Red Ferruginous Soils: Pedology, Mineralogy and Taxonomy

Abstract

Red ferruginous (RF) soils of Indian tropical environments belong to five taxonomic soil orders (Entisols, Inceptisols, Alfisols, Mollisols and Ultisols), which clearly indicate that tropical RF soils in India have captured wide soil diversity. The spatially associated Ultisols with acidic Alfisols and Mollisols in both zeolitic and non-zeolitic parent materials in humid tropical (HT) climatic environments provides a unique example of tropical soil formation. Such soil formation discounts the exiting conceptual models on tropical soils. For a long time, this fact was not much appreciated, until the role of zeolites and other base rich parent materials was implicated in pedology and edaphology by the Indian soil scientists and soil mineralogists during the last two decades. Indian tropical soils support multiple production systems and generally maintain positive organic carbon balance. The recent developments on the pedology of RF soils, including their physical, chemical, biological, mineralogical and micro-morphological properties are very timely as the new knowledge improves the understanding as to how the parent material composition influences the formation of Alfisols, Mollisols and Ultisols in weathering environments of HT climate. This knowledge also explains how the relict Alfisols of semi-arid tropical (SAT) areas is polygenetic created by climate shift during the Holocene. Pioneering research efforts have improved the basic understanding of why the formation of Oxisols from Ultisols is an improbable genetic pathway in tropical environment of India and elsewhere in the world. There is a strong need to modify the mineralogy class of highly weathered RF soils. This basic information will help to dispel some of the myths on the formation of tropical soils and their low fertility.