Effects of Pressure Changes and Type of Emitter on the Performance of Drip Irrigation Systems in Pistachio Orchards of Yazd Province

The effects of pressure changes and type of emitter on the performance of pistachio orchard’s drip irrigation systems were studied in 21 orchards, under irrigation by saline water. Based on the results, water distribution uniformity in different parts of the orchards (EU) and the average flow of emitters ranged from 71% to 95% and 5.5 to 28.8 l hr-1, respectively. Furthermore, the lowest and highest operating pressure of the emitter were 0.1 and 1.8 bar in different pistachio orchards, respectively. The highest (21%) and lowest (3%) values of coefficient of variation (CV) were obtained from the evaluation of orchards number 13 and 4, respectively. Moreover, the minimum (0.6 %) and maximum (26.2 %) deviation values of the measured average flow from the nominal flow were also observed in orchards No. 3 and 18, respectively. The values of CV in orchards No. 3, 4, 10, 11. 12, 19, and 20 were lower than 10% and were excellent. Orchards No. 2, 13, 14, and 15 with values of about 20% showed good and very good CV, and all of the remaining orchards had very good values of CVs between 10% and 20 %. The results showed that the emitters had a low CV and high EU in the orchards with proper supply and distribution of operation pressure (0.5 to 4 bar) without considering their types and brands. However, the two 8 liters per hour emitters including the Eurodrip and Europlast (King model) for soils with low infiltration rate, and the 26.2 liters/hour Eurodrip emitter for supplying high flow rates with an operating pressure of 0.5 to 1 bar can be recommended. Results indicated that, in most orchards, it is vital to modify the irrigation planning (time and frequency). It seems that if the operating pressure is supplied and distributed properly, emitter clogging and, consequently, EU would not be much affected by water salinity.