IMPACT OF IRRIGATION ON MICROMORPHOLOGICAL FEATURES OF DESERT SOILS OF HADRAMOUT-VALLEY (YEMEN)

The integrated micro-, macromorphological, and chemical research revea led a considerable contribution of rock inherited properties in saline desert soil of Hadramout Valley; these are microlamination, microhete rogeneity, high carbonates and salts content, prominent microstructure and porosity, loose fabric and abundance of mica minerals varying in chemical composition and size. Extreme bioclimatic conditions account for the high rate of organic residues mineralization, low humus concen tration in plasma, weak biogenic reworking, strong salinization. Soil desalinization rate is shown to depend mainly on the duration of irrig ation. Thus an active salt removal from the upper root inhabited layer is observed already in newly irrigated soils, while in the anciently irrigated ones the carbonates and gypsum are partially leached. Irriga tion does not promote clay illuviation.