Soil Potassium

AUS-TGP-AGR-SOK General Moderate confidence

Benchmark Value

50 mg/kg
Thresholds: Lower: 50, Upper: —
Direction: Higher is desirable ↑
Form: LowerThreshold

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 15 benchmarks together — the OptimalRange form drives the primary score, while 14 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary OptimalRange Guard MinimumOnly Guard MaximumOnly Guard MaximumOnly Guard Point Guard Point Guard LowerThreshold Guard OptimalRange Guard Point Guard OptimalRange Guard MinimumOnly Guard OptimalRange Guard LowerThreshold Guard OptimalRange Guard

Evidence & Context

A critical deficiency level of < 50 mg/kg (Colwell-K) is widely cited as the point where a response to fertiliser is likely.

Metric Definition:

Critical deficiency level of Colwell-K in 0–10 cm topsoil

Benchmark Definition:

Critical deficiency level below which potassium deficiency compromises plant health and system resilience.

Justification:

Based on achieving 90% of potential yield and widely cited by Australian agricultural research bodies.

Sources (1)

Preview of Potassium and sulphur - emerging deficiencies in the southern region - GRDC, accessed July 13, 2025
Potassium and sulphur - emerging deficiencies in the southern region - GRDC, accessed July 13, 2025 Government

Potassium and sulphur - emerging deficiencies in the southern region - GRDC

View Source

Supporting Sources (25)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Determining reference conditions for management and ..., accessed August 5, 2025,
(PDF) Determining reference conditions for management and ..., accessed August 5, 2025,
Contextual Support

(PDF) Impacts of tree invasion on floristic composition of subtropical grasslands on the Bunya Mountains, Australia - ResearchGate, accessed May 19, 2025

View Source
Preview of (PDF) Identifying ecological barriers to restoration in temperate ...
(PDF) Identifying ecological barriers to restoration in temperate ...
Contextual Support Journal

(PDF) Identifying ecological barriers to restoration in temperate ...

View Source
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,
Contextual Support Journal

The Western Australian Rangeland Monitoring System (WARMS) – operating a regional scale monitoring system - ResearchGate, accessed July 24, 2025

View Source
Preview of Australia state of the environment 2021: land
Australia state of the environment 2021: land
Contextual Support Journal

A state-and-transition model to guide grassland management - CSIRO Publishing

View Source
Preview of Australia state of the environment 2021: land, accessed May 11, 2025
Australia state of the environment 2021: land, accessed May 11, 2025
Contextual Support Journal

Management Standards and Procedures for timber harvesting operations in Victoria’s State forests

View Source
Preview of Chapter 9 AUSTRALIAN GRASSLANDS - Food and Agriculture Organization of the United Nations, accessed August 5, 2025,
Chapter 9 AUSTRALIAN GRASSLANDS - Food and Agriculture Organization of the United Nations, accessed August 5, 2025,
Contextual Support Government

Karst and agriculture in Australia - Digital Commons @ USF, accessed July 26, 2025,

View Source
Preview of Comparison of soil analytical methods for estimating plant-available potassium in highly weathered soils - CSIRO Publishing
Comparison of soil analytical methods for estimating plant-available potassium in highly weathered soils - CSIRO Publishing
Contextual Support Journal

Crop and Pasture Science - CSIRO PUBLISHING

View Source
Preview of Fertilization and Soil Microbial Community: A Review - MDPI
Fertilization and Soil Microbial Community: A Review - MDPI
Contextual Support Journal

Fertilization and Soil Microbial Community: A Review - MDPI

View Source
Preview of How do fire regimes affect ecosystem structure, function and diversity in grasslands and grassy woodlands of southern Australia?, accessed August 10, 2025,
How do fire regimes affect ecosystem structure, function and diversity in grasslands and grassy woodlands of southern Australia?, accessed August 10, 2025,
Contextual Support

Soil | Australia state of the environment 2021

View Source
Preview of Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,
Contextual Support Journal

(PDF) Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 4, 2025,

View Source
Preview of Managing potassium nutrition in cereals and canola for this season - GRDC
Managing potassium nutrition in cereals and canola for this season - GRDC
Contextual Support GreyLiterature

Managing potassium nutrition in cereals and canola for this season - GRDC

View Source
Preview of Microbial activity and carbon rates the soil in response to the application of potassium sources - Redalyc
Microbial activity and carbon rates the soil in response to the application of potassium sources - Redalyc
Contextual Support Journal

Microbial activity and carbon rates the soil in response to the application of potassium sources - Redalyc

