Microbial Biomass Carbon (MBC)

AUS-AIF-AGR-SMB General Moderate confidence

Benchmark Value

No specific value — see range
Range: 670 to 790 mg/kg
Thresholds: Lower: 350, Upper: —
Optimal Range: 670 to 790
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 7 benchmarks together — the OptimalRange form drives the primary score, while 6 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

The final benchmark, functional thresholds, and confidence level are presented in Table 1.

Metric Definition:

Microbial Biomass Carbon (MBC) representing a state of high ecological health for agricultural crop production within Australia's Arid Inland Floodplains and Ephemeral River Systems.

Benchmark Definition:

Microbial Biomass Carbon (MBC) indicates soil ecological health in agricultural crop production on arid inland floodplains, with optimal levels reflecting high-health conditions achievable through regenerative practices.

Justification:

The benchmark range is derived from a best-practice, stubble-retained cropping system on a Vertisol soil in a semi-arid Australian environment, representing a high-health condition achievable under regenerative management. The lower critical threshold is based on convergent data from degraded Australian cropping systems and international functional studies. Literature does not support a detrimental upper threshold for MBC built via in-situ regenerative practices.

Sources (4)

Preview of Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group
Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group
View Source
Preview of Interpretation of Microbial Indicators As a Function of Crop Yield and Organic Carbon In Cerrado Soils. | Request PDF - ResearchGate
Interpretation of Microbial Indicators As a Function of Crop Yield and Organic Carbon In Cerrado Soils. | Request PDF - ResearchGate Journal

Management practices to reduce losses or increase soil carbon stocks in temperate grazed grasslands: New Zealand as a case study - ResearchGate, accessed July 17, 2025

View Source
Preview of Soil carbon and nitrogen dynamics in a Vertisol following 50 years of ...
Soil carbon and nitrogen dynamics in a Vertisol following 50 years of ... Journal

The nitrogen book: Principles of soil nitrogen fertility management in southern Queensland and northern New South Wales farming, accessed August 4, 2025,

View Source
Preview of Stubble and nutrient management to build soil carbon – challenges ...
Stubble and nutrient management to build soil carbon – challenges ... Government

Stubble and nutrient management to build soil carbon – challenges and opportunities - Grains Research and Development Corporation (GRDC), accessed July 17, 2025

View Source

Supporting Sources (14)

Additional references from the underlying research that informed this benchmark.

Preview of An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 17, 2025
An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 17, 2025
Contextual Support Government

An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 17, 2025

View Source
Preview of An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 20, 2025
An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 20, 2025
Contextual Support Journal

Connectivity – New South Wales Irrigators' Council, accessed July 17, 2025

View Source
Preview of Assessing Groundwater Connection/Disconnection to Waterholes Along the Balonne River and in the Barwon–Darling River System in Queensland and New South Wales, Australia, for Waterhole Persistence - MDPI, accessed July 17, 2025
Assessing Groundwater Connection/Disconnection to Waterholes Along the Balonne River and in the Barwon–Darling River System in Queensland and New South Wales, Australia, for Waterhole Persistence - MDPI, accessed July 17, 2025
Contextual Support Journal

Assessing Groundwater Connection/Disconnection to Waterholes Along the Balonne River and in the Barwon–Darling River System in Queensland and New South Wales, Australia, for Waterhole Persistence - MDPI, accessed July 17, 2025

View Source
Preview of Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group, accessed July 17, 2025
Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group, accessed July 17, 2025
Direct Evidence Journal

Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group, accessed July 17, 2025

View Source
Preview of CHAPTER 9 Ephemeral and endoreic river systems: Relevance and management challenges - Anthony Turton, accessed July 17, 2025
CHAPTER 9 Ephemeral and endoreic river systems: Relevance and management challenges - Anthony Turton, accessed July 17, 2025
Contextual Support Journal

CHAPTER 9 Ephemeral and endoreic river systems: Relevance and management challenges - Anthony Turton, accessed July 17, 2025

View Source
Preview of Climate-Smart Agricultural Practices—Strategies to Conserve and Increase Soil Carbon in Hungary - MDPI, accessed July 17, 2025
Climate-Smart Agricultural Practices—Strategies to Conserve and Increase Soil Carbon in Hungary - MDPI, accessed July 17, 2025
Contextual Support Journal

