Optimizing the Fulvic Acid Potassium to Inorganic Fertilizer Ratio Mitigates Disc Filter Clogging in Drip Fertigation

ABSTRACT The combined application of organic and inorganic fertilizers (COIF) is a well‐established practice in drip fertigation, but its impact on the disc filter—an important and widely used engineering component that serves as the primary defence against emitter clogging—remains unclear. This study investigated disc filter performance under different mixing ratios of fulvic acid potassium (FAK) and inorganic fertilizers (urea, potassium sulfate and diammonium phosphate). The evaluation encompassed both hydraulic performance indicators—including head loss, relative flow rate, head loss growth rate and relative flow rate decline rate—and filtration performance indicators, such as post‐filtration sediment concentration and filtration efficiency. The results showed that the organic–inorganic fertilizer ratio significantly influenced disc filter performance ( p < 0.05). With increasing FAK proportion (0%–70%), head loss first decreased and then increased, whereas flow capacity and filtration efficiency first increased and then declined. In this study, replacing 48% of inorganic fertilizer with FAK reduced head loss by 28%–80%, increased the relative flow rate by 3%–34%, enhanced filtration efficiency by 17%–125% and extended the effective irrigation duration of emitters by 25%–233% compared with other ratios. To ensure the long‐term reliable operation of COIF drip irrigation systems, the FAK substitution ratio should be controlled and not excessively high.