Abstract
Variable rate sprinklers (VRS) have been developed to promote localized water application of irrigated areas. In Precision Irrigation, VRS permits better control of flow adjustment and, at the same time, provides satisfactory radial distribution profiles for various pressures and flow rates are really necessary. The objective of this work was to evaluate the performance and radial distribution profiles of a developed VRS which varies the nozzle cross sectional area by moving a pin in or out using a stepper motor. Field tests were performed under different conditions of service pressure, rotation angles imposed on the pin and flow rate which resulted in maximal water throw radiuses ranging from 7.30 to 10.38 m. In the experiments in which the service pressure remained constant, the maximal throw radius varied from 7.96 to 8.91 m. Averages were used of repetitions performed under conditions without wind or with winds less than 1.3 m s-1. The VRS with the four stream deflector resulted in greater water application throw radius compared to the six stream deflector. However, the six stream deflector had greater precipitation intensities, as well as better distribution. Thus, selection of the deflector to be utilized should be based on project requirements, respecting the difference in the obtained results. With a small opening of the nozzle, the VRS produced small water droplets that visually presented applicability for foliar chemigation. Regarding the comparison between the estimated and observed flow rates, the stepper motor produced excellent results.
Highlights
Variable rate sprinklers (VRS) for mechanical selfpropelled irrigation systems have been developed to promote localized water application in function of the spatio-temporal variability of irrigated areas in Precision Irrigation
Field tests were performed under different conditions of service pressure, rotation angles imposed on the pin and flow rate which resulted in maximal water throw radiuses ranging from 7.30 to 10.38 m
Young et al (2009) evaluated the Christiansen uniformity coefficient (CUc) of a variable rate sprinkler operated by a pulsing technique controlled by solenoids in a linear irrigation system
Summary
Variable rate sprinklers (VRS) for mechanical selfpropelled irrigation systems have been developed to promote localized water application in function of the spatio-temporal variability of irrigated areas in Precision Irrigation. Since the 1990’s, precision irrigation is being developed in response to the need to provide water to the soil in accordance with spatial variability of field topography, soil type, availability of water to the soil, production system and other factors, with the intent of optimizing production while conserving hydraulic resources and the environment (Stone et al, 2006). This is a new area of study, the variable flow irrigation systems should be more efficient in terms of operability and utilization of water and energy (Dukes and Perry, 2006). The authors reported uniformity values of 94.0, 94.8, 91.7 and 79.5 % for the applied irrigation depths of 25, 18, 13 and 6 mm, respectively
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