Microbial Biomass Carbon (MBC)

AUS-TDG-AGR-SMB General Moderate confidence

Benchmark Value

557 mg/kg
Direction: Higher is desirable ↑
Form: Point

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.

Evidence & Context

At a site in Tintinara, South Australia, characterized by a Sodosol (a common soil type in some temperate dryland regions), the control plots in an agricultural system exhibited an MBC of 557 mg C/kg soil in the 0-10 cm depth, with a corresponding SOC of 1.8%.

Metric Definition:

Microbial Biomass Carbon (MBC) is defined as the total carbon contained within the living cells of microorganisms in the soil, primarily bacteria, fungi, and archaea, expressed as milligrams of carbon per kilogram of dry soil (mg C/kg soil).

Benchmark Definition:

Reference benchmark for MBC in the topsoil (0-10 cm) representing best available condition under best-practice sustainable or regenerative agricultural crop production in Australia's Temperate Dry Woodlands & Native Grasslands biome.

Justification:

This value is a robust, measured value from a relevant Australian agricultural system and soil type within the target biome, representing a high observed MBC in a relevant temperate dryland context.

Sources (2)

Preview of Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field
Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field Journal

The Long-Term Effect of Biochar on Soil Microbial Abundance, Activity and Community Structure Is Overwritten by Land Management - Frontiers

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Preview of Regenerative opportunities for building soil biological resilience – a ..., accessed May 11, 2025
Regenerative opportunities for building soil biological resilience – a ..., accessed May 11, 2025 GreyLiterature

Soil and fertilizer phosphorus: Effects on plant P supply and mycorrhizal development - Canadian Science Publishing, accessed August 28, 2025

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Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

Preview of Farming systems can affect soil biology, soil pathogens and system ...
Farming systems can affect soil biology, soil pathogens and system ...
Contextual Support Journal

Farming system impact on soil biology and functions

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Context

  • Region Australia
  • Biome Temperate Dry Woodlands & Native Grasslands
  • Land Use Agricultural Crop Production
  • Assessment Conservation Target
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 17 Mar 2026

Notes

Supported by average MBC of 338 mg/kg in 35 low-rainfall cropping fields under conservation practices. No evidence found for an upper detrimental threshold; more MBC generally better up to natural limits.