Perspectives on the principles and structure of the soil classification system in South Africa: discussion and practical examples

Abstract

The paper discusses revised principles, perspectives and structure for soil classification of natural soils in South Africa. An expanded ‘sphere of pedological interest’ is proposed through the formal recognition of a wider range of subsurface soil materials. The concept of soil groups has been recognised and is further developed as a formal classification category. In addition, a subgroup category is introduced with discussion using practical examples for the eluvial, yellow-brown apedal, and prismacutanic and pedocutanic horizons with the proposed orthic group of soils. Identification of soils within these examples is proposed to follow a formal key sequence that seeks to identify soils with subsurface gleying, and subsequently progressing from those subsurface horizons of generally more intense to less intense weathering. The key structure retains much of the existing soil-form structure. As such it should be readily suitable for implementation. A description for additional subsurface horizons is introduced, which in selected instances differs slightly from that which is currently understood from present definitions. It is advocated that the principle advantage for introducing an expanded sphere of pedological interest will be gained through improved soil recognition and interpretation that could be given to soil classification classes. The proposed structure is open-ended. This should facilitate a new freedom in the examination of soils that could lead to their improved description in both morphological and numerical soil properties.

South African Journal of Plant and Soil 2013, 30(2): 61–68