Soil Potassium

AUS-TCF-AGR-SOK General Moderate confidence

Benchmark Value

No specific value — see range

Range: 80 to 150 mg/kg

Optimal Range: 80 to 150

Direction: Higher is desirable ↑

Form: OptimalRange

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.

Evidence & Context

For broadacre cropping systems, including crops like wheat, barley, canola, oats, and pulses, grown on loamy soils that are commonly found in parts of this biome, a target Colwell K range of 80-150 mg/kg appears to be a reasonable starting point.

Metric Definition:

Soil Potassium (Colwell K)

Benchmark Definition:

This benchmark represents the target range of bicarbonate-extractable soil potassium (Colwell K) for broadacre cropping systems on loamy soils in the Temperate Coastal Forests & Woodlands biome, aimed at supporting optimal crop yield.

Justification:

Informed by ideal levels suggested for pastures on loamy soils in Victoria and general critical values for broadacre crops in WA and SA.

Sources (1)

Preview of Potassium | Fact Sheets | soilquality.org.au, accessed July 10, 2025

Potassium | Fact Sheets | soilquality.org.au, accessed July 10, 2025 Government

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - CSIRO Publishing, accessed July 17, 2025

View Source

Supporting Sources (5)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Soil potassium—crop response calibration relationships and criteria for field crops grown in Australia - ResearchGate, accessed July 18, 2025,

(PDF) Soil potassium—crop response calibration relationships and criteria for field crops grown in Australia - ResearchGate, accessed July 18, 2025,

Direct Evidence Journal

Nutrient Cycling in Australian Savannas on JSTOR - DOI

View Source

Crop and Pasture Science - CSIRO PUBLISHING, accessed July 10, 2025

Direct Evidence Journal

Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - CSIRO Publishing, accessed July 17, 2025

View Source