View Source
Preview of Plant nutrients in the soil - NSW Department of Primary Industries
Plant nutrients in the soil - NSW Department of Primary Industries
Contextual Support GreyLiterature

Plant nutrients in the soil - NSW Department of Primary Industries

View Source
Preview of Plant nutrients in the soil - NSW Department of Primary Industries, accessed July 18, 2025,
Plant nutrients in the soil - NSW Department of Primary Industries, accessed July 18, 2025,
Contextual Support Government

Rangelands Living Skin | .Meat & Livestock Australia - MLA, accessed July 28, 2025,

View Source
Preview of Potassium | Fact Sheets | soilquality.org.au, accessed August 11, 2025,
Potassium | Fact Sheets | soilquality.org.au, accessed August 11, 2025,
Contextual Support Government

Soil fertility in grazing systems: Manage potassium to manage nitrogen - Crops and Soils, accessed July 28, 2025,

View Source
Preview of Potassium Control of Plant Functions: Ecological and Agricultural Implications - MDPI, accessed August 11, 2025,
Potassium Control of Plant Functions: Ecological and Agricultural Implications - MDPI, accessed August 11, 2025,
Contextual Support Journal

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

View Source
Preview of Potassium Control of Plant Functions: Ecological and Agricultural Implications - PMC, accessed May 28, 2025,
Potassium Control of Plant Functions: Ecological and Agricultural Implications - PMC, accessed May 28, 2025,
Contextual Support GreyLiterature

Soil tests get K levels right - Agronomic Insights

View Source
Preview of Potassium Uptake and Ohio Crop Response | Ohioline
Potassium Uptake and Ohio Crop Response | Ohioline
Contextual Support Government

Potassium Uptake and Ohio Crop Response | Ohioline

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Preview of Regenerative Agriculture - Landscape SA, accessed July 6, 2025,
Regenerative Agriculture - Landscape SA, accessed July 6, 2025,
Contextual Support Government

Regenerative Agriculture - Local Land Services

View Source
Preview of Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 5, 2025,
Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 5, 2025,
Direct Evidence Journal

Regenerative Agriculture—A Literature Review on the Practices and Mechanisms Used to Improve Soil Health - MDPI, accessed August 28, 2025,

View Source
Preview of SciELO Brasil - Potassium chloride: impacts on soil microbial activity ...
SciELO Brasil - Potassium chloride: impacts on soil microbial activity ...
Contextual Support Journal

Potassium chloride: impacts on soil microbial activity and nitrogen mineralization - SciELO, accessed July 28, 2025,

View Source
Preview of Soil health stocktake Queensland - GRDC, accessed May 11, 2025,
Soil health stocktake Queensland - GRDC, accessed May 11, 2025,
Contextual Support Government

Soil health stocktake Queensland - GRDC, accessed July 28, 2025,

View Source
Preview of Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,
Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,
Contextual Support GreyLiterature

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 17, 2025,

View Source
Preview of Under the radar: Potassium on loamy soil - SoilsWest
Under the radar: Potassium on loamy soil - SoilsWest
Contextual Support GreyLiterature

Under the radar: Potassium on loamy soil - SoilsWest

View Source
Preview of Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025
Understanding soil tests for pastures | Soil | Farm management ..., accessed May 12, 2025
Direct Evidence Government

Understanding soil tests for pastures

View Source

Context

  • Region Australia
  • Biome Temperate Grassy Woodlands & Plains
  • Land Use Agricultural Crop Production
  • Assessment Pristine Reference
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Superseded
  • Version 1
  • Effective From 24 Mar 2026
  • Effective To 25 Mar 2026

Notes

Texture-dependent thresholds vary; legumes require higher levels (<80 mg/kg).

Related Benchmarks

Other benchmarks in the AUS-TGP-AGR-SOK family.

— mg/kg High
Agricultural Crop Production · Pristine Reference
OptimalRange Active v2
50 mg/kg Moderate
Agricultural Crop Production · Pristine Reference
LowerThreshold Active v2
— mg/kg High
Agricultural Crop Production · Conservation Target
OptimalRange Active v1
— mg/kg High
Agricultural Crop Production · Conservation Target
OptimalRange Active v1
— mg/kg High
Agricultural Crop Production · Conservation Target
OptimalRange Active v1
— mg/kg High
Agricultural Crop Production · Conservation Target
OptimalRange Active v1
— mg/kg High
Agricultural Crop Production · Pristine Reference
OptimalRange Superseded v1