Effect of Irrigation Regime on Mineralogical Properties of Clay Fraction in some Iraqi Rice Soils

Abstract

Five soil pedons were chosen from two sites in Najaf and Diwaniyah, governorates, represent some of the soils of Middle Euphrates area. The soils are exploited by rice crop, and irrigated by two methods (flooded and dry) during the growing season. The mineralogical composition of < 2μm fractions for two depths (0-30 and 31-60 cm) in all studied soils were examined by X-ray diffractions. Results showed the presence of Mica, Smectite, Real chlorite and Kaolinite minerals in clay fraction of soils irrigated by the wet method. Results also, showed the precipitation of Brucite layer into Montmorillonite interlayers and caused to shifting Montmorillonite towards Chlorite mineral in soils irrigated by the dry method, and this was attributed to creation a suitable conditions from continuous wet-dry cycling, which encouraged a chloritization phenomenon to occur in these soils.. While, the continuous waterlogging process did not affect much on the weathering of mica minerals, and transformed it towards of expandable 2:1 minerals in these soils.