Effects of Urea Fertigation on Emitter Clogging in Drip Irrigation System with Muddy Water

In this study, 10 test cycles of fertigation with urea using muddy water were performed to examine the anticlogging performance of inline nonpressure-compensating emitters. The potential causes of emitter blockage were proposed from the adsorption behavior of urea on sediments, the morphology and components of the clogging materials, and the total number of microorganisms. The results showed that drip irrigation (DI) with muddy water led to the sedimentation of various minerals (e.g., illite, montmorillonite, calcite, and quartz) in the clogging materials and accelerated the risk of emitter clogging. The weak adsorption of urea (7.4% at an equilibrium time of 6 h and a pH value of 7.9) exhibited a negligible effect on the flocculation, agglomeration, and settlement of sediment particles. The addition of 2% urea inhibited the number of bacteria and fungi in the lateral sediment and induced a 1,000-fold increase in the total number of actinomycetes. The discharge reduction rate (Drr) of emitters exhibited a high correlation (r=0.9892; p<0.01) with the dry weight (DW) of solid particles. The clogging mechanisms of emitters with urea muddy water fertigation were the result of the agglomeration of solid particles via the crosslinking of actinomycete secretions and the precipitation of calcite phase (CaCO3). These research findings can serve as an essential scientific basis for selecting proper management strategies of urea muddy water fertigation in the Yellow River irrigation area. (c) 2019 American Society of Civil Engineers.