چکيده

Excessive use of water for irrigation has lowered underground aquifers and has deteriorated the quality of underground water for irrigation causing agricultural production and water use efficiency to decrease. To study the effect of salinity of irrigation water and application of nitrogen on yield and water use efficiency of pomegranate a split plot experiment with 15 treatments and three replications was performed in city of Saveh in 1389. Treatments were factorial combinations of five levels of salinity (2, 4, 6 and 8 dS/m) for irrigation water and three rates (0, 150 and 300 g) of nitrogen for each tree. The salinity levels of irrigation water were located in main plots and nitrogen rates were considered as subplots using a randomized complete block design. The results showed that the salinity of irrigation water decreased plant yield when it was higher than 4 dS/m. When the salinity levels of irrigation water were less than 4 dS/m reduction in yield was not significant and this salinity level was considered as threshold salinity for pomegranate. At higher salinity levels the yield of pomegranate decreased at the rate of 3.3 percent per each unit of EC of irrigation water. Application of nitrogen increased plant yield at salinity levels lower than 4 dS/m but it decreased pomegranate yield when the salinity levels of irrigation water were higher than threshold salinity. The relative yield of pomegranate at different salinity levels was estimated by an equation and reported in this paper. Keywords: Pomegranate, Salinity of irrigation Water , Water use efficiency, Relative yield, Nitrogen.