Soil Potassium

AUS-AIF-CON-SOK General Moderate confidence

Benchmark Value

No specific value — see range

Range: 150 to 300 mg/kg

Optimal Range: 150 to 300

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

Synthesizing this evidence, a benchmark representing the best available condition for clay-rich soils (Vertosols and similar alluvial clays) in arid floodplain conservation areas can be established. A value that is clearly above the deficiency thresholds for other systems and sits comfortably within the range observed in naturally fertile, non-responsive soils is appropriate. Therefore, a benchmark range of 150 - 300 mg/kg (Colwell K) is proposed.

Metric Definition:

Available soil potassium measured as Colwell K, representing plant-available potassium in soil.

Benchmark Definition:

Benchmark range for available soil potassium in clay-rich floodplain soils representing the best available natural condition.

Justification:

Derived from non-responsive agricultural trials on similar clay soils where baseline Colwell K values were consistently above 120 mg/kg, indicating natural potassium sufficiency for ecological function.

Sources (2)

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, Journal

Nutrient Cycling in Australian Savannas on JSTOR - DOI

View Source

Availability of soil potassium and diagnostic soil tests - DPI eResearch Archive (eRA) Journal

Availability of soil potassium and diagnostic soil tests - DPI eResearch Archive (eRA)

View Source

Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

Soil potassium—crop response calibration relationships and criteria for field crops grown in Australia

Direct Evidence

Soil potassium—crop response calibration relationships and criteria for field crops grown in Australia

View Source

Context

Region Australia
Biome Arid Inland Floodplains & Ephemeral River Systems
Land Use Conservation / Protected Natural Areas
Assessment Conservation Target
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

Lower Critical Threshold: 100 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. No upper detrimental threshold identified; upper boundary is natural saturation. Lower critical threshold is <100 mg/kg indicating potential ecosystem stress.

Related Benchmarks

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