Soil pH — Benchmark Detail

Benchmark Value

7.5 pH

Thresholds: Lower: —, Upper: 7.5

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 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

A practical upper detrimental threshold of pH(water) 7.5 is identified. Above this level, the risk of micronutrient deficiencies increases, and the system moves away from its natural chemical state with no corresponding gain in health or productivity.

Metric Definition:

Soil pH measured in water at a 1:5 soil to water ratio in the top 0-10 cm of soil.

Benchmark Definition:

The upper pH threshold beyond which micronutrient deficiencies and ecological harm occur in tropical and subtropical rainforest production forestry soils.

Justification:

Beyond this point, the availability of crucial micronutrients (e.g., zinc, copper) may become limited, and there are no additional ecological benefits to be gained in these naturally acidic systems.

Sources (1)

Preview of Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

Agriculture Victoria. (2024). Soil acidity.

Contextual Support

Soil acidity | Soil | Farm management - Agriculture Victoria, accessed August 28, 2025

View Source

Preview of Carbon and Nitrogen Mineralization in Relation to Soil Particle-Size Fractions after 32 Years of Chemical and Manure Application in a Continuous Maize Cropping System, accessed July 19, 2025

Carbon and Nitrogen Mineralization in Relation to Soil Particle-Size Fractions after 32 Years of Chemical and Manure Application in a Continuous Maize Cropping System, accessed July 19, 2025

Direct Evidence Journal

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia - ResearchGate, accessed July 20, 2025

View Source

Preview of Multiple soil element and pH interactions constrain plant performance on tropical soils with a long history of fire - CSIRO PUBLISHING | Soil Research, accessed May 16, 2025,

Multiple soil element and pH interactions constrain plant performance on tropical soils with a long history of fire - CSIRO PUBLISHING | Soil Research, accessed May 16, 2025,

Contextual Support Journal

Multiple soil element and pH interactions constrain plant performance on tropical soils with a long history of fire - CSIRO PUBLISHING | Soil Research, accessed July 20, 2025

View Source

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

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Production Forestry
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 25 Mar 2026

Notes

Upper Detrimental Threshold: 7.5 pH. This threshold is based on horticultural guidelines and ecological considerations for tropical and subtropical rainforest soils.

Related Benchmarks

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