Effect of manganese and copper concentrations on emitter clogging in brackish water drip irrigation systems

The use of brackish water in drip irrigation has proven to be an effective strategy for alleviating water scarcity in arid regions. However, the problem of emitter clogging remains a major barrier to the widespread adoption of this technology. The application of manganese (Mn) and copper (Cu) offers a promising dual benefit: mitigating emitter clogging while simultaneously supplying essential trace element fertilizers. Nevertheless, the optimal concentrations of Mn and Cu for this purpose remain unclear. This study investigated the effects of seven different manganese ion (Mn^2 +) concentrations (0–3.0 mg/L) and seven different copper ion (Cu²⁺) concentrations (0–0.3 mg/L) on emitter clogging in brackish water drip irrigation systems. The results demonstrate that emitter clogging in brackish water drip irrigation systems can be effectively mitigated by regulating Mn²⁺ and Cu²⁺ concentrations. As concentrations of Mn²⁺ and Cu²⁺ increased, the dry weight of emitter clogging substances initially increased and then decreased. Compared to water sources without ion addition, Mn²⁺ concentrations of 0–1.5 mg/L exacerbated emitter clogging, while concentrations of 1.5–3.0 mg/L mitigated it. This was due to 0–1.5 mg/L promoting the formation of clogging substances calcite and Na-feldspar, whereas 1.5–3.0 mg/L reduced the formation of substances quartz, muscovite, and chlorite. Conversely, Cu²⁺ concentrations of 0–0.3 mg/L reduced the fouling accumulation process, with the optimal emitter clogging control observed at 0.3 mg/L. This was attributed to Cu²⁺ reducing the formation of substances quartz and calcite. Based on the findings, it is recommended that Mn²⁺ concentrations be maintained above 2.0 mg/L and Cu²⁺ concentrations no less than 0.15 mg/L in drip irrigation systems. These results provide practical guidance for emitter clogging control and contribute to the sustainable utilization of brackish water resources in agriculture.