This study was carried out at the Experimental Laboratory of the Microbiology Department, Soils, Water and Environmental Research Institute, Agricultural Research Center (ARC), Giza, Ornamental Horticulture Department, Faculty of Agriculture, Cairo University, and the Experimental Laboratory of Natural Resources Department, Institute of African Research and Studies, Cairo University, Egypt, during the two successive seasons of 2005/2006 and 2006/2007. The objectives of this work were to isolate and study the characteristics of rhizobia isolated from Acacia saligna against reference strains in order to evaluate their efficiency for nodulation associated with Acacia nilotica subsp. tomentosa, select suitable local carrier materials to prepare an inoculant, and investigate the response of inoculated plants to irrigation water salinity and irrigation intervals.