Principles of soil classification and the future of the South African system

Abstract

Humans classify their environment to create order, make it understandable, aid recollection and to communicate. The nature of these classifications is not always understood, because they are learnt from an early age. Building on these principles provides a sound basis for any scientific classification. This paper explores these principles, those of the USDA Soil Taxonomy, the World Reference Base for soil resources, and the South African Soil Taxonomy. Knowledge should be ultimate aim of soil classification. A hierarchical system with four levels is proposed for the South African Soil Taxonomy. This can easily be achieved by adding a higher level, proposed to be called a Soil Group, to the current three levels (form, family, and phase). The South African Soil Taxonomy must guard against too many taxa, because humans have a limited ability to comprehend numerous taxa. The distinguishing criteria between taxa should be more clearly defined, while at the same time guarding against becoming too data hungry. The classification should not shy away from intergrades. The object being classified (soils) is a natural system and intergrades will necessarily occur. It is proposed that these should be classified as intergrades, rather than trying to artificially separate natural soil bodies.

Keywords: soil classification, USDA Soil Taxonomy, World Reference Base

South African Journal of Plant and Soil 2013, 30(1): 23–32