Soil pH — Benchmark Detail

Benchmark Value

5 pH

Thresholds: Lower: 5, Upper: —

Direction: Higher is desirable ↑

Form: LowerThreshold

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 16 benchmarks together — the OptimalRange form drives the primary score, while 15 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Based on this clear, evidence-based progression of functional decline, a Lower Critical Threshold of pH (CaCl2) 5.0 is established.

Metric Definition:

Lower critical threshold for soil pH measured in calcium chloride (CaCl2) solution

Benchmark Definition:

This benchmark defines the lower critical soil pH threshold measured in calcium chloride solution below which ecosystem functions are significantly compromised in temperate semi-arid shrublands and open woodlands under production forestry in Australia.

Justification:

This value represents a conservative boundary below which multiple, critical ecosystem functions are known to be significantly compromised.

Sources (1)

Preview of Government of South Australia, Department for Environment and Water. (n.d.). Soil Health and Condition.

Government of South Australia, Department for Environment and Water. (n.d.). Soil Health and Condition. Government

Soil acidity - Department for Environment and Water, accessed July 30, 2025,

View Source

Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

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

Direct Evidence Journal

OzFlux-TERN GWW SuperSite presentation: Soil Chemical Properties

View Source

Context

Region Australia
Biome Temperate Semi-Arid Shrublands & Open Woodlands
Land Use Production Forestry
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Below this threshold, nutrient availability, microbial function, and root health are significantly compromised.

Related Benchmarks

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