Overview
ISO 16072:2002 - Soil quality - Laboratory methods for determination of microbial soil respiration specifies laboratory procedures to measure microbial respiration of aerobic, unsaturated soils. The standard covers methods to quantify O2 uptake or CO2 release, either as basal respiration (no added substrate) or substrate‑induced respiration (SIR) after nutrient addition. ISO 16072 supports assessment of microbial activity, effects of additives, estimation of microbial biomass and calculation of the metabolic quotient (qCO2).
Key topics and technical requirements
- Scope and purpose: Measurement of microbial respiration in aerobic, unsaturated soils to determine activity, additive effects, microbial biomass and qCO2.
- Terminology: Defines basal respiration, substrate‑induced respiration (SIR), microbial activity, metabolic quotient qCO2, rate of CO2 formation/O2 consumption and microbial biomass.
- Sampling and pre‑treatment: Refers to ISO 10381‑6 for collection, handling and storage; soils must be sieved and pre‑incubated as prescribed.
- Incubation conditions:
- Water status strongly affects respiration - optimal pore water pressure ~ −0.01 to −0.03 MPa (≈40–60% of maximum water‑holding capacity).
- Temperature control is required; 20–30 °C generally recommended; use 22 °C when determining microbial biomass.
- Choice of measurement method: Investigators select between O2 uptake and CO2 release methods; results from the two are not strictly interchangeable.
- O2 uptake methods (e.g., pressure‑compensation static incubation) are preferred for alkaline or high organic soils where abiotic CO2 release may occur.
- CO2 measurement methods include titration (NaOH absorption + HCl back‑titration), coulometry, infrared gas analysers (IRGA) in flow‑through systems, gas chromatography, and pressure measurements.
- Analytical details: Example - the titration method uses NaOH absorption of CO2 and back‑titration with HCl; calculation factors depend on reagent concentrations and sample dry mass.
- Replicates and controls: Methods call for triplicates and reagent/blank controls to ensure valid results.
Applications and who uses it
ISO 16072 is used by:
- Soil scientists and microbiologists measuring microbial activity and biomass
- Agricultural and environmental testing laboratories assessing soil health
- Remediation and waste management specialists evaluating pollutant effects on soil microbes
- Researchers calculating qCO2 for ecosystem and carbon‑cycle studies
- Regulatory agencies requiring standardized soil respiration data
Practical uses include comparing management practices, testing fertilizers or contaminants for biological impact, and supporting carbon‑budget or soil‑quality monitoring programs.
Related standards
- ISO 10381‑6 - Soil sampling for aerobic microbial assays
- ISO 11274 - Water‑retention characteristic laboratory methods
- ISO 11465 - Determination of dry matter and water content
Keywords: ISO 16072, soil quality, soil microbial respiration, basal respiration, substrate‑induced respiration, O2 uptake, CO2 release, metabolic quotient, laboratory methods.