Fungal:Bacterial Ratio

AUS-TDG-LVG-SFB General Moderate confidence

Benchmark Value

No specific value — see range

Range: 2 to 4 index

Thresholds: Lower: 0.5, Upper: 5

Optimal Range: 2 to 4

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. The scoring engine uses 14 benchmarks together — the OptimalRange form drives the primary score, while 13 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard LowerThreshold Guard UpperThreshold Guard OptimalRange Guard LowerThreshold Guard Point Guard LowerThreshold Guard OptimalRange Guard Point Guard LowerThreshold Guard OptimalRange Guard UpperThreshold Guard Point Guard

Evidence & Context

A target F:B ratio higher than typical "productive agricultural soils" is anticipated. The indication that fungal biomass can be "several times higher than that of bacteria in well managed pastures" suggests that F:B ratios (measured by PLFA or DNA methods) in the range of 2.0 to 4.0 could represent a high-health state for the productive grassland components within the target biome.

Metric Definition:

Fungal:Bacterial ratio (F:B ratio) representing the relative abundance of fungal to bacterial biomass in soil, measured primarily through PLFA or DNA-based quantification methods.

Benchmark Definition:

This benchmark represents the healthy range of fungal to bacterial biomass ratio in soils under regenerative livestock grazing in Australian Temperate Dry Woodlands & Native Grasslands, reflecting improving soil health and productivity.

Justification:

Derived from synthesis of ecological principles, related Australian contexts, and documented outcomes of regenerative agriculture, reflecting reduced disturbance, enhanced soil organic matter, and stable nutrient cycling.

Sources (4)

ausveg - fact sheet: soil microbiology, accessed July 18, 2025 Journal

ausveg - fact sheet: soil microbiology

View Source

Bardgett, R. D., & McAlister, E. (1999). The measurement of soil microbial biomass. Journal of Microbiological Methods, 30(1), 1-16..8 Journal

Bardgett, R. D., & McAlister, E. (1999). The measurement of soil microbial biomass. Journal of Microbiological Methods, 30(1), 1-16..8

View Source

Preview of Biogeographical patterns of the soil fungal:bacterial ratio across France | mSphere, accessed July 28, 2025

Biogeographical patterns of the soil fungal:bacterial ratio across France | mSphere, accessed July 28, 2025 Journal

Mechanisms and implications of bacterial–fungal competition for soil resources - PMC, accessed June 7, 2025,

View Source

Preview of Ingham, E. R. (Various publications and resources, e.g., USDA NCRS Soil Biology Primer, Soil Foodweb Inc. materials)..4

Ingham, E. R. (Various publications and resources, e.g., USDA NCRS Soil Biology Primer, Soil Foodweb Inc. materials)..4 Journal

Are Fungal to Bacterial Ratios (F:B Ratio) Important for Plant Growth? - Garden Myths, accessed July 11, 2025,

View Source

Supporting Sources (7)

Additional references from the underlying research that informed this benchmark.

Analyzing your Fungal to Bacterial Ratio Results - MicroBiometer, accessed July 18, 2025

Contextual Support GreyLiterature

Analyzing your Fungal to Bacterial Ratio Results - microBIOMETER, accessed June 7, 2025,

View Source

Fungal/bacterial ratios in grasslands with contrasting nitrogen management, accessed July 19, 2025,

Contextual Support Journal

Soil Fungal:Bacterial Ratios Are Linked to Altered Carbon Cycling - Frontiers, accessed July 30, 2025,

View Source

Guidelines for grazing in the Gwydir Wetlands and Macquarie Marshes, accessed July 28, 2025,

Contextual Support GreyLiterature

Hamonts, K., Bissett, A., Macdonald, B. C. T., Barton, P. S., Manning, A. D., & Young, A. (2017). Effects of ecological restoration on soil microbial diversity in a temperate grassy woodland. Applied Soil Ecology, 117-118, 117-128. 10 (Note: The specific F:B data was not available from the abstract, but the study is highly relevant for context).

View Source

Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based ..., accessed August 5, 2025,

Contextual Support Journal

Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based Pastures in Southern Australia | PLOS One - Research journals

View Source

Living soils in agriculture | TERN Australia, accessed July 25, 2025,

Contextual Support Government

Living soils in agriculture | TERN Australia, accessed July 16, 2025,

View Source

Role of Soil Fungus | Ohioline - The Ohio State University, accessed on June 5, 2025

Contextual Support GreyLiterature

The fungal-bacterial ratio for soil health - Farmer's Weekly, accessed June 7, 2025,

View Source

Tagged with ratio of fungi to bacteria - The Prairie Ecologist, accessed July 28, 2025

Contextual Support GreyLiterature

Analyzing your Fungal to Bacterial Ratio Results - microBIOMETER, accessed July 21, 2025

View Source

Context

Region Australia
Biome Temperate Dry Woodlands & Native Grasslands
Land Use Livestock Grazing & Pasture
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Lower Critical Threshold: 0.5 index. Optimal Range (suggested): 1.0 – 4.0 index. Upper Detrimental Threshold: 5 index. Ratios significantly above 5 may indicate undesirable woody encroachment reducing grazing utility. [Migration] Original wider evidence range: 1 – 4 (retained OptimalRange: 2 – 4)

Related Benchmarks

Other benchmarks in the AUS-TDG-LVG-SFB family.