RAPID WEATHERING KINETICS OF SECONDARY MI NERALS FOREST FERRALSOLS OFCENTRAL AMAZONIA - BAG-MINERAL METHOD

Secondary minerals of soil depend on physical-chemical conditions in t he soil horizons where they form, which are largely controlled by biol ogical activity. Small bags containing various minerals, gibbsite, two kinds of kaolinite, and a silica gel, were introduced in top ferralso l horizons under Amazonian forest, in order to determine the kinetics of dissolution-precipitation reactions. After 6 months in soil, ail th e minerals had been weathered, and newly generated iron and titanium o xy-hydroxides had been formed. The conclusion is that, in the studied soil, secondary mineral reactions to environmental conditions progress in a short time compared with pedological times.