Role of zeolites in persistence of high altitude ferruginous Alfisols of the humid tropical Western Ghats, India

The high altitude ferruginous Alfisols associated spatially with shrink-swe ll soils on the Deccan basalt plateau and dissected table lands in the West ern Chats of India were analysed for their morphological, chemical and mine ralogical properties with a view to comprehend their formation and persiste nce in the tropical humid climate prevailing since the early Tertiary. The study indicates that despite their acidic pH the soils have high bases and their clay fractions are dominated by interstratified smectite-kaolin. The persistence of these non-kaolinitic and/or non-oxidic Alfisols has been pos sible due to the presence of base-rich zeolites of amygdoloidal basalt. It suggests that for an open system such as soil, the existence of steady stat e is a more meaningful concept than thermodynamic equilibrium. The knowledg e gained on the role of zeolites in soils provides a check on the reasoning of models on the formation of soils in tropical humid climate. The study a lso indicates that the supply of bases from zeolites can prevent the soils from losing their productivity even in intense leaching environment. (C) 19 99 Elsevier Science B.V. All rights reserved.