Overview
ISO 11274:2019 - Soil quality - Determination of the water‑retention characteristic - Laboratory methods specifies laboratory procedures to determine the soil water‑retention characteristic (the relation between soil water content and matric pressure). The document applies to measurements of the drying (desorption) curve only and describes four laboratory methods covering the full range of matric pressures used in soil‑physical studies.
Key methods covered (with matric pressure ranges):
- Sand, kaolin or ceramic suction tables: 0 kPa to −50 kPa
- Porous plate and burette apparatus: 0 kPa to −20 kPa
- Pressure plate extractor (pressurized gas): −5 kPa to −1 500 kPa
- Pressure membrane cells (pressurized gas): −33 kPa to −1 500 kPa
The standard also provides guidelines for method selection, sampling and sample preparation, apparatus assembly, procedures, result expression, test reporting and precision.
Key technical topics and requirements
- Scope limitation: Applies only to drying/desorption curves (not wetting curves).
- Method selection: Guidance to choose the most suitable technique based on pressure range, sample size, soil texture and laboratory throughput.
- Sampling & preparation: General requirements for representative sampling and steps to prepare cores/aggregates for laboratory testing.
- Apparatus and assembly: Detailed procedural requirements for suction tables, porous plate/burette systems, pressure plate extractors and pressure membrane cells.
- Procedure & equilibration: Equilibration criteria and stepwise procedures for measuring water content at specified matric pressures.
- Expression of results: Reporting water content as mass ratio or volume fraction, conversions for stony soils and formatting of test reports.
- Precision & quality control: Information on expected precision and the need for replication and instrument maintenance.
Practical applications and users
ISO 11274:2019 is used to produce reliable soil water‑retention data for practical and research applications, including:
- Estimating pore‑size distribution and macro/microporosity
- Assessing plant‑available water for irrigation planning
- Determining drainable pore space for drainage design and pollution risk assessment
- Monitoring structural changes from tillage, compaction or amendments
- Supporting hydraulic‑property estimates (e.g., hydraulic conductivity) and microbiological degradation studies
Typical users:
- Soil scientists and agronomists
- Environmental and geotechnical laboratories
- Irrigation and drainage engineers
- Agricultural consultants and research institutions
Related standards and context
ISO 11274:2019 was prepared by ISO/TC 190 (Soil quality). It replaces ISO 11274:1998 (incorporating its corrigendum) and complements other ISO soil‑quality standards covering sampling, physical and chemical test methods.