The Effects of Acacia nilotica and Prosopis juliflora as the Nitrogen Provider Trees on the Understory Soil of Them

Trees have noticeable effects on soil resources distribution and its biochemical processes in arid and semiarid regions. Organic materials are naturally much more in the understory soil than that in the open areas soil. This study tries to reveal and compare the effects of Acacia nilotica and Prosopis juliflora trees on the physical and chemical properties of the soil. To achieve the goals, the understory soil of A. nilotica, P. juliflora and the control soil at three depths of 0-20, 20-40 and 4060 cm with three replications, were sampled and analyzed based on the complete randomized block experiment with three replications. The studied parameters including; mineral nitrogen, dissolved organic nitrogen, nitrogen mineralization potential, total nitrogen, organic carbon percentage, lime, EC, pH and soil texture were measured. Likewise, analysis of the criterion plant (Lepidium sativum) was performed to determine the efficiency of Acacia nilotica and Prosopis juliflora trees on the amount of nitrogen absorption. Nearly, in all the studied parameters the two mentioned trees had a significantly different effect on the soil with respect to the control soil. Hence the result confirmed the high potential and positive effects of these nitrogen-fixing trees (NFTs) on the soil quality as compared to the site without these trees. The results of this study also indicated that the both of these trees had increased the amount of soluble organic nitrogen, nitrogen mineralization potential, soil organic carbon content and total nitrogen in the studied plants compared to the control. Meanwhile, in the superficial soil, A. nilotica and P. juliflora remarkably increased the mineral nitrogen and total nitrogen, respectively.