Soil pH

AUS-AMR-CON-SPH General High confidence

Benchmark Value

8.5 pH
Thresholds: Lower: —, Upper: 8.5
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 10 benchmarks together — the OptimalRange form drives the primary score, while 9 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Upper Detrimental Threshold: pHCaCl2​​ 8.5

Metric Definition:

Upper Detrimental Threshold of soil pH measured in 0.01M Calcium Chloride (pHCaCl2​​)

Benchmark Definition:

This benchmark defines the upper pH threshold beyond which soil alkalinity likely causes significant negative impacts on ecosystem function in the Arid Mountain Ranges & Uplands biome.

Justification:

This value can be used to define the point at which alkalinity is likely to be associated with significant negative impacts on ecosystem function, moving beyond a state of natural health.

Sources (1)

Preview of The pH of Australian soils: field results from a national survey
The pH of Australian soils: field results from a national survey Journal

The pH of Australian soils: field results from a national survey

View Source

Supporting Sources (15)

Additional references from the underlying research that informed this benchmark.

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

Soil pH | Environment, land and water - Queensland Government, accessed August 28, 2025,

View Source
Preview of Al-Beidh, S., & Al-Tawaha, A. R. M. (2023). Basic Properties and Mineralogy of Soils and Their Impact on the Growth of Jarrah Forest in Southwestern Australia. Land, 12(6), 1236.
Al-Beidh, S., & Al-Tawaha, A. R. M. (2023). Basic Properties and Mineralogy of Soils and Their Impact on the Growth of Jarrah Forest in Southwestern Australia. Land, 12(6), 1236.
Contextual Support Journal

Soil Characteristics and Fertility of the Unique Jarrah Forest of Southwestern Australia, with Particular Consideration of Plant Nutrition and Land Rehabilitation - MDPI, accessed July 19, 2025,

View Source
Preview of ARID LANDS OF AUSTRALIA - Open Research Repository
ARID LANDS OF AUSTRALIA - Open Research Repository
Contextual Support Government

ARID LANDS OF AUSTRALIA - Open Research Repository

View Source
Preview of ARID LANDS OF AUSTRALIA - Open Research Repository, accessed July 15, 2025,
ARID LANDS OF AUSTRALIA - Open Research Repository, accessed July 15, 2025,
Contextual Support Journal

ARID LANDS OF AUSTRALIA - ANU Open Research, accessed July 22, 2025

View Source
Preview of Australia - Soils, Climate, Erosion | Britannica
Australia - Soils, Climate, Erosion | Britannica
Contextual Support GreyLiterature

SOIL TESTING, accessed August 1, 2025

View Source
Preview of Land | State of the Environment Report 2011
Land | State of the Environment Report 2011
Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 28, 2025,

View Source
Preview of Soil and Landscape Grid National Soil Attribute Maps - pH (Water) (3" resolution) - Release 1
Soil and Landscape Grid National Soil Attribute Maps - pH (Water) (3" resolution) - Release 1
Contextual Support Government

Soil and Landscape Grid National Soil ... - CSIRO Data Access Portal

View Source
Preview of Soil and Landscape Grid of Australia - CSIRO
Soil and Landscape Grid of Australia - CSIRO
Methodology Source Government

Soil and Landscape Grid of Australia - CSIRO

View Source
Preview of Soil and Landscape Grid of Australia - esoil.io, accessed July 13, 2025
Soil and Landscape Grid of Australia - esoil.io, accessed July 13, 2025
Methodology Source Government

Soil and Landscape Grid of Australia - esoil.io, accessed July 26, 2025,

View Source
Preview of Soil Constraints in an Arid Environment—Challenges, Prospects, and Implications - MDPI, accessed July 6, 2025,
Soil Constraints in an Arid Environment—Challenges, Prospects, and Implications - MDPI, accessed July 6, 2025,
Contextual Support Journal

Soil pH | Environment, land and water - Queensland Government, accessed July 28, 2025

View Source
Preview of Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,
Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,
Contextual Support Government

Improving Soil Structure and pH Levels (DPIFM_NT) - Department of ..., accessed July 20, 2025

View Source
Preview of TJORITJA / WEST MACDONNELL NATIONAL PARK - Department of Tourism and Hospitality
TJORITJA / WEST MACDONNELL NATIONAL PARK - Department of Tourism and Hospitality
Contextual Support Government

TJORITJA / WEST MACDONNELL NATIONAL PARK - Department of Tourism and Hospitality

View Source
Preview of Tool 6.7 Soil health benchmarks and guidelines for managing problem soils
Tool 6.7 Soil health benchmarks and guidelines for managing problem soils
Contextual Support Journal

Tool 6.7 Soil health benchmarks and guidelines for managing problem soils

View Source
Preview of Vulkathunha-Gammon Ranges National Park
Vulkathunha-Gammon Ranges National Park
Contextual Support Journal

Vulkathunha-Gammon Ranges National Park

View Source
Preview of World salinization with emphasis on Australia | Journal of Experimental Botany
World salinization with emphasis on Australia | Journal of Experimental Botany
Contextual Support Government

World salinization with emphasis on Australia | Journal of Experimental Botany

View Source

Context

  • Region Australia
  • Biome Arid Mountain Ranges & Uplands
  • Land Use Conservation / Protected Natural Areas
  • Assessment Pristine Reference
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 2
  • Effective From 19 Mar 2026

Notes

Above this level, soil function is likely compromised due to severe micronutrient limitations and a high probability of associated sodicity, which causes soil structural collapse.

Related Benchmarks

Other benchmarks in the AUS-AMR-CON-SPH family.

— pH High
Conservation / Protected Natural Areas · Pristine Reference
OptimalRange Active v4
4.5 pH High
Conservation / Protected Natural Areas · Pristine Reference
LowerThreshold Active v2
— pH High
Conservation / Protected Natural Areas · Pristine Reference
OptimalRange Superseded v3
— pH High
Conservation / Protected Natural Areas · Pristine Reference
OptimalRange Superseded v2
8.5 pH High
Conservation / Protected Natural Areas · Pristine Reference
UpperThreshold Superseded v1
— pH High
Conservation / Protected Natural Areas · Pristine Reference
OptimalRange Superseded v1
4.5 pH High
Conservation / Protected Natural Areas · Pristine Reference
LowerThreshold Superseded v1