ABSTRACT
231We briefly review the history of soil classification in the tropics and trace the development of Soil Taxonomy relative to tropical soils. Although significant progress has been made in this regard, there remain several areas that need improvement. These include the following issues that are addressed in this chapter: (1) the undocumented change in the definition of the “iso-” soil temperate regimes, which increased the delta T from 5°C to 6°C; (2) the questionable criteria for the spodic horizon, which disagree with classical concepts of pedology; (3) the case of Mollisols with an aridic soil moisture regime, which are illogically classified as Ustolls; (4) the problem of extremely acid, wet Vertisols, some of which are now classified as Aquerts, thus being recognized for their 232most limiting characteristic only at the subgroup level; (5) the ambiguity of “Pale” great groups, which include soils with thick argillic horizons and soils in which the subsoil high clay content is inherited from the parent material; (6) the dilemma of paddy soils, whose classification fails to capture the particular conditions of these soils; and (7) the predicament of the kandic horizon, whose introduction may not have been warranted. We examine these issues in some depth, and present possible solutions.
