It is possible to have more than one classification for the same soil, depending on which soil forming process is assumed to be expressing itself. Due to this and other problems, the USDA abandoned its system based on soil forming processes and developed the system layed out in Soil Taxonomy based on existing quantifiable characteristics. Engineers also use systems based on existing characteristics, for obvious reasons. Criteria for distinguishing soils are not necessarily the same for different classification systems. Soil texture is a good example of the problems involved in correlating classifications between two or more systems.
Texture describes the proportion of different size classes of the mineral part of the soil.
For the same soil, texture-class names can differ depending on the classification system used. Other physical, chemical, and biological characteristics have similar discrepancies between systems which makes one to one correlation between systems nearly impossible unless a detailed soil description is available. Hierarchical, descriptive, or nominal systems of classification each have their strengths and weaknesses. Rules of hierarchical systems allow one to determine the highest to lowest levels of classification without previously knowing any of the possible classifications. Also, these systems can make trivial distinctions when applied in areas of the world different from those where they were developed.