Microbial Biomass Carbon (MBC)

AUS-AIF-AGR-SMB General Moderate confidence

Benchmark Value

350 mg/kg
Direction: Higher is desirable ↑
Form: MinimumOnly

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

Contributing Benchmarks

OptimalRange Primary Point Guard MinimumOnly Guard OptimalRange Guard Point Guard MinimumOnly Guard Point Guard MinimumOnly Guard OptimalRange Guard Point Guard MinimumOnly Guard OptimalRange Guard Point Guard MinimumOnly Guard OptimalRange Guard MinimumOnly Guard

Evidence & Context

A lower critical threshold of ~350 mg/kg is proposed for the target agro-ecosystem. MBC levels below this value are indicative of a soil in a state of significant biological decline, where essential ecosystem services are impaired.

Metric Definition:

Lower critical threshold below which soil biological function is significantly impaired

Benchmark Definition:

This benchmark defines the minimum Microbial Biomass Carbon level below which soil biological function is significantly impaired in agricultural cropping systems in Australia's Arid Inland Floodplains.

Justification:

The threshold is based on convergent data from degraded Australian cropping systems and international functional studies, including a Brazilian study linking microbial indicators to crop yield.

Sources (1)

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

Interpretation of Microbial Indicators As a Function of Crop Yield and Organic Carbon In Cerrado Soils. | Request PDF - ResearchGate

View Source

Supporting Sources (17)

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 Government

An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river - Frontiers, accessed July 20, 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
Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group
Contextual Support GreyLiterature

Availability of N from cereal stubble: 15N trial summary 2014-2016 | Birchip Cropping Group

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

Impact of forest vegetation on soil characteristics: a correlation between soil biological and physico-chemical properties - PMC

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 Government

Soil and Landscape Grid of Australia - CSIRO

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 ...
Contextual Support 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 ...
Contextual Support Government

Bell et al. (GRDC) 26

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 Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 3 Jun 2026

Notes

Below this level, the soil's resilience is compromised, productivity declines, and the risk of further degradation increases significantly. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-AIF-AGR-SMB family.

— mg/kg Moderate
Agricultural Crop Production · Not Stated
OptimalRange Active v2
— mg/kg Low
Agricultural Crop Production · Not Stated
OptimalRange Superseded v1