Soil is one of the most complicated biological materials on our planet.

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The International Union of Soil Sciences (IUSS) is the global union of soil scientists. The objectives of the IUSS are to promote all branches of soil science, and to support all soil scientists across the world in the pursuit of their activities. This website provides information for IUSS members and those interested in soil science.

Universal Soil Classification System Working Group


IUSS Universal Soil Classification System Working Group

The International Union of Soil Sciences Working Group for Universal Soil Classification System (USCS) was officially established by an IUSS Council decision in August of 2010 at the World Congress of Soil Science in Brisbane, Australia and renewed in June of 2014 at the World Congress of Soil Science in Jeju, South Korea. The charge for the Working Group includes development of common standards, methods and terminology in soil observations and investigations and the development of a universal soil classification system.


Activities of the Universal Soil Classification System Working Group

The USCS working group is organized and composed of representatives from countries from all continents with currently applied classifications systems along with representatives from relevant organizations.
The working group has devised a framework of task groups and priorities that were built for moving forward with the effort to provide harmonized criteria for describing and analyzing soil and work needed to understand gaps in existing soil classification and researching the potential for an overarching soil classification system that can be accepted globally, is based on available data, utilizes new technologies, can easily facilitate the use of new data and can position Soil Science discipline to react to the vast amounts of data (high resolution raster information systems) that is currently being produced and how soil classification can be applied to this new data model of information.

The framework is built into 3 distinct categories
  1. Soil Classification Issues
  2. Diagnostic and Soil Profile Information Harmonization
  3. Important Information relating to Soil Classification

Key areas of progress from the above categories are the following:

  • Cold Soil Group -elaboration the classification system for cold (not only permafrost-affected) soils;
  • Tropical Soils – Define diagnostics and major properties for soils that are developed in the tropical regions
  • Development of a data centroid approach to soil classification
  • Evaluation of diagnostic criteria from existing soil classification systems
  • Compare guidelines for field profile descriptions (redox, structure, color, consistency, texture, etc.)
  • Compare and compile horizon nomenclature, designations, definitions
  • Development of a horizon classification system – Research and develop a process that will provide categorization of soil characterization data into logical groupings for surface horizons
  • Moisture and Temperature Regimes – Define potentials for the development of soil moisture and temperature regimes world

When & Where

Meetings of the Universal Soil Classification Working Group

  • Full meeting of the working group-June 14, 2014, Jeju, South Korea
  • Partial working group meeting, November, 2014, in conjunction with the Soil Science Society of America meeting in Long Beach, CA
  • Partial working group meeting, November, 2014, in conjunction with the 20th Latin America Soil Congress, Cuzco, Peru
  • Full meeting of the working group, June, 2015 in conjunction with the IUSS Digital Soil Morphometric conference, Madison, WI

Soil message

Universal Soil Classification

As the Working Group has deliberated options for the future of a universal soil classification system, a data centroid-based approach is being seriously researched. This involves analyzing databases to make allocations of soil properties into logical clouds designed to recognize “Great Soil Groups.” The Great Soil Groups will be equivalent to the great group level from U.S. Soil Taxonomy, along with similar levels in the World Reference Base, Australian Soil Classification, and other defined soil classification systems. The Great Soil Groups will have taxa developed that will document more and less detail. Lower taxa in the system will potentially recognize anthropogenic features, family criteria, climate and other important use and management characteristics. Higher taxa in the system can be developed for meso- and macroscale applications. As more data are added to the system, taxonomic distance calculations can be used to determine if new categories are needed based on tolerances that are set. This system can then be more scalable based on the objective analyses of the data that are collected and entered into the system.