Perspectives on soil series classification based on comparison of two contrasting scenarios

Abstract

The soil series category is the lowest category in taxonomic soil classification. Series are thus the most narrowly defined soil units in taxonomic soil classification. Appropriately constructed soil series classification is, therefore, vital for effective communication about soils and for enabling and enhancing effective land suitability evaluation, land use planning, technology transfer and sustainable land use and soil management. Thus, the concept is that soil series must be pragmatic. They must be uncomplicated and simple to make it easy for soil scientists other than pedologists to understand them and use them. To achieve this, soil series must have well-defined class limits and must be mutually exclusive. Soil texture is a critically important parameter in soil series classification. Simplified soil series fit these requirements. So-called classical soil series, based on identification of natural soil bodies, do not fit the requirements for soil series classification. Some natural soil entities exhibit a narrow range of soil properties. These soil entities can then be more readily recognized and their contributions to the ecological services in the natural environment more readily understood. Others may span a much larger large range of soil properties that confounds soil interpretation implications. Debate also centers on which soil, or environmental property, to use in defining the natural entity. Texture and soil ionic properties are probably the most extensively researched. However, underlying geology formations, climate and geography considerations also featured in their identification to date. The different histories and implementation of soil series classification in the United States of America (USA) and the Republic of South Africa are compared. The way that soil series are defined and used in the USA and the successful soil series classification in the 1977 South African soil classification system could also serve as models of how to approach soil series classification in other countries.