عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Regarding the fact that the center pivot system is manufactured in the country, therefore, conducting a research on its consistency with the climatic and soil conditions in Iran and optimizing its efficiency are necessary. Four irrigation machines (No. 1, 4, 5 and 13) were chosen in Javien Khorasan on the basis of crops irrigated by each system, the length of lateral, elevation difference of radial rows and farm management. First of all, soil, plant and climatic conditions of the region and operational problems of system were investigated. Problems observed in existing systems were such as incorrect height of nozzles for crop. Failure of system to stop in emergency conditions, variation of discharge and pressure in the system, bogging down into mud and unevenness and uniformity of the slope of the land in the research field. In order to measure the evaluation indices, sampling catch cans were laid in two radial rows with 5 meters spacing and then all of the required factors for evaluation were identified. The average value of distribution uniformity for irrigation machines (No. 1, 4, 5 and 13) was 79.1, 80.4, 79.1 and 78.4 percent, respectively during.irrigation season, with the overall average of 79.2 percent. The average value of uniformity coefficient for each system during irrigation season was 82.7, 83.4, 84.3 and 81.1 percent respectively with the overall average value of 82.9 percent. The average value of PELQ for each system was 71.5, 73.2, 66.8 and 71.3 percent during irrigation season, with the overall average value of 70.6 percent. The average value of evaporation and wind losses for each system was 9.6, 9.7, 14.8 and 9.5 percent, respectively with the overall average value of 10.7 percent. The analysis of evaluation factors showed that the systems have relatively low DU and PELO values, which could be most probably due to poor performance of these systems and existing climatic conditions in the study area. The lower PELQ value and higher evaporation loss in system No. 5 was related to high operational pressure and high temperature.