This study has investigated, over two seasons, salinity stress, and two mineral nitrogen fertilizer effects on Acacia gerrardii (Benth.) and Vachellia origena (Hunde.) growth. Photosynthesis and growth characteristics both responded positively to fertilization. Vachellia origena growth improved and become more tolerant to salinity stress by aid of fertilization. Calcium nitrate fertilization has induced the highest seedling height, diameter, and dry weight. The salt concentrations negatively affected growth, particularly 5000 ppm. Calcium nitrate or ammonium sulfate can improve the growth and the biomass of the tree seedlings and increase tolerance to high salinities either in nursery or in the field.