Drip fertigation is an effective method for enhancing water and fertilizer use efficiency. Filters, particularly disc filters, play a crucial role in preventing emitter clogging. However, fertilizers may influence disc filter performance. Thus, we evaluated the effects of three conventional fertilizers—urea (UR), diammonium phosphate (DAP) and potassium sulfate (PS)—mixed in different ratios on the performance of disc filters. According to potato drip fertigation practices, the mixed fertilizers were set to supply N, P₂O₅ and K₂O at mass ratios of 1:1:1 (T1), 1:0.3:0.7 (T2), and 1:0.7:0.3 (T3). A non-fertilized treatment (CK) was included as the control. Compared with CK, the mixed fertilizers accelerated the decline in disc filter performance. Head loss was 1.4–3.7 times higher, while relative flow rate and filtration efficiency were 81–91 % and 60–76 % of CK, respectively (p < 0.05). Both head loss and its growth rate were related to the PS:DAP ratio (p < 0.05). T2, with a ratio of 0.7:0.3, resulted in higher head loss (0.32–3.66 times) and its growth rate (0.36–5.26 times). Filtration efficiency was negatively related to the PS concentration (p < 0.05). In treatments with a high PS concentration (T1 and T2), filtration efficiency decreased by 16–40 %. The precipitation of salt, silt in deposited sediments, and the diversity of microbial communities in disc flow channels were related to the PS concentration (p < 0.05). PS emerged as a key factor affecting disc filter performance. Thus, it should be used minimally in drip fertigation practices.