Soil pH — Benchmark Detail

Benchmark Value

5.5 pH

Thresholds: Lower: 5.5, Upper: —

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 19 benchmarks together — the OptimalRange form drives the primary score, while 18 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary OptimalRange Guard MinimumOnly Guard UpperThreshold Guard OptimalRange Guard LowerThreshold Guard OptimalRange Guard UpperThreshold Guard OptimalRange Guard LowerThreshold Guard UpperThreshold Guard MinimumOnly Guard LowerThreshold Guard OptimalRange Guard UpperThreshold Guard OptimalRange Guard LowerThreshold Guard UpperThreshold Guard OptimalRange Guard

Evidence & Context

A preventative management target of maintaining topsoil pHCaCl2 at or above 5.5 is widely recommended.

Metric Definition:

Topsoil pH measured in 0.01M CaCl2 solution

Benchmark Definition:

This benchmark defines the minimum soil pH level in 0.01M CaCl2 solution to prevent acid soil degradation and maintain productivity in Temperate Semi-Arid Shrublands & Open Woodlands under livestock grazing and pasture.

Justification:

Maintaining pH above 5.5 is crucial to prevent degradation associated with aluminium toxicity and productivity decline.

Sources (2)

Preview of NSW Environment Protection Authority. (2021). State of the Environment - Soil Condition 2021.

NSW Environment Protection Authority. (2021). State of the Environment - Soil Condition 2021. Government

Soil Acidity | Meat & Livestock Australia, accessed July 10, 2025,

View Source

SoilQuality.org.au. (n.d.). Soil Acidity Factsheet.

Soil Acidity | Fact Sheets | soilquality.org.au, accessed August 28, 2025,

View Source

Supporting Sources (5)

Additional references from the underlying research that informed this benchmark.

Preview of Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,

Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,

Direct Evidence Journal

Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations

View Source

Heavy grazing reduces soil bacterial diversity by increasing soil pH in a semi-arid steppe, accessed July 10, 2025,

Contextual Support Journal

Soil Acidity in the Mallee - Department for Environment and Water, accessed July 7, 2025,

View Source

Soil | Australia state of the environment 2021, accessed August 12, 2025,

Direct Evidence Journal

OzFlux-TERN GWW SuperSite presentation: Soil Chemical Properties

View Source

Soil Acidity - Ag Excellence Alliance, accessed July 10, 2025,

Contextual Support GreyLiterature

Soil pH and Microbial Life - Number Analytics, accessed July 7, 2025,

View Source

Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,

Direct Evidence Government

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

View Source

Context

Region Australia
Biome Temperate Semi-Arid Shrublands & Open Woodlands
Land Use Livestock Grazing & Pasture
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

No upper detrimental threshold — higher values are always better up to natural saturation. A pH below 5.0 indicates a problem acid soil with significant risk of aluminium toxicity.

Related Benchmarks

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