Soil pH — Benchmark Detail

Benchmark Value

4.8 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 13 benchmarks together — the OptimalRange form drives the primary score, while 12 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard MaximumOnly Guard OptimalRange Guard MinimumOnly Guard MaximumOnly Guard OptimalRange Guard MinimumOnly Guard MaximumOnly Guard Point Guard OptimalRange Guard MinimumOnly Guard MaximumOnly Guard

Evidence & Context

Considering these factors, a lower critical threshold of pH_CaCl2 4.8 is proposed for production forestry in Australian Tropical Monsoonal Savannas.

Metric Definition:

Lower critical threshold of soil pH measured in 0.01M calcium chloride below which significant detrimental impacts occur.

Benchmark Definition:

Critical lower soil pH threshold below which aluminium toxicity and nutrient limitations impair plant growth and soil functions.

Justification:

Strong and consistent evidence from Australian studies indicates pH_CaCl2 below 4.8 is associated with aluminium toxicity and nutrient deficiencies.

Supporting Sources (7)

Additional references from the underlying research that informed this benchmark.

(PDF) Soil acidification and natural resource management ..., accessed May 16, 2025,

Contextual Support GreyLiterature

(PDF) Soil acidification and natural resource management ..., accessed May 16, 2025

View Source

(PDF) The pH of Australian soils: field results from a national survey - ResearchGate, accessed July 25, 2025,

Contextual Support 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

Helyar Porter (1989) Soil acidification, its measurement and the processes involved (in S8)

Direct Evidence

Kaur et al. (2005) Impact of tree clearing on soil pH.

View Source

Horiba (2018) Soil pH and Nutrient Availability

Methodology Source GreyLiterature

Soil Acidity - Land degradation in Australia, 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 Direct Evidence Journal

Soil Research - CSIRO PUBLISHING

View Source

Preview of Using digital photography to monitor changes in biocrusts and ground cover in a savanna rangeland - CSIRO Publishing, accessed May 16, 2025,

Using digital photography to monitor changes in biocrusts and ground cover in a savanna rangeland - CSIRO Publishing, accessed May 16, 2025,

Contextual Support Methodology Source Journal

Hunt, L. P., Petty, S., Cowley, R., Fisher, A., Ash, A., & MacDonald, N. (2014). Principles and guidelines for managing cattle grazing in the grazing lands of northern Australia: stocking rates, pasture resting, prescribed fire, paddock size and water points – a review. Rangeland Journal, 36(2), 109-130.

View Source

www.publications.qld.gov.au, accessed May 16, 2025,

Contextual Support Journal

The Soils of Cape York Peninsula. Cooktown and Weipa Sections. Land Resource Survey and Evaluation.

View Source

Context

Region Australia
Biome Tropical Monsoonal Savannas
Land Use Production Forestry
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 1 Jun 2026

Notes

Below pH 4.8, soil functions and plant health are severely compromised, marking a critical limit for sustainable production forestry. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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