Soil pH — Benchmark Detail

Benchmark Value

8.5 pH

Direction: Higher is desirable ↑

Form: MaximumOnly

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.

Evidence & Context

Upper Detrimental Threshold: While some savanna soils are naturally alkaline, an increase in pHw significantly above the natural range for a given soil type (e.g., exceeding pHw ~7.5 on typically acidic/neutral soils, or pHw >8.5-9.0 generally, particularly if induced by disturbances like tree clearing) can be detrimental.

Metric Definition:

Soil pH measured in a 1:5 soil:water suspension (pHw)

Benchmark Definition:

Upper detrimental soil pH threshold above which ecosystem health is negatively impacted.

Justification:

Very high pH levels can cause severe micronutrient deficiencies and sodicity issues, disrupting natural ecosystem balance.

Sources (1)

Preview of Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,

Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025, Government

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 17, 2025

View Source

Supporting Sources (37)

Additional references from the underlying research that informed this benchmark.

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S11

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S11, S8

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S2, S8

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S2, S8

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S2, S8

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S2, S8

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S2, S8

S46, S25

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S46, S25

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Preview of Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil heal - alice Embrapa, accessed July 28, 2025,

Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil heal - alice Embrapa, accessed July 28, 2025,

Contextual Support Journal

www.barenbrug.com.au, accessed May 13, 2025,

View Source

Preview of Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories - OPUS at UTS, accessed May 16, 2025,

Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories - OPUS at UTS, accessed May 16, 2025,

Contextual Support Journal

opus.lib.uts.edu.au

View Source

Soil Quality and Its Management in Humid Subtropical and Tropical Environments - UKnowledge, accessed May 15, 2025,

Contextual Support

Soil Quality and Its Management in Humid Subtropical and Tropical Environments - UKnowledge

View Source

Preview of Soil surface pH DSM data of the Southern Gulf catchments (NT and Qld) generated by the Southern Gulf Water Resource Assessment - CSIRO Data Access Portal, accessed May 13, 2025,

Soil surface pH DSM data of the Southern Gulf catchments (NT and Qld) generated by the Southern Gulf Water Resource Assessment - CSIRO Data Access Portal, accessed May 13, 2025,

Contextual Support Government

Gibbons, P., & Sharp, A. (2015). Impacts of warming and fire on soil moisture and available nutrients in a sub-alpine heathland. Climate Research, 64, 159-170.

View Source

Tropical Pasture - Barenbrug Australia, accessed July 18, 2025,

Direct Evidence Journal

P.PSH.1050 – Phosphorus management and requirements of tropical legume pasture swards - MLA, accessed July 18, 2025

View Source

Context

Region Australia
Biome Tropical Monsoonal Savannas
Land Use Livestock Grazing & Pasture
Assessment Conservation Target
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 1 Jun 2026

Notes

This threshold is especially relevant if pH increase is induced by disturbances like tree clearing.

Related Benchmarks

Other benchmarks in the AUS-TMS-LVG-SPH family.