PHYSICO-CHEMICAL AND PHYSICAL PROPERTIES OF HALLOYSITE RICH SOILS IN GUADELOUPE

In Guadeloupe, under moderate humid climatic conditions (1800 - 3000mm.), hydrolysis of young andesitic parent rock lead to the pedogenesis of 1:1 lattice clay (halloysite) rich soils (Rusty brown soils). But in the old, highly weathered north-eastern part of the island, covered by ferrallitic soils, halloysite equally appears to be the major mineral soil constituent. For the latter soils, in addition to the dominant 1:1 lattice clay, the presence of accessory 2:1 clay minerals has been noted. In these highly impoverished soils, the presence of such 2:1 minerals causes an important variability of physico-chemical properties, in particular the cation exchange properties and the occurence of exchangeable aluminium. Soil water properties of halloysite rich soils show remarkable differences with regard to water retention, total porosity and shrinkage. In addition to their minera1ogica1 nature, the morphology and size of the halloysite particles, as well as their spatial arrangement seem to play a leading part with regard to the soil's physical behaviour