A revised perspective on principles of soil classification in South Africa

Abstract

Limited significance has been given to the formal recognition of certain subsoil materials in the South African Soil Classification System. Three principles in the current classification system are discussed using variants of soil profiles associated with the Avalon soil form. The retention of the arbitrary depth criterion is questioned in favour of the recognition of an enlarged ‘sphere of pedological interest’ extending formal classification to deeper soil materials. This implies that a greater number of soil classes will be required but these additional classes may be accommodated by recognising an additional soil group class in the classification system. It is proposed that the definitions of diagnostic horizons be rewritten to focus on the central concept of the horizon properties, dispensing with limitations on the nature of overlying or underlying horizons. An open class structure to the classification system is advocated.