Soil Potassium

AUS-TMI-AGR-SOK General Moderate confidence

Benchmark Value

220 mg/kg

Direction: Higher is desirable ↑

Form: Point

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.

Contributing Benchmarks

OptimalRange Primary Point Guard MinimumOnly Guard

Evidence & Context

The benchmark is derived via synthesis, as no direct studies exist for this specific biome/land use. It is anchored by the critical value of 224 mg/kg (rounded to 220 mg/kg) identified for high-yield potato cropping in analogous volcanic Andisols, which aligns with the upper end of optimal ranges (150-300 mg/kg) observed in high-rainfall Australian systems.

Metric Definition:

Available soil potassium (Colwell K test)

Benchmark Definition:

This benchmark represents the critical soil potassium level for healthy and productive agricultural crop production in the Tropical & Subtropical Maritime Islands biome, based on synthesis from analogous volcanic soils and high-rainfall Australian systems. It indicates a state of nutrient sufficiency and ecological function for loamy to clay-loam soils.

Justification:

The benchmark is derived via synthesis from multiple relevant data domains including high-productivity Australian systems and international volcanic soil analogues, providing a robust foundation despite the absence of direct measurements in the target biome.

Sources (4)

Adequate Nutrient Levels in Soils and Plants in Hawaii - ResearchGate Journal

Adequate Nutrient Levels in Soils and Plants in Hawaii - ResearchGate

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Critical Value of Soil Potassium for Potato Crops in Volcanic Soils | Request PDF Journal

Critical Value of Soil Potassium for Potato Crops in Volcanic Soils | Request PDF

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Potassium | Fact Sheets | soilquality.org.au, accessed August 11, 2025, Government

Potassium | Fact Sheets | soilquality.org.au

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Preview of Potassium for high-performing pastures | Nutrient Advantage, accessed July 18, 2025,

Potassium for high-performing pastures | Nutrient Advantage, accessed July 18, 2025, Journal

Potassium for high rainfall pastures - DPIRD's Digital library

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

Critical Value of Soil Potassium for Potato Crops in Volcanic Soils

Contextual Support Journal

Critical Value of Soil Potassium for Potato Crops in Volcanic Soils

View Source

Preview of Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - CSIRO PUBLISHING | Crop and Pasture Science

Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - CSIRO PUBLISHING | Crop and Pasture Science

Contextual Support Government

Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - CSIRO PUBLISHING | Crop and Pasture Science

View Source

Norfolk Island Water Resource Assessment - CSIRO

Contextual Support Government

Norfolk Island Water Resource Assessment - CSIRO

View Source

Potassium's pivotal role - Agronomic Insights

Contextual Support Journal

Potassium's pivotal role - Agronomic Insights

View Source

Context

Region Australia
Biome Tropical & Subtropical Maritime Islands
Land Use Agricultural Crop Production
Assessment Agricultural Biodiversity Target
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Lower Critical Threshold: Below 80-100 mg/kg (Colwell K), ecological function is compromised based on pasture legume requirements. Optimal Range: 150-250 mg/kg is considered optimal for ecologically healthy and productive systems on loamy to clay-loam soils. Upper Detrimental Threshold: No fixed concentration; risk arises when exchangeable potassium exceeds 10% of soil CEC or Mg:K ratio falls below 1.5:1, indicating cation imbalance.