| Abstract: | Abstract Because of widespread Zn deficiency in rice, an experiment was designed to evaluate the Zn fixing capacity of several clay minerals separated from tropical rice soils. The study involved the addition of 25 μg Zn per g of clay as zinc sulphate, incubation at an ambient temperature of 30 C±2 followed by alternate wetting and drying and extraction by 0.005 M DTPA to assess the magnitude of Zn fixation. On average, 57% of the applied Zn was unextractable by 0.005 M DTPA and considered fixed. The dominantly biedellite clay systems possessed the highest capacity to fix Zn (70%), followed by vermiculite (59%) and montmori‐llonite (55%). Clay systems containing hydrous mica impregnated with important proportions of kaolinitic and vermiculitic type minerals fixed 40% of the added Zn. Most of the clays, consisting of mixed mineralogy, fixed more than 50% of the applied Zn. |
