Microbial Biomass Carbon (MBC)

AUS-TGP-AGR-SMB General Moderate confidence

Benchmark Value

191 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. 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

This benchmark is derived from a long-term (17-year) trial at Merredin, WA, under no-till with full stubble retention, representing a key best practice for continuous cropping. The original value of 229 kg C/ha (0-10 cm) was converted to ~191 mg/kg using a standard bulk density of 1.2 g/cm³.

Metric Definition:

Microbial Biomass Carbon (MBC) represents the total mass of living microorganisms within the soil matrix.

Benchmark Definition:

Microbial Biomass Carbon (MBC) is the living, dynamic engine driving biogeochemical processes in soil within temperate grassy woodlands under agricultural crop production.

Justification:

The value is based on a robust, peer-reviewed long-term trial relevant to the temperate Australian cropping biome.

Sources (4)

Altered soil microbial community at elevated CO2 leads to loss of soil carbon | PNAS, accessed August 5, 2025

Altered soil microbial community at elevated CO2 leads to loss of soil carbon | PNAS

View Source

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au, accessed August 28, 2025, GreyLiterature

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au

View Source

Preview of Microbial Biomass Carbon - NSW | Fact Sheets | soilquality.org.au, accessed August 5, 2025,

Microbial Biomass Carbon - NSW | Fact Sheets | soilquality.org.au, accessed August 5, 2025, GreyLiterature

www.soilquality.org.au

View Source

Preview of Procedure for Soil Respiration (CO2 Evolution from Rewetting a Dried Soil) - Soil Fertility, accessed July 9, 2025

Procedure for Soil Respiration (CO2 Evolution from Rewetting a Dried Soil) - Soil Fertility, accessed July 9, 2025 GreyLiterature

Tool 6.7 Soil health benchmarks and guidelines for managing ...

View Source

Supporting Sources (5)

Additional references from the underlying research that informed this benchmark.

Soil Carbon Sequestration Potential: A review for Australian agriculture - MLA

Contextual Support Journal

Soil Carbon Sequestration Potential: A review for Australian agriculture - MLA

View Source

Soil microbial biomass carbon (SMBC) under different cropping systems... - ResearchGate

Contextual Support Journal

Soil microbial biomass carbon (SMBC) under different cropping systems... - ResearchGate

View Source

Soil microbial biomass—what do the numbers really mean? - ResearchGate, accessed August 28, 2025,

Direct Evidence GreyLiterature

Responses of soil labile organic carbon stocks and the carbon pool management index to different vegetation restoration types in the Danxia landform region of southwest China - PMC - PubMed Central

View Source

Soil microbial biomass, activity and nutrient cycling as indicators of soil health.

Contextual Support GreyLiterature

Soil microbial biomass, activity and nutrient cycling as indicators of soil health., accessed August 5, 2025

View Source

Soil organic carbon thresholds control fertilizer effects on carbon accrual in croplands worldwide - PMC

Contextual Support Journal

Soil organic carbon thresholds control fertilizer effects on carbon accrual in croplands worldwide - PMC

View Source

Context

Region Australia
Biome Temperate Grassy Woodlands & Plains
Land Use Agricultural Crop Production
Assessment Not Stated
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 4 Jun 2026

Notes

This value represents the best available condition for continuous cropping with no-till and stubble retention, not the maximum potential achievable with perennial systems. No upper detrimental threshold — higher values are always better up to natural saturation. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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