Effect of magnetization of irrigation water on the clogging of drip irrigation emitters with integrated water and fertilizer

Abstract: This study aims to explore the effect of magnetization treatment on the clogging of drippers for the integrated drip irrigation of water and fertilizer in the area of the Yellow River. Taking the inner-embedded drip emitter as the research object, the intensity of magnetization was set to 0.2, 0.4, and 0.6 T, where the control group was unmagnetized. A short-term intermittent irrigation test was also carried out for 2% of the mass of potassium sulfate fertilizer, urea, and compound fertilizer muddy water (sediment content of 3.0 g/L). The results showed that the magnetization significantly slowed down the downward trend of dripper flow and irrigation uniformity (P<0.01). The optimal magnetization intensity greatly varied in the different fertilizers. Specifically, there was the greatest mitigation effect of dripper flow for the mixture of potassium sulfate fertilizer and compound fertilizer, when the magnetization intensity was 0.4T. The greatest mitigation effect was found during the decrease in the flow rate of the dripper in the urea mixture at the magnetization intensity of 0.2 T. The effective irrigation times for the mixture of potassium sulfate fertilizer, urea, and compound fertilizer without magnetization treatment (irrigation times with a relative flow rate greater than 75%) were 10, 10, and 3 times, respectively. Furthermore, the effective irrigation times of different fertilizer mixtures increased after the magnetization treatment. When the magnetization intensity was 0.4, 0.2, and 0.4 T, the effective irrigation times of potassium sulfate fertilizer, urea, and compound fertilizer mixture increased the most, which were 16, 15, and 7 times, respectively. The number of clogged emitters increased significantly in the front section of the capillary tube for the potassium sulfate fertilizer and compound fertilizer treatment, whereas, the urea decreased after magnetizing the irrigation water. In the 0.4 T treatment, the most increased number of blocked drippers was found in the front section of the capillary for the potassium sulfate fertilizer and compound fertilizer mixture, which were 68.77% and 27.50%, respectively. In the 0.2 T treatment, there was the largest decrease (55.36%) in the number of blocked drippers in the front section of the urea mixed liquid capillary tube. The ratio for the amount of sediment in the capillary tube to the amount of sediment output from the dripper was represented by η under different magnetization treatments. When applying potassium sulfate fertilizer and compound fertilizer, the magnetization treatment increased the value of η, indicating the largest increase at 0.4 T. By contrast, the magnetization treatment reduced the value of η, when the urea was applied, indicating the most obvious decrease at 0.2 T. As such, the magnetization significantly dominated the sedimentation and movement for the sensitive particle size of emitter blockages. Specifically, the magnetization significantly increased the proportion of sensitive particle size (smaller than 0.03 mm) in the siltation sediment for the capillary of the potassium sulfate and the compound fertilizer mixture, reducing the proportion of sensitive particle size in the sediment output from the emitter, where that of urea was the opposite. When the magnetization intensity was 0.4 T, after applying potassium sulfate fertilizer and compound fertilizer, the sediment-sensitive particle size in the front and middle of the capillary increased the most: 25.75%, 11.17%, and 17.87%, 10.36%, respectively. After applying urea, the magnetization presented the largest decrease, when the magnetization was 0.2 T. When the magnetization intensity was 0.4 T, the proportion of sensitive particle size in the output sediment of the potassium sulfate and the compound fertilizer mixture dripper presented the largest decrease, which was 5.33% and 4.61%, respectively. When the magnetization intensity was 0.2 T, the urea mixed liquid dripper presented the largest increase in the proportion of sensitive particle size in the sediment output, which was 5.26%. The finding can provide a strong reference for the anti-clogging prevention measures in the drip irrigation drippers with integrated water and fertilizer in the Yellow River irrigation areas.