Investigating the effect of some factors of sprinkler building irrigation system and its management on uniformity coefficient in sprinkler irrigation

The uniformity of water distribution in the field affects all irrigation indicators from the aspect of water and soil conservation. When the uniformity coefficient is low, application efficiency decreases; consequently, the product yield decreases and increases surface water and deep percolation losses. Factors affecting water distribution uniformity in sprinkler irrigation are classified into four groups: sprinkler building, irrigation system, system management, and climatological factors. In this study, the effect of rotation speed and rotation factor of sprinkler (sprinkler building), sprinkler riser height, working pressure, arrangement and distances of sprinklers (irrigation system), and irrigation time (system management) in field conditions on uniformity coefficient were investigated. Also, the diameter of water collection containers was evaluated on the tests results.

This research was conducted on the research farm of Kurdistan University located in Dushan village of Sanandaj city. In the present study, were used from R8 Komet and Luxor Sprinklers. The Sprinkler irrigation model was performed by the single sprinkler method, and the experiments were done according to ISO15886-3: 2021 standard. An area of 3600 m2 was networked to the center of the sprinkler, a square grid of 3*3 meters. In each network vertices, two models of containers with two inner diameters of 80 and 180 mm and a height of 90 and 200 mm, respectively, were placed to collect water. The pressures tested for both sprinklers were 30 and 40 m. The experiments used two test times (1 and 3 h), two average rotation speeds (1.5 and 3.5 rpm), and two sprinkler riser heights of 1 and 2 m. The sprinklers arrangement and distances included 18×18, 24×24, and 27×27 in the square and triangular arrangements, and 21×15, 27×21, and 24×30 in the rectangular arrangement. At the end of each experiment, the water volume of the collection containers was measured by a graduated cylinder. All experiments were performed in 3 replications. Also, the wind speed was measured every 15 minutes by EXTECH 45158 tricycle device. Christiansen uniformity coefficient (CU) was used to calculate the uniformity of sprinkler water distribution. The research was conducted in a completely randomized block design with the factorial experiment. SPSS 22 software was used to analyze the data.

1. The effect of container diameter on CU was not significant. 2. The uniformity coefficient of the two sprinklers has a significant difference. 3. The effect of the arrangement and riser height of the sprinklers in the two low and mild wind speeds on the CU is insignificant. 4. The effect of two low and mild wind speeds on CU was insignificant. 5- The effect of working pressure and sprinkler distances in the two low and mild wind speeds on CU are significant. 6- The effect of irrigation time on the uniformity coefficient is significant. 7- The effect of sprinkler rotation speed was significant on CU.

The minimum diameter mentioned for water collection containers, according to the ISO15886-3 standard, is sufficient for the conditions of the experiments of the present study. The Sprinkler rotation is effective on the uniformity coefficient. CU of Komet sprinkler is acceptable for all crops of agronomy and garden, but the Luxor sprinkler is only suitable for garden crops. Only part of the decrease in uniformity due to increasing the distance of sprinklers can be compensated by increasing the pressure. Increasing the irrigation time is effective in improving the uniformity coefficient. Increasing the rotation speed of the sprinkler due to repairs can effectively reduce the uniformity coefficient.