Different Irrigation Pressure and Filter on Emitter Clogging in Drip Phosphate Fertigation Systems

Irrigation pressures and filters have a significant influence on emitter clogging in drip fertigation systems. Exploring the anti-clogging performance of emitters at different irrigation pressures (80, 90, 100 kPa; 40, 50, 60 kPa) and filters (the disc filter with an aperture of 125 μm, the screen filter with an aperture of 125μm, and the screen filter with an aperture of 200 μm) can provide suitable guidance for the design and operation of drip fertigation systems. The average relative discharge (Dra), the Christiansen uniformity coefficient (CU), and the differential pressure (DP) were analyzed to study the anti-clogging performance of flat emitters (FE) and labyrinth emitters (LE). Meanwhile, the scanning electron microscope and energy dispersive spectrometer were used to observe the surface morphology and chemical composition of clogging substances in filters and emitters. Results showed that the irrigation pressure of 90 and 50 kPa did not cause a significant decrease in Dra, and the Dra of two types of emitters were all great than 95.22%. When the irrigation pressure was 80 and 40 kPa, the Dra decreased significantly (73.48–78.71%, 81.3–83.6% for FE and LE). The CU values of emitters were all greater than 90% except for the irrigation pressures of 80 and 40 kPa. The relative Dra and CU of LE were greater than those of FE, indicating that the LE had a better anti-clogging performance compared with the FE. The decrease in DP reflected an increase in the emitter clogging degree. Meanwhile, irrigation pressures and the interaction between irrigation pressures and filters imposed a significant effect on the CU at a significance level of p < 0.05, p < 0.01, respectively. The clogging process was mainly affected by physical and chemical factors, and the generated clogging substances included phosphate fertilizer, silicate, carbonate, and phosphate precipitations. In conclusion, the best operation mode of phosphate fertilizer in drip fertigation systems was to use the disc filter with an aperture of 125 μm and the LE at the irrigation pressure of 50 kPa. An appropriate irrigation pressure combined with effective filters can reduce emitter clogging while saving water and fertilizer.