EN ISO 14240-2:2011 PDF

Overview

EN ISO 14240-2:2011 - Soil quality: Determination of soil microbial biomass - Part 2: Fumigation‑extraction method (FE) - specifies a laboratory procedure to estimate soil microbial biomass carbon (C) by lysing microbial cells with chloroform fumigation and measuring the increase in extractable organic carbon. The method is applicable to aerobic and anaerobic (waterlogged/paddy) soils across the full pH range and can also support estimation of microbial nitrogen and ninhydrin‑reactive nitrogen (though the standard text focuses on carbon).

Key topics and technical requirements

• Principle: Chloroform fumigation lyses intact microbial cells; organic material released is extracted with 0.5 mol/L potassium sulfate (K2SO4). Biomass C = difference between fumigated and unfumigated extractable C (EC), corrected by a conversion factor.
• Conversion factor: The standard uses kEC = 0.38 to convert extractable C to biomass C (B C = EC / kEC).
• Fumigation conditions: Chloroform fumigation for ~22–24 h at (25 ± 2) °C with repeated evacuation to remove vapour after fumigation.
• Extraction details: Typical soil:extractant ratio 1:4 (adjustable up to 1:30 for high organic soils). Shake and filter extracts; recommended shaking speeds and times (horizontal shaker 200 r/min for 30 min or overhead 60 r/min for 45 min).
• Analytical options: Measure extractable organic carbon by dichromate oxidation (wet chemical back‑titration) or instrumental spectrometric analysis (UV‑activated persulfate oxidation with IR or UV detection).
• Sampling and sample handling: Follow ISO 10381‑6 guidance. Maintain soil moisture >30% water‑holding capacity for uniform fumigation; sieve at about 40% WHC if needed. Freeze extracts at −15 to −20 °C if not analysed immediately.
• Safety and notes: Use ethanol‑free chloroform (light exposure can form phosgene). Potassium dichromate is hazardous. Chloroform affects soil fauna and may lyse root tissues - pre‑extraction of roots is recommended for root‑rich samples (annex B).

Practical applications and users

• Soil testing laboratories measuring microbial biomass as an indicator of soil fertility, biological activity and carbon cycling.
• Agronomists and land managers assessing soil biological health, organic matter turnover and responses to amendments (manure, compost, crop residues).
• Environmental scientists and ecologists monitoring soil microbial responses to land use change, pollution, remediation and carbon sequestration studies.
• Researchers comparing microbial biomass across soils, treatments or time series using a standardized, reproducible method.
• Regulators and certification bodies requiring standardized soil quality metrics.

Related standards

• EN/ISO 14240‑1: Substrate‑induced respiration (SIR) method for microbial biomass.
• ISO 10381‑6: Soil sampling for laboratory assessment of microbial processes.
• ISO 10694: Determination of organic and total carbon.
• ISO 11465: Gravimetric water content and dry matter.

Keywords: soil quality, microbial biomass, fumigation‑extraction method, EN ISO 14240‑2:2011, soil microbial carbon, chloroform fumigation, potassium sulfate extraction, extractable organic carbon, soil testing, laboratory method.