Soil Potassium

AUS-AKW-AGR-SOK General Moderate confidence

Benchmark Value

300 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 4 benchmarks together — the OptimalRange form drives the primary score, while 3 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard MaximumOnly Guard Point Guard

Evidence & Context

A value of 300 mg/kg serves as a practical and conservative benchmark, situated within the optimal range and representative of the non-responsive trial sites.

Metric Definition:

Colwell K soil test concentration representing plant-available potassium in soil.

Benchmark Definition:

This benchmark represents a high natural capital state of soil potassium in arid karstic cropping systems, indicating sufficient native potassium supply for crop demand without yield response to fertiliser.

Justification:

Based on multi-site field trials showing Calcarosols with Colwell K >280 mg/kg are non-responsive to K fertiliser, indicating a K-replete, non-degraded system.

Sources (1)

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

Supporting Sources (3)

Additional references from the underlying research that informed this benchmark.

Preview of Calcareous Soils Initiative - GRDC, accessed July 22, 2025,
Calcareous Soils Initiative - GRDC, accessed July 22, 2025,
Contextual Support Government

Some Characteristics of Calcareous soils. A review A.S. Taalab1, G.W. Ageeb2, Hanan S. Siam1 and Safaa A. Mahmoud1 - CURRENT RESEARCH WEB

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 - BioOne Complete, accessed July 10, 2025
Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - BioOne Complete, accessed July 10, 2025
Contextual Support Journal

Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review - BioOne Complete

View Source
Preview of Potassium Control of Plant Functions: Ecological and Agricultural Implications - PMC
Potassium Control of Plant Functions: Ecological and Agricultural Implications - PMC
Contextual Support Journal

Potassium Control of Plant Functions: Ecological and Agricultural Implications - PMC

View Source

Context

  • Region Australia
  • Biome Arid Karstic Woodlands & Shrublands
  • Land Use Agricultural Crop Production
  • Assessment Not Stated
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 10 Jun 2026

Notes

Lower Critical Threshold: ~50-80 mg/kg below which ecological resilience is compromised. Optimal Range: 80-300 mg/kg representing a healthy system conserving its native K. Upper Detrimental Threshold: No absolute toxicity limit exists; levels >300 mg/kg, especially from fertiliser, risk cation imbalances. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.