Soil Potassium
Benchmark Value
Scoring Curve
This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.
Evidence & Context
Agriculture Victoria guidelines suggest that if exchangeable potassium exceeds 10% of the soil's CEC, it may lead to magnesium deficiency in plants and animals. The 'High' Colwell K categories provided by Agriculture Victoria serve as a practical upper boundary beyond which K inputs are generally considered unnecessary and could be reduced: Sands: > 150 mg/kg, Sandy Loams: > 200 mg/kg, Clay Loams: > 250 mg/kg, Clays: > 300 mg/kg.
Upper detrimental threshold for soil potassium (Colwell K) based on nutrient imbalance risk
This benchmark defines the upper detrimental soil potassium threshold where nutrient imbalances, especially magnesium deficiency, may occur in the target biome's agricultural soils.
Exceeding these levels may lead to magnesium deficiency in plants and animals, and K inputs beyond these thresholds are generally unnecessary and could be reduced.
Sources (1)
Understanding soil tests for pastures
View SourceSupporting Sources (4)
Additional references from the underlying research that informed this benchmark.
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 SourceSoil fertility in grazing systems: Manage potassium to manage nitrogen - Crops and Soils, accessed July 28, 2025,
View Source
Regenerative agriculture – Case studies from Western Australia, accessed May 10, 2025
View SourceScanlan, C. A., et al. (2013). Soil Quality: 10 Plant Nutrition. CCMA Soil Health Knowledge Base.
View Source