Soil pH

AUS-TMI-LVG-SPH General Low confidence

Benchmark Value

4.8 pH (CaCl₂)
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.

Evidence & Context

Lower Critical Threshold: pH(CaCl₂) 4.8 Below this level, the ecological integrity of most improved pasture systems is significantly compromised.

Metric Definition:

Soil pH measured in calcium chloride solution (pH(CaCl₂)) representing the lower critical threshold below which aluminium toxicity harms pasture health.

Benchmark Definition:

The pH(CaCl₂) level below which aluminium toxicity causes root damage and pasture degradation in the Tropical & Subtropical Maritime Islands biome.

Justification:

Extensive soil science literature identifies pH(CaCl₂) 4.8 as the tipping point for aluminium toxicity and pasture ecosystem degradation.

Sources (1)

Preview of AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025,
AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025, Journal

VEGETATION 0}' LORD HOWE ISLAND - Botanic Gardens of Sydney

View Source

Context

  • Region Australia
  • Biome Tropical & Subtropical Maritime Islands
  • Land Use Livestock Grazing & Pasture
  • Assessment Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 10 Jun 2026

Notes

Below pH(CaCl₂) 4.8, pasture productivity and microbial activity decline sharply due to toxic aluminium and manganese mobilization. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.