Comparison of Water Use in Pistachio Orchards under Saline Conditions with Water Requirement and Actual Evapotranspiration Estimated by SEBAL Method in Bahadoran Plain in Yazd Province

Pistachio is the most important export product of Iranian agricultural sector. This product is very important because of valuation, job creation, value added as well as tolerance to salinity and drought. The purpose of this study was to investigate and analyze the evapotranspiration of pistachio (ETc and ETa), gross water requirement (IWR), and depth or volume of water used in pistachios (AW) in several selected gardens in Bahadoran region of Yazd province. The study area is one of the pistachio growing centers in Yazd province. The results show that the total annual irrigation water depth in the selected orchards varies from 823 to 1600 mm (equal to 0.27 to 0.57 L/s/ha). However, due to the salinity of irrigation water and to overcome the problems of accumulation of salts in the soil, the hydromodule necessary to supply the water needed for pistachios varies from 0.6 to more than 1 L/s/ha. According to the critical condition of the water resources in the plain, it is virtually impossible to provide it. Also, by using Surface Energy Balance Algorithm, the actual evapotranspiration of pistachios during the growing season was 556 mm for the whole study area and 672 mm for the selected orchards. Regarding the comparisons between pistachio water demand, actual evapotranspiration, and volume of water used in the selected orchards, a managed deficit irrigation strategy can be recommended for the study area. Optimization of traditional irrigation systems, changes in water utilization system with the aim of reducing irrigation interval, considering the spatial variations of pistachio water requirement in the region, off-season leaching, and implementation of proper management at the orchard level are among the solutions that can be useful in overcoming the salinity and water shortage problems and prevent product loss.