World Reference Base (WRB)
Definition
The FAO-IUSS international soil classification standard, with 32 Reference Soil Groups; mandatory vocabulary for ENFSI forensic soil evidence reports.
- Issuing bodies
- FAO and IUSS
- Scope
- International soil classification standard
- Reference Soil Groups
- 32
- Forensic use
- Mandatory vocabulary for ENFSI soil evidence reports
Common questions
Why does a forensic soil report need to use WRB terminology specifically?+
ENFSI requires a common, internationally recognised vocabulary so that soil classification terms in a report mean the same thing across laboratories and jurisdictions, avoiding ambiguity that could arise from using a national or regional classification system instead.
How is the WRB different from a national soil classification system a country might already use?+
National systems are often tailored to a country's own soils and agricultural needs, while the WRB is designed to be applicable globally and to allow soils from different countries to be classified and compared using the same set of Reference Soil Groups.
Related terms
- A Horizon
- The uppermost mineral soil horizon, darkened by organic matter accumulation and the layer most commonly transferred by footwear and vehicle contact.
- Chroma
- The saturation or colourfulness of the hue, from 0 (neutral grey) outward in whole-number steps. Strongly weathered, iron-oxide-rich soils have high chroma;...
- Clay Mineral
- A secondary phyllosilicate mineral produced by chemical weathering; includes kaolinite, illite, smectite, and chlorite, all diagnostic of parent material and weathering intensity.
- Hue
- The dominant wavelength family of a colour, expressed as a position on the Munsell colour wheel. Soil hues run from 10R (red)...
- Loss on Ignition (LOI)
- Weight loss after heating dried soil to 550 degrees Celsius. Approximates the organic matter content. A simple, cheap, high-yield discriminator in field...
- Munsell Chip Comparison
- The visual procedure of matching a soil sample against printed colour chips in the Munsell Soil Colour Chart under standard daylight conditions,...
- Munsell Notation
- A three-component colour code (Hue-Value/Chroma) standardised under ASTM D1535 for describing soil colour from the Munsell Soil Colour Chart.
- Particle-Size Distribution
- The quantitative measurement of the proportions of gravel, sand, silt, and clay in a soil sample, determined by sieving and hydrometer or...
- Soil Texture
- The relative proportions of sand, silt, and clay in the mineral fraction of a soil, expressed as a USDA or ISSS texture...
- USDA Soil Taxonomy
- A hierarchical classification of soils into 12 orders based on pedogenic processes and measurable diagnostic properties; the primary reference for US forensic...
- Value
- The lightness dimension of the Munsell system, scaled from 0 (theoretical black) to 10 (theoretical white). High-organic soils tend to have low...