Formation and properties of aridic soils of Azraq Basin in northeastern Jordan

Abstract

Aridisols occupy a wide and significant part of Jordan. The majority of soils in the Azraq Basin, northeastern Jordan, are aridisols. A database on aridisols and land characteristics in northeastern Jordan is needed to allow rational planning of land and water resources utilization. The objectives of this paper are to: characterize the main soil types in the area, and identify the main processes contributing to their genesis and evolution. For this purpose eight representative profiles were selected for this study and soil samples were collected and their chemical and physical properties were examined in the laboratory. The natural vegetation is desert shrubs and short grasses. The sparseness of the vegetation resulted in low SOM content and the presence of ochric epipedons in all of the studied soils. The genesis of these soils accounts for the accumulation of calcium carbonate, soluble salts, and gypsum in the subsoil. Carbonate, clay eluviation–illuviation, and salt accumulation are the dominant pedogenic processes in these soils. Silt content increased toward the surface indicating eolian activity. Clay content increased with depth indicating illuviation of clay. Clay illuviation and argillic horizon development within these soils is assumed to be a relict feature from presumably more humid climates during the Quaternary. Desert pavements cover the surfaces of these soils and provide a unique obstacle for agricultural development. The major restrictions to agricultural land use in the area are very low infiltration rate, low permeability, and high erodibility. Proper management practices should be adopted if such soils are to be cultivated.