Effects of Potassium Fertilizer Sources on Emitter Clogging Characteristics and Hydraulic Performance in Brackish Water Drip Fertigation Systems

Brackish water drip fertigation has emerged as a promising approach for improving water use efficiency in saline agricultural regions where freshwater resources are limited. However, emitter clogging remains a critical challenge that compromises the long-term reliability and sustainability of these systems. Potassium fertilizers are widely applied through fertigation, yet the effects of different potassium sources on emitter clogging under brackish water conditions remain poorly understood. This study evaluated the impacts of five commonly used potassium fertilizers, including potassium dihydrogen phosphate (K1), potassium nitrate (K2), potassium chloride (K3), potassium sulfate (K4), and potassium tripolyphosphate (K5), on emitter hydraulic performance and clogging characteristics in a brackish water drip irrigation system. A 500 h fertigation experiment was conducted using six identical experimental platforms, one for each treatment, with three different types of non-pressure-compensating drip tape monitored within each platform. Changes in emitter performance were assessed using relative average discharge (Dra), Christiansen uniformity coefficient (CU), statistical uniformity coefficient (Us), and clogging randomness index. In addition, X-ray diffraction (XRD) analysis was employed to identify the mineral composition of accumulated clogging materials under different fertilizer treatments. Emitter performance differed among the potassium fertilizer formulations under the tested brackish-water conditions. Among the tested fertilizers, potassium sulfate (K4) maintained the most stable hydraulic performance, with a final Dra value of 83.62% ± 1.06%, whereas potassium chloride (K3) caused the greatest decline in emitter discharge, reducing Dra to 76.62% ± 1.05%. XRD analysis revealed that quartz and carbonate minerals were the dominant components of clogging deposits, although their relative proportions varied among fertilizer treatments. The differences in clogging development were closely associated with variations in mineral deposition patterns and hydraulic performance deterioration. Overall, potassium fertilizer selection plays an important role in maintaining the operational stability of brackish water drip fertigation systems. Under the tested brackish-water conditions, potassium sulfate showed the most stable hydraulic performance among the fertilizer treatments.