy woodlands: relationships among trees, topsoils and understorey flora in little-grazed remnants. Australian Journal of Botany, 50(6), 687-697.

View Source
Preview of Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns | Request PDF - ResearchGate, accessed May 12, 2025
Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns | Request PDF - ResearchGate, accessed May 12, 2025
Contextual Support GreyLiterature

Increasing and declining native species in urban remnant grasslands respond differently to nitrogen addition and disturbance

View Source
Preview of Review of C:N Ratios in Vegetation, Litter and Soil Under Australian Native Forests and Plantations - DCCEEW
Review of C:N Ratios in Vegetation, Litter and Soil Under Australian Native Forests and Plantations - DCCEEW
Contextual Support Journal

Review of C:N Ratios in Vegetation, Litter and Soil ... - DCCEEW

View Source
Preview of Soil Research - CSIRO PUBLISHING, accessed July 16, 2025,
Soil Research - CSIRO PUBLISHING, accessed July 16, 2025,
Contextual Support Journal

Soil Research - CSIRO PUBLISHING, accessed August 11, 2025,

View Source
Preview of Temperate forests and soils [Chapter 6], accessed May 15, 2025
Temperate forests and soils [Chapter 6], accessed May 15, 2025
Contextual Support GreyLiterature

Temperate forests and soils [Chapter 6], accessed May 15, 2025

View Source
Preview of Temperate Grasslands - Greening Australia, accessed August 4, 2025
Temperate Grasslands - Greening Australia, accessed August 4, 2025
Contextual Support Direct Evidence Journal

Plant nutrients in the soil - NSW Department of Primary Industries

View Source

Context

  • Region Australia
  • Biome Temperate Dry Woodlands & Native Grasslands
  • Land Use Production Forestry
  • Assessment Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 10 Jun 2026

Notes

Represents a critical threshold for soil acidity beyond which ecosystem function and productivity are broadly compromised. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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

— pH (CaCl₂) Moderate
Production Forestry · Not Stated
OptimalRange Active v1
6.5 pH (CaCl₂) Moderate
Production Forestry · Not Stated
MaximumOnly Active v1