Emitter clogging is one of the most significant obstacles to the widespread adoption of subsurface drip irrigation (SDI). This research focused on a five-year-old corn SDI system operating in the North China Plain, where the flow rates and internal clogging material content of 3384 non-pressure compensation emitters (accounting for 51.2 % of the total number of emitters) were measured through excavation. This research explored the response patterns of the emitter relative discharge (Dra), Christiansen uniformity coefficient (Cu), flow index (x), and clogging substance content in various parts of the emitters to different levels of irrigation, nitrogen application, and aeration. The results revealed that Dra and Cu significantly decreased (p < 0.05) with increasing nitrogen application, whereas the changes in irrigation and aeration were not statistically significant. The average Dra and Cu for the entire system were 88.3 % and 91.2 %, respectively, indicating good uniformity of the water distribution in the SDI system. The average x of the emitters increased from 0.47 before installation to 0.53, suggesting a transition from turbulent flow to a partially turbulent flow state, which increased the risk of emitter clogging. Both Dra and Cu decreased linearly with increasing x (R2=0.64–0.78). The proportions of clogging substances in the emitter flow channels (mc), outlet (mo), and intrusion root (mr) dry weight were 28.9 %, 69.3 %, and 1.8 % of the total clogging substance dry weight (M), respectively. The particle size distributions of the clogging substances at the outlets were similar to those of the surrounding soil, which was caused mainly by negative pressure suction. Root intrusions were mostly concentrated at the outlets, with a small portion entering the flow channels, accounting for 4.3–20.1 % of the total flow channel length. Owing to the well-designed pressure regulation and air exhaust system used in this SDI research, along with higher soil moisture in the crop root zone, the negative linear relationship between Dra and mc was most significant (p < 0.01). Based on time projection, this SDI system could operate normally for 8–11 years (Dra, Cu ≥ 80 %). To achieve a life of more than 20 years, additional acid/chlorine treatments, which supplement the existing system components and the current practice of flushing twice annually, are necessary.

中文翻译：

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华北平原地下滴灌系统运行五年的水力性能和堵塞特性


喷头堵塞是广泛采用地下滴灌 （SDI） 的最重要障碍之一。本研究的重点是在华北平原运行的 5 年历史的玉米 SDI 系统，该系统通过挖掘测量了 3384 个非压力补偿发射器（占发射器总数的 51.2%）的流量和内部堵塞材料含量。本研究探讨了发射器相对流量 （Dra）、Christiansen 均匀系数 （Cu）、流动指数 （x） 和发射器各个部分的堵塞物质含量对不同灌溉、施氮和曝气水平的响应模式。结果表明，随着施氮量的增加，Dra 和 Cu 显著降低 （p < 0.05），而灌溉和通气的变化无统计学意义。整个系统的平均 Dra 和 Cu 分别为 88.3 % 和 91.2 %，表明 SDI 系统中水分分布具有良好的均匀性。发射器的平均 x 从安装前的 0.47 增加到 0.53，这表明从湍流过渡到部分湍流状态，这增加了发射器堵塞的风险。Dra 和 Cu 均随 x 的增加线性降低 （R2=0.64–0.78）。发源流道 （mc）、出口 （mo） 和侵入根 （mr） 干重中堵塞物质的比例分别为总堵塞物质干重 （M） 的 28.9 %、69.3 % 和 1.8 %。出口处堵塞物质的粒径分布与周围土壤相似，主要由负压吸力引起。 根系侵入主要集中在出口处，一小部分进入流道，占流道总长度的 4.3–20.1 %。由于本次 SDI 研究中使用的精心设计的压力调节和排气系统，以及作物根区土壤水分较高，Dra 和 mc 之间的负线性关系最为显着 （p < 0.01）。根据时间预测，该 SDI 系统可以正常运行 8-11 年 （Dra、Cu ≥ 80%）。为了实现 20 年以上的使用寿命，需要额外的酸/氯处理，以补充现有的系统组件和目前每年冲洗两次的做法。