施肥对浑水灌溉滴头堵塞的加速作用

为探究水肥一体化灌溉过程中,施肥对滴头堵塞的影响,分别配置了4个施肥浓度(0,0.4,0.6和1.2 g/L),3种泥沙级配,进行浑水间歇灌水堵塞试验,并用场发射扫描电镜分析了堵塞物的结构与成分。结果表明:施肥对于迷宫滴头堵塞具有明显的加速作用,施肥浓度越大,加速堵塞效果越明显,当施肥1.2 g/L时,3种级配浑水的有效灌水次数比未施肥的对照处理分别下降了36.4%,77.8%和78.8%;当施肥0.4 g/L时,有效灌水次数分别下降9.1%、33.3%和14.3%,施肥浓度≤0.4 g/L时,加速滴头堵塞的效果较小。浑水中增加化肥增强了水体中泥沙颗粒间的絮凝作用,促进了稳定而致密团聚体的形成,这是施肥加速滴头堵塞的主要原因;施肥后堵塞物表面结构复杂程度增加,堆积体间隙减小,堵塞以完全堵塞为主。该试验结果为水肥一体化滴灌技术推广提供理论依据。

Accelerative effect of fertigation on emitter clogging by muddy water irrigation

Abstract: Integrated drip irrigation and fertilizer technology develops rapidly due to its advantages of high efficiency, water saving, ability to adapt to the terrain and so on, but fertilizer may cause the clogging of drip emitter, which draws much attention. In order to explore the influence of fertilizer on emitter clogging in the process of fertigation, a periodic intermittent experiment was carried out. Three particle gradations and four fertilizer concentrations (0, 0.4, 0.6, and 1.2 g/L) were desgined. The drip irrigation with fertilizer and muddy water of different particle gradations as conducted for 30 min each time under working pressure of 40 kPa. After 4 hours, the irrigation was redone. Then the relative flow rate of emitter and its uniformity were determined. After the experiment, the clogging positions of emitters were recorded. The drip tape was air-dried for 4 months for measurements of clogging status. The complete clogged emitters were used for observation by field emission scanning electron microscopy(FESEM) to analyze the structure and composition of the blockage. The results demonstrated that fertigation had an obvious acceleration effect on emitter clogging, and effect was more obvious in fertilizer solution with high concentration. When the application rate of fertilizer was 1.2 g/L, the effective irrigation times of muddy water with 3 different particle gradations decreased by 36.4%, 77.8% and 78.8% respectively; when the application rate of fertilizer was 0.4 g/L, the effective irrigation times of muddy water with 3 different particle gradations decreased by 9.1%, 33.3% and 14.3% respectively. The acceleration effect of fertilizer application on emitter was most non-obvious when the concentration of fertilizer solution was less than 0.4 g/L. The acceleration effect of fertilizer on emitter clogging was influenced by particle gradation. As for the drip tap selected in the test, the acceleration effect was more obvious in particles with dominated by 0.034-0.067 mm. Without fertilization, the particle gradation B with content of 0.034-0.067 mm particles higher than 50% was the easiest to cause clogging, followed by particle gradation A with content of 0-0.034 mm particles larger than 50%, and the particle gradation C with content of 0.067-0.1 mm particles larger than 50% was the least to cause clogging. Complete clogging was mainly in A and B particle gradation, while partial clogging was mainly in C. Fertilizer enhanced the flocculation of particles in muddy water and promoted the formation of stable and compact aggregates, which was the major cause of acceleration effect of emitter clogging. After fertigation, the surface structure of blockage was more complicated, the gap of aggregates decreased. Fertigation had little effects on clogging location and composition of blockage. The effect of fertilizer on clogging position and the main ingredient of the blockage were not obvious. After fertigation, the ratio of complete clogging to partial clogging in the 3 particle gradation increased. Compared to no fertilization, fertigation caused that the ratio of complete clogging to total clogging of emitters increased from 54% to 86.11%, and the ratio of complete clogging emitters to total tested emitters also increased from 26.67% to 34.44%. Fertigation did not change the gathering position of the blockage in emitters. The ratio of emitter import clogging to emitter channel clogging was 2.10 with fertigation, and 2.20 without fertigation. This research provides valuble information for the application and promotion of integrated drip irrigation and fertilizer technology.