Studies on the Micromorphology of Salt-Affected Soils from El-Fayoum Depression, Egypt

Abstract

Salt-affected soils exhibit considerable areas in Egypt. Salt accumulation affects soil’s biological, physical, chemical, and micromorphological characteristics. Present study focuses on the identification of micromorphological features related to salinization processes in El-Fayoum area. The salts accumulate as surface crust, subsoil accumulation, and random salt distribution in the profile. The studied soils belong to three soil orders: Aridisols (Haplic Natrargids, Typic Haplosalids, and Typic Haplocalcids), Entisols (Vertic Torrifluents, Typic Torrifluvents, and Typic Torripsamments), and Vertisols (Typic Haplotorrerts). The thin section study under the polarizing microscope revealed spongy microstructure due to surface salt accumulation, occurrence of halite and gypsum crystals in voids and s-matrix, and medium to coarse calcified shell fragments distributed throughout the soil profiles, especially adjacent to saline Qaroun Lake. Other micromorphological features identified are subangular blocky microstructure in the Btz horizon of saline-sodic soil-presenting natric horizon; clay papules with high level of clay orientations in the form of sepic plasmic fabric; false micro-aggregates formed due to high level of salts, precipitated clay particles under sodic environment, which have a natric horizon in the presence of CaCO3 more than 13%; and humus accumulations as highly humified debris and patches randomly distributed in s-matrix, especially in the topsoil.