Soil Phosphorus

AUS-TGP-FOR-SOP General High confidence

Benchmark Value

20 mg/kg
Thresholds: Lower: —, Upper: 20
Direction: Lower is desirable ↓
Form: MaximumOnly

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

Evidence & Context

An available soil phosphorus level exceeding 20 mg/kg is considered detrimental to the environmental health and overall ecosystem function of a production forest in this biome.

Metric Definition:

Available soil phosphorus level above which ecological degradation and physiological stress occur.

Benchmark Definition:

Represents a state of ecological degradation and/or physiological stress in temperate grassy woodlands production forestry.

Justification:

Levels above this threshold are associated with direct P toxicity in non-mycorrhizal Eucalyptus species and a systemic shift in the understorey from native-dominated to exotic weed-dominated.

Sources (1)

Preview of Establishment of critical nutrient levels in soil and plant for eucalyptus
Establishment of critical nutrient levels in soil and plant for eucalyptus Journal

Establishment of critical nutrient levels in soil and plant for eucalyptus

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Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

Preview of Phosphorus Nutrition of Proteaceae in Severely Phosphorus-Impoverished Soils: Are There Lessons To Be Learned for Future Crops? - PubMed Central, accessed August 4, 2025
Phosphorus Nutrition of Proteaceae in Severely Phosphorus-Impoverished Soils: Are There Lessons To Be Learned for Future Crops? - PubMed Central, accessed August 4, 2025
Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC

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Preview of Phosphorus uptake and toxicity are delimited by mycorrhizal symbiosis in P-sensitive Eucalyptus marginata but not in P-tolerant Acacia celastrifolia - PubMed Central
Phosphorus uptake and toxicity are delimited by mycorrhizal symbiosis in P-sensitive Eucalyptus marginata but not in P-tolerant Acacia celastrifolia - PubMed Central
Contextual Support Journal

Phosphorus uptake and toxicity are delimited by mycorrhizal symbiosis in P-sensitive Eucalyptus marginata but not in P-tolerant Acacia celastrifolia - PubMed Central

View Source

Context

  • Region Australia
  • Biome Temperate Grassy Woodlands & Plains
  • Land Use Production Forestry
  • Assessment Conservation Target
  • Vegetation Forest
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 24 Mar 2026

Notes

A site with P levels persistently above this threshold cannot be considered to be in a 'best-on-offer' state; it is in a degraded condition.