Minerals in Clay Fractions of Some Alfisols in Thailand

Abstract

The study on minerals in clay fractions was conducted on thirty selected Alfisols in Thailand. X-ray diffraction (XRD) was used to identify and quantify clay minerals in the samples. The results revealed that minerals in their clay fraction were kaolinite, illite, quartz, smectite, anatase and vermiculite.
Kaolinite and quartz were present in every profile, but illite, smectite, anatase and vermiculite were present only in some profiles. With kaolinite having small size and defect structure as the major clay mineral species and small amounts of vermiculite and illite in the soils, the fertility status of these soils was moderate. Kaolinite alone could contribute substantially on capacity to retain cations in some of these soils. Basing on these findings, nature of these minerals in clay fraction should be carefully considered in soil-fertilizer management for intensive crop production on these soils.