Molecular microbial biomass
Microorganisms (bacteria and fungi) are the most abundant and most diverse within soil biodiversity. Molecular microbial biomass allows to measure the abundance of microorganisms in the soil, based on the total microbial DNA.
Standard
NF EN ISO 11063: Soil quality - Direct extraction of soil DNA
Sampling and logistics
Analysis on fresh soil.
Description of the measurement method
Total microbial DNA is extracted by chemical and physical lysis, then quantified by various methods (agarose gel electrophoresis, fluorimetry or photometry). Molecular microbial biomass is then estimated from this DNA quantity.
Example ranges
| Situation | Min | Max | Median |
|---|---|---|---|
| Large crops (885 observations) | 2 µg DNA/g soil | 306 µg DNA/g soil | 32 µg DNA/g soil |
| Grasslands (536 observations) | 2 µg DNA/g soil | 455 µg DNA/g soil | 65 µg DNA/g soil |
| Vineyards and orchards (42 observations) | 2 µg DNA/g soil | 249 µg DNA/g soil | 14 µg DNA/g soil |
| Forests (584 observations) | 2 µg DNA/g soil | 629 µg DNA/g soil | 53 µg DNA/g soil |
Source: Soil Quality Measurement Network (RMQS, GIS-SOL, 2011), sampling at 0-30 cm
Interpretation
This indicator informs about the abundance of microorganisms. It can be interpreted in relative comparison (comparison between two practices or over time).
It should be interpreted according to certain soil physico-chemical parameters, notably texture, pH, and organic carbon content.
A reference value can be calculated based on soil characteristics (clay, pH, organic matter) and plot altitude.
Advantages and limitations
Advantage
- Robust and well-referenced method
Limitations
- Extraction procedure may vary between laboratories; it is recommended to use the same laboratory to monitor changes.
- This measurement does not indicate microorganism activity.
- 50-100€
Sources
- Balloy B. et al., (2017). Overview of indicators related to soil organic and biological status. https://agriculture.gouv.fr/tour-dhorizon-des-indicateurs-relatifs-letat-organique-et-biologique-des-sols
- Gis Sol. 2011. The state of soils in France. Scientific Interest Group on Soils, 188 p.
- Karimi et al., 2018 – French atlas of soil bacteria. Biotope, Mèze, National Museum of Natural History, Paris, 192 p.
- RMT Bouclage. 2025. Indicators of biological functioning of agricultural soils. [18/11/2025]. https://www.rmt-fertilisationetenvironnement.org/moodle/pluginfile.php/5041/mod_resource/content/3/Recueil%20indicateurs%20de%20fonctionnement%20biologique%20des%20sols%20agricoles_vf251009.pdf
- Terrat et al.. Meta-barcoded evaluation of the ISO standard 11063 DNA extraction procedure to characterize soil bacterial and fungal community diversity and composition. Microbial Biotechnology, 2015, 8 (1), pp.131-142.
