Mineral composition of selected soils in Saudi Arabia

Soil Science Department, Faculty of Agriculture, King Saud University, Riyadh, Saudi Arabia.Ten soil profiles from the agricultural areas in Saudi Arabia were investigated for their mineralogical properties and some general characteristics. It was found that the soils of the eastern region were Torrifluvents and Gypsiorthids, coarse in texture with high salt, gypsum and carbonate contents. Soils of the central region were found to be Torriorthents, Torrifluvents and Torripsamments, medium to coarse in texture with smaller amounts of gypsum and salt than soils in the east. Soils of the western region were Haplargids with minor amounts of carbonate and salt. Carbonate, quartz and gypsum were found to be the main constituents of the sand and silt fractions in soils of the eastern region, while quartz, carbonate and feldspars dominated the sand and silt in the central region. The sand and silt fractions of soils in the west contained mainly quartz, feldspars, hornblende and mica. Palygorskite dominated the clay fractions of soils in the east, while kaolinite was found to be dominant in the central region, and kaolinite, smectite and mica in the west. The mineral composition of the soils was affected by the rocks from which they were derived. Igneous and metamorphic rocks of the Arabian Shield affected the soils in the west, while sedimentary rocks had great influence on soils of the central and eastern regions