ISO 23611-4:2022

Overview

ISO 23611-4:2022 - Soil quality - Sampling of soil invertebrates - Part 4 - specifies a standardized method for sampling, extraction and identification of soil‑inhabiting nematodes from terrestrial field soils. The standard defines field sampling, laboratory extraction (recommended: Oostenbrink elutriator method), counting, fixation and identification procedures as a prerequisite for using nematodes as bio‑indicators of soil quality. It applies to all terrestrial biotopes where nematodes occur and excludes aquatic nematodes.

Key topics and technical requirements

• Sampling design
  • Use small cylindrical cores (≈2 cm diameter; 10 or 15 cm length) or auger; combine cores into a bulk‑sample for homogeneous areas.
  • Protect samples from temperature fluctuations, water loss and mechanical disturbance during transport and storage (storage recommended ≤4 weeks at 4 °C).
• Extraction principle
  • Recommended Oostenbrink elutriator (model III) for routine extractions: uses upward water current to suspend nematodes, followed by sieving (three sieves, mesh ~45 µm) and transfer to a cotton‑wool filter for active movement separation.
  • Suitable soil subsample sizes for Oostenbrink: typically 100–500 g.
  • Alternative methods (e.g., Baermann funnel/tray) are discussed in informative annexes.
• Post‑extraction processing
  • Produce a 100 ml nematode suspension; count in two 10 ml aliquots.
  • Concentrate, fix and mount nematodes on mass slides (300–400 individuals per slide).
  • Identify a minimum number of individuals (e.g., at least 150 or a defined percentage of the sample) to family/genus/species using morphological keys.
• Ecological assessment
  • Uses ecological classifications such as the colonizer–persister (cp) scale and indices like the Maturity Index for soil quality assessment.

Applications

• Environmental monitoring and long‑term soil biodiversity surveys
• Soil quality and habitat assessment using nematode community structure
• Regulatory and impact studies (e.g., evaluation of chemical effects on soil fauna)
• Agricultural advisory and phytosanitary investigations
• Research in nematology, soil ecology and bio‑indication

Who should use it

• Soil scientists, ecologists and nematologists
• Environmental monitoring laboratories and biodiversity assessment programs
• Agricultural consultants and phytosanitary services
• Regulatory agencies and remediation project teams

Related standards

• ISO 18400‑101 (sampling design for field studies)
• Other ISO 23611 parts (earthworms, collembolans, enchytraeids, macro‑invertebrates)
• Soil property standards: ISO 10390, ISO 10694, ISO 11272, ISO 11274, ISO 11277, ISO 11461, ISO 11465
• Relevant testing: ISO 11268‑3

Keywords: ISO 23611-4:2022, soil quality, nematode sampling, nematode extraction, Oostenbrink elutriator, soil bio-indicators, mass slide, Baermann funnel.