From physical to coupled physical–chemical clogging: the role of nitrogen fertilizers in high-sediment water drip irrigation systems

• Fertilizer reshapes clogging mechanisms in high-sediment drip irrigation. • Clogging shifts from physical fouling to coupled physical–chemical fouling. • Urea and ammonium sulfate suppressed particle and carbonate deposition. • Calcium nitrate triggered massive calcite precipitation and severe clogging. • Fertilizer selection offers a practical strategy to mitigate emitter fouling. High-sediment water drip irrigation (HSWDIS) provides an important approach to alleviate water shortages in arid regions, yet emitter clogging remains the primary obstacle limiting its sustainable application. Previous studies have largely regarded clogging in HSWDIS as a process dominated by physical particle deposition, but the potential role of fertilizer application in reshaping fouling mechanisms has not been clarified. This study investigated the effects of three nitrogen fertilizers—ammonium sulfate (AS), calcium nitrate (CN), and urea (UR)—on emitter performance using an outdoor HSWDIS platform. Hydraulic measurements, deposit quantification, and mineralogical analyses were conducted to reveal how fertilizer type regulates clogging dynamics. The findings clearly demonstrate that fertilizer application not only alters the extent of fouling but also fundamentally reshapes the underlying mechanisms of emitter clogging. Fertigation drives a distinct transition from physical clogging dominated by sediment deposition to coupled physical–chemical fouling, in which suspended particles are strongly bound by fertilizer-induced precipitates, forming dense and complex composite deposits. Within this mechanistic framework, AS and UR effectively alleviated fouling by inhibiting particle aggregation and suppressing carbonate crystallization, whereas CN sharply aggravated clogging through massive calcite precipitation and particle encapsulation. These results provide the first systematic evidence that fertilizer type is a decisive factor in determining clogging pathways, and they highlight fertilizer selection as a practical and scalable strategy to mitigate fouling and extend the operational lifespan of sediment-laden drip irrigation systems. By clarifying how fertilizers transform clogging pathways, this study advances the mechanistic understanding of fouling processes and establishes a scientific basis for sustainable fertigation management in high-sediment water drip irrigation systems.