Abstract
ABSTRACT
An assessment of the hydraulic performance of rain gun sprinkler (HIDRA, Italy) with different nozzle sizes and operating pressures under field conditions was carried out. The study was conducted between January – March, 2020 irrigation season at the Institute for Agricultural Research Samaru Zaria, Nigeria. Fifteen treatments comprising of three nozzle sizes 12, 14 and 16 mm (NS1, NS2 and NS3) and five levels of operating pressure, 260, 280, 300, 320 and 340 kPa (OP1, OP2, OP3, OP4 and OP5) were analyzed using Randomized Complete Block Design (RCBD) to determine their effects on the Coefficient of Uniformity and Distribution Uniformity (CU and DU) of the rain gun sprinkler. Other performance parameters obtained from the study were wetted diameter and application rate. The assessment was carried out under the average wind speed of 4.8 km/h and on a soil with the basic infiltration rate of 2.4 cm/h. Water was pumped into the system with the aid of 5.5 hp centrifugal pump at varied pressure to the maximum pressure of 340 kPa. The CU of the Rain gun sprinkler ranged from 66 to 91 % while the DU ranged from 45 to 73 %; and the treatment combination of OP4NS1 showed the highest value of CU and DU, while the treatment combination of OP1NS1 reflected the least value of CU and DU. The application rate ranged from 0.60 to 3.07 cm/h, while the wetted diameter ranged from 20.5 to 32.5 m. Further analysis of the results showed that increasing the operating pressure of the rain gun sprinkler from 260 to 340 kPa increased the CU and DU by 25 and 28 % respectively. Results also revealed that the performance of rain gun sprinkler head were largely influenced by both operating pressure and nozzle sizes with higher performances recorded at moderately higher pressure combined with smaller nozzle size. Operating the rain gun sprinkler at 320 kPa using 12 mm nozzle size recorded significantly higher CU and DU with a wetted diameter of 27.5 m and a reasonable record of application rate value of 1.92 cm/h which is lower than the basic infiltration rate of the soil in the experimental field. Therefore, in order to maximize the water use productivity and conserve the soil in the study area, rain gun sprinkler head should be operated at 320 kPa combined with 12 mm nozzle size.
KEYWORDS
Rain gun sprinkler, Nozzle Sizes, Operating Pressure, Application Rate, Coefficient of Uniformity and Distribution Uniformity.

Key words: Rain gun sprinkler, Nozzle Sizes, Operating Pressure, Application Rate, Coefficient of Uniformity and Distribution Uniformity.