Microbial Biomass Carbon (MBC)

AUS-TSR-AGR-SMB General Moderate confidence

Benchmark Value

200 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.

Evidence & Context

Based on the available evidence, an MBC level below 200 mg/kg in this biome should be considered indicative of a degraded state.

Metric Definition:

Microbial Biomass Carbon (MBC) level below which soil function is significantly compromised.

Benchmark Definition:

This benchmark defines a lower critical threshold for microbial biomass carbon below which soil function is considered degraded in tropical and subtropical rainforest agricultural crop production.

Justification:

The long-term conventional sugarcane sites in North Queensland, with MBC around 185 mg/kg, already exhibit clear signs of microbial stress and functional inefficiency.

Sources (1)

Preview of Sugarcane cultivation altered soil nitrogen cycling microbial processes and decreased nitrogen bioavailability in tropical Australia - ResearchOnline@JCU

Sugarcane cultivation altered soil nitrogen cycling microbial processes and decreased nitrogen bioavailability in tropical Australia - ResearchOnline@JCU Journal

Sugarcane cultivation altered soil nitrogen cycling microbial processes and decreased nitrogen bioavailability in tropical Australia - ResearchOnline@JCU

Supporting Sources (19)

Additional references from the underlying research that informed this benchmark.

Preview of 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, accessed August 5, 2025

Contextual Support

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

Preview of Controls over soil microbial biomass responses to carbon amendments in agricultural systems: A meta-analysis - ResearchGate, accessed July 18, 2025,

Controls over soil microbial biomass responses to carbon amendments in agricultural systems: A meta-analysis - ResearchGate, accessed July 18, 2025,

Contextual Support Journal

Controls over soil microbial biomass responses to carbon amendments in agricultural systems: A meta-analysis - ResearchGate

Preview of Global negative effects of nitrogen deposition on soil microbes - PMC, accessed July 18, 2025,

Global negative effects of nitrogen deposition on soil microbes - PMC, accessed July 18, 2025,

Contextual Support Journal

Global negative effects of nitrogen deposition on soil microbes - PMC

Preview of How microbial C/N and organic C/N ratio relate ? | ResearchGate, accessed July 18, 2025,

How microbial C/N and organic C/N ratio relate ? | ResearchGate, accessed July 18, 2025,

Contextual Support GreyLiterature

How microbial C/N and organic C/N ratio relate ? | ResearchGate

Preview of Innovative Organic and Regenerative Agricultural Production - MDPI, accessed July 18, 2025,

Innovative Organic and Regenerative Agricultural Production - MDPI, accessed July 18, 2025,

Contextual Support Journal

Innovative Organic and Regenerative Agricultural Production - MDPI

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

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

Contextual Support GreyLiterature

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

Preview of Is there any harmful effect of agrochemicals use on soil microorganisms? - ResearchGate

Is there any harmful effect of agrochemicals use on soil microorganisms? - ResearchGate

Contextual Support GreyLiterature

Is there any harmful effect of agrochemicals use on soil microorganisms? - ResearchGate

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,

Contextual Support GreyLiterature

www.soilquality.org.au

Preview of Microbial biomass, carbon and nitrogen stocks across land uses and soil types in the Brazilian tropical dry forest region - alice Embrapa, accessed July 18, 2025,

Microbial biomass, carbon and nitrogen stocks across land uses and soil types in the Brazilian tropical dry forest region - alice Embrapa, accessed July 18, 2025,

Contextual Support Journal

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

Preview of Regenerative agriculture in Australia: the changing face of farming - Murdoch Research Portal, accessed July 18, 2025,

Regenerative agriculture in Australia: the changing face of farming - Murdoch Research Portal, accessed July 18, 2025,

Contextual Support Journal

View of Efficacy of the Ecosystem Services Approach in Transitioning to Regenerative Agriculture in Australia | Reinvention

Preview of ResearchOnline@JCU - James Cook University, accessed on June 7, 2025

ResearchOnline@JCU - James Cook University, accessed on June 7, 2025

Contextual Support Journal

Variation in soil microbial biomass in the dry tropics: impact of land-use change

Preview of Soil and water best management practices for NSW banana growers, accessed July 18, 2025,

Soil and water best management practices for NSW banana growers, accessed July 18, 2025,

Contextual Support GreyLiterature

Soil and water best management practices for NSW banana growers

Preview of Soil Carbon Sequestration Potential: A review for Australian agriculture - MLA, accessed August 5, 2025,

Soil Carbon Sequestration Potential: A review for Australian agriculture - MLA, accessed August 5, 2025,

Contextual Support GreyLiterature

Coexistence of shrubs and grass in a semi-arid landscape: a case study of mulga (Acacia aneura, Mimosaceae) shrublands embedded in fire-prone spinifex (Triodia pungens, Poaceae) hummock grasslands - CSIRO PUBLISHING | Australian Journal of Botany

Preview of Soil microbial biomass and organic carbon - Eurofins, accessed August 28, 2025,

Soil microbial biomass and organic carbon - Eurofins, accessed August 28, 2025,

Contextual Support Journal

Soil Microbial Biomass: A Crucial Indicator of Soil Health

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

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

Contextual Support 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

Preview of Soil microbial biomass: A key soil driver in management of ecosystem functioning, accessed July 16, 2025,

Soil microbial biomass: A key soil driver in management of ecosystem functioning, accessed July 16, 2025,

Contextual Support Journal

Topsoil microbial biomass carbon pool and the microbial quotient under distinct land-use types across China

Preview of Tillage, Microbial Biomass and Soil Biological Fertility | Fact Sheets | soilquality.org.au, accessed July 18, 2025,

Tillage, Microbial Biomass and Soil Biological Fertility | Fact Sheets | soilquality.org.au, accessed July 18, 2025,

Contextual Support Government

Tillage, Microbial Biomass and Soil Biological Fertility | Fact Sheets | soilquality.org.au

Preview of Understanding the economics of horticultural management practices ..., accessed July 18, 2025

Understanding the economics of horticultural management practices ..., accessed July 18, 2025

Contextual Support Journal

Regenerative agriculture augments bacterial community structure for a healthier soil and agriculture - Frontiers

Preview of www.soilquality.org.au, accessed July 18, 2025,

www.soilquality.org.au, accessed July 18, 2025,

Contextual Support Government

www.soilquality.org.au, accessed July 18, 2025,

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Agricultural Crop Production
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 5 Jun 2026

Notes

No upper detrimental threshold — higher values are always better up to natural saturation. Soils falling below this threshold suffer from depleted SOC and nutrient pools, poor soil structure, low carbon use efficiency, and increased susceptibility to disease and environmental shocks. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

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