Soil Potassium

AUS-TSR-CON-SOK General Moderate confidence

Benchmark Value

120 mg/kg

Thresholds: Lower: 120, Upper: —

Direction: Higher 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.

Evidence & Context

A threshold of <120 mg/kg should be applied to clay-rich soils.

Metric Definition:

Colwell K value representing plant-available potassium in soil

Benchmark Definition:

This benchmark represents the maximum Colwell K value threshold below which clay-rich soils are considered to be at risk of potassium deficiency in tropical and subtropical rainforest conservation areas.

Justification:

Agronomic guides classify Colwell K levels of less than 110–120 mg/kg as 'Low' for clay loams and clays.

Sources (1)

Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025 Government

Understanding soil tests for pastures

View Source

Supporting Sources (3)

Additional references from the underlying research that informed this benchmark.

Potassium | Fact Sheets | soilquality.org.au

Direct Evidence Government

Potassium | Fact Sheets | soilquality.org.au

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Rainforest – Processes (Department of the Environment, Tourism ..., accessed July 20, 2025,

Direct Evidence Government

Nutrient distribution and cycling in a subtropical rainforest in New South Wales

View Source

TROPICAL SOILS | Terrain NRM, accessed July 16, 2025,

Direct Evidence Journal

Water Retention - Oz Soils 4 - UNE, accessed May 11, 2025,

View Source

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Below this concentration, core ecosystem functions are likely compromised.

Related Benchmarks

Other benchmarks in the AUS-TSR-CON-SOK family.