Climate-Smart Agricultural Practices—Strategies to Conserve and Increase Soil Carbon in Hungary - MDPI, accessed July 17, 2025

View Source
Preview of Effect of strategic tillage in soil microbial communities in Vertisols from Queensland, Australia - UQ eSpace, accessed July 17, 2025
Effect of strategic tillage in soil microbial communities in Vertisols from Queensland, Australia - UQ eSpace, accessed July 17, 2025
Contextual Support Journal

Effect of strategic tillage in soil microbial communities in Vertisols from Queensland, Australia - UQ eSpace, accessed July 21, 2025

View Source
Preview of Examining links between soil management, soil health, and public benefits in agricultural landscapes: An Australian perspective | Request PDF - ResearchGate, accessed August 10, 2025,
Examining links between soil management, soil health, and public benefits in agricultural landscapes: An Australian perspective | Request PDF - ResearchGate, accessed August 10, 2025,
Contextual Support Journal

Soil condition | NSW State of the Environment, accessed July 27, 2025,

View Source
Preview of functions-of-soil-organic-matter-and-the-effect-on-soil-properties.pdf.pdf, accessed July 17, 2025
functions-of-soil-organic-matter-and-the-effect-on-soil-properties.pdf.pdf, accessed July 17, 2025
Contextual Support

functions-of-soil-organic-matter-and-the-effect-on-soil-properties.pdf.pdf, accessed July 17, 2025

View Source
Preview of functions-of-soil-organic-matter-and-the-effect-on-soil-properties.pdf.pdf, accessed July 19, 2025,
functions-of-soil-organic-matter-and-the-effect-on-soil-properties.pdf.pdf, accessed July 19, 2025,
Contextual Support Journal

The biodiversity cost of carbon sequestration in tropical savanna - PMC - PubMed Central

View Source
Preview of Human-induced land use changes and phosphorus limitation affect soil microbial biomass and ecosystem stoichiometry | PLOS One, accessed July 17, 2025
Human-induced land use changes and phosphorus limitation affect soil microbial biomass and ecosystem stoichiometry | PLOS One, accessed July 17, 2025
Contextual Support Journal

Human-induced land use changes and phosphorus limitation affect soil microbial biomass and ecosystem stoichiometry | PLOS One, accessed July 17, 2025

View Source
Preview of Soil and Landscape Grid of Australia - CSIRO, accessed July 30, 2025,
Soil and Landscape Grid of Australia - CSIRO, accessed July 30, 2025,
Contextual Support

Soil and Landscape Grid of Australia - CSIRO, accessed August 1, 2025

View Source
Preview of THE EFFECTS OF SALINITY AND SODICITY ON SOIL ORGANIC CARBON STOCKS AND FLUXES - Open Research Repository, accessed July 17, 2025
THE EFFECTS OF SALINITY AND SODICITY ON SOIL ORGANIC CARBON STOCKS AND FLUXES - Open Research Repository, accessed July 17, 2025
Contextual Support Journal

Relationships between soil organic matter and the soil microbial biomass (size, functional diversity, and community structure) in crop and pasture systems in a semi-arid environment - CSIRO Publishing, accessed July 17, 2025

View Source
Preview of The short-term cover crops increase soil labile organic carbon in southeastern Australia, accessed July 17, 2025
The short-term cover crops increase soil labile organic carbon in southeastern Australia, accessed July 17, 2025
Contextual Support Journal

(PDF) Assessing the effect of crop residue removal on soil organic carbon storage and microbial activity in a no-till cropping system - ResearchGate

View Source

Context

  • Region Australia
  • Biome Arid Inland Floodplains & Ephemeral River Systems
  • Land Use Agricultural Crop Production
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 18 Mar 2026

Notes

Lower Critical Threshold: 350 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The optimal range for ecological health and sustainable production is 400–800 mg/kg. RangeFixup applied 2026-03-21 22:21 UTC: LowerBound: 670 → 400; OptimalRangeLow: 400 → 670; OptimalRangeHigh: 800 → 790; UpperBound: 790 → 800 [Migration] Original wider evidence range: 400 – 800 (retained OptimalRange: 670 – 790)