Investigating the simultaneous effect of irrigation water temperature and pressure on discharge of Irrigation drip tapes of seaming and plaque equipped

Background and objectives: The performance of drip tape irrigation system depends on the choice of irrigation tape and its hydraulics. Numerous factors affect the discharge of the drip tape irrigation, the most important of which are the changes in pressure and temperature of the irrigation water. Changes in field topography, unsuitable design of the irrigation system, as well as the use of tapes with long length, cause a pressure difference between the drippers of the irrigation tapes. Also, the water temperature of the laterals pipes exposed to direct sunlight increases significantly. In some studies, the effect of increasing or decreasing water temperature on the discharge of tapes of drip irrigation has been studied, but in this study, the effect of water temperature in different operating pressures on the two types of drip irrigation tapes of seaming and plaque equipped has been studied and was attempted to present the results as applied equations and compared.
Materials and methods: In this study, 10 types of drip irrigation tapes were selected from two types of seaming and plaque equipped with the codes ID, I, T1, T2, T3, T4, B, S, P, and YD. In each tape were selected 25 test sample, randomly, which every test sample included at least 3 dripper units. The length of each test sample was in the range of 100 to 120 cm. In order to investigate the simultaneous effect of pressure and irrigation water temperature on the discharge of irrigation tapes, a physical model was designed and built in the Research Laboratory of Water Science and Engineering, University of Kurdistan in 2018.4 different irrigation water temperatures, including 13, 23, 33, and 43 centigrade, were applied to the irrigation tapes at operating pressures of 1 meter to 1.2 times the maximum pressure. All tests were performed according to ISO 9261 and IRISI 6775. General Equations of discharge - Pressure and normalized discharge - Temperature, all tapes were obtained. In order to investigate the effect of temperature on the discharge of irrigation tapes, an experiment was conducted in a completely randomized design with 4 treatments and 25 replications. Experimental treatments included 4 different temperatures (13, 23, 33 and 43 ° C). Data were analyzed by SAS statistical software and the mean of treatments was compared using LSD test.
Results: At the standard temperature of 23 ° C, the power of the discharge -pressure equation of 6 tapes was less than 0.5, 2 tapes between 0.5 to 0.6 and 2 tapes between 0.6 to 0.8. Therefore, all tapes were pressure non - compensating and their flexibility in terms of pressure changes was desirable and acceptable. At other temperatures studied, the power of discharge -pressure equation changed, which was less than 0.8 in all cases. The effect of temperature on the discharge of all irrigation tapes was significant (p < 0.05) and often increased with increasing temperature. The power of linear equation of normalized discharge -temperature of the tapes ranged from 0.02 to 0.66 and the width of their origin was between 53 and 121. The sensitivity of plaque equipped drip irrigation tapes to temperature changes was lower than seaming drip irrigation tapes and had lower discharge changes.
Conclusion: All of the drip irrigation tapes studied are of good quality in terms of sensitivity to pressure changes. Also, due to the fact that increasing the temperature of irrigation water increases the discharge of the tapes, it is recommended to use the plaque equipped tapes and normalized discharge equations proposed by the present study in areas where the changes in irrigation water temperature are between 13 to 43 ° C.