Soil pH — Benchmark Detail

Benchmark Value

4.5 pH

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 2 benchmarks together — the OptimalRange form drives the primary score, while 1 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard

Evidence & Context

Lower Critical Soil pH (1:5 soil:water) Threshold: < pH 4.5.

Metric Definition:

Soil pH measured as a 1:5 soil:water suspension.

Benchmark Definition:

This benchmark sets a lower critical soil pH threshold of 4.5 for production forestry in the Alpine and Subalpine Complex biome, below which significant negative impacts on tree health and soil biological processes occur.

Justification:

Significant risk of Al/Mn toxicity; reduced availability of P, Ca, Mg, Mo; impaired N cycling and microbial activity; potential for severe decline in tree health and productivity.

Sources (1)

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, 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

Context

Region Australia
Biome Alpine and Subalpine Complex
Land Use Production Forestry
Assessment Production Forestry
Vegetation Forest
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 9 Jun 2026

Notes

Represents a threshold below which significant negative impacts on tree health and soil biological processes become evident.

Related Benchmarks

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