TY - JOUR
AU - Yang, Wenxin
AB - 1. Introduction Water scarcity is a critical challenge for global agriculture, especially in arid and semi-arid regions, where it limits economic growth and crop production. Drip irrigation, recognized for its water efficiency and precision in nutrient delivery, has become an essential technology in addressing these challenges [1, 2]. However, clogging of drip irrigation systems, often caused by sediment content and particle size, remains a significant issue that adversely affects system performance and longevity [3, 4]. Factors such as laying slope, working pressure, and manufacturing deviations further influence the hydraulic performance and susceptibility to clogging of the drip irrigation tapes [5, 6]. Dripper clogging has always been a focal point of research [7, 8]. Preventing dripper clogging of drip irrigation tape and improving irrigation efficiency are the key issues of their research focus. Currently, the main methods for clogging treatment include pretreatment and timely cleaning of the drip irrigation tapes and filters [9]. The clogging of drip irrigation tapes can be roughly classified as physical clogging, chemical clogging, and biological clogging. Nakayama also assessed the water quality due to clogging of dripper and proposed a water quality classification table for clogging of irrigators [7]. Water quality is the most fundamental cause of dripper clogging, and it has a significant influence on the hydraulic performance of the drip irrigation tape. Adin et al. conducted a drip irrigation experiment with sewage water to study the clogging of the dripper and found that the form of the flow channel of the dripper had a significant influence on the clogging performance [10]. Xu et al. verified the numerical simulation results by using short-period scale inhibition experiments, and revealed the relationship between the hydraulic performance and anti-clogging performance of the dripper [11]. Qiu et al. used physical experiments and numerical simulations to explore the effects of different tooth shape designs on dripper flow characteristics and anti-clogging performance, and pointed out that the BUV (teeth are perpendicular to the upstream vertical surface) flow channel has the best improvement effect on the anti-clogging performance of the dripper [12]. Zhou et al. used three kinds of inferior water to carry out drip irrigation tape clogging test to determine the anti-clogging ability of different drippers, and determined the parameters that can be directly used to evaluate the anti-clogging ability of drippers [13]. Wang et al conducted an in-situ field study to investigate the impacts of saline water concentrations and water-soluble P-fertilizer types on DI system performance, and explored the dynamic variation of chemical precipitations accumulated in drip irrigation drippers [14]. Zhang et al. selected four different water salinities to conduct an on-site drip irrigation experiment in Hetao Irrigation District, and analysed the behavior and dripper distribution of chemical clogging in a drip irrigation system [15]. Li et al. conducted a drip irrigation experiment with four irrigation and flushing treatments to study the chemical precipitates dynamic variations in the clogging substances, and reveal the mechanism of chemical precipitates and their impacts on the clogging process [16]. Under muddy-water conditions, the form of the flow channel exerts a significant influence on dripper clogging. Additionally, factors such as fertilizer concentration, sediment content, and working pressure also play crucial roles in this process. Although the current water and fertilizer integrated drip irrigation technology is gradually being popularized, the problem of dripper clogging has been further aggravated. Li et al. demonstrated that fertilization significantly exacerbates dripper clogging by inducing the aggregation of sediment particles [17]. Wang et al. conducted a study and found that large amounts of carbonate sediments and fertilizers are the most important reasons for the severe clogging of drip irrigation systems [18]. Liu et al. found that different types of fertilizers have significant influences on the clogging of the dripper [19]. Dripper clogging is a multifaceted problem influenced by various factors, yet most studies have focused on single-factor effects. This study addresses the gap by employing a uniform orthogonal test to examine the combined impact of fertilizer concentration, sediment content, and working pressure on the average relative flow in single-winged labyrinth drip irrigation tapes. Through range analysis, variance analysis, and multiple analysis of main effects, we ranked the significance of these factors and explored their interactions. Our findings establish critical relationships between clogging factors and flow performance, providing essential insights for optimizing water-fertilizer integrated irrigation systems. 2. Materials and methods 2.1. Test materials and equipment In this study, the single-wing labyrinth drip irrigation tapes with flows of 1.8, 2.6, and 3.2 L/h produced by Xinjiang Tianye Water Saving Irrigation Co., Ltd. were selected. The hydraulic performance parameters of the drip irrigation tapes are shown in Table 1. The size parameters of these tapes are shown in Fig 1. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 1. Photograph of drip irrigation tape. https://doi.org/10.1371/journal.pone.0313888.g001 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 1. Hydraulic performance parameters of the drip irrigation tapes. https://doi.org/10.1371/journal.pone.0313888.t001 The fertilizer used in the experiment was manufactured by Jiashili(Yingcheng) Chemical Fertilizer Co., Ltd. The most commonly used potassium-sulphate-type compound fertilizer was chosen, which has high water solubility, easy absorption characteristics, high nutrient contents, few auxiliary components, and with good physical properties. The proportion of nutrients N:P2O5:K2O was 1: 1: 1, and the total nutrient content was ≥51%. The silt was natural loess from Xishan Mountain in Urumqi, and it was sieved through using a 120-mesh sieve. First, a set of standard sieves was used to sieve the particles with diameters larger than 0.074 mm, the material in each sieve was collected, and the particles were weighed to obtain the percentage of the soil weight. If the particle size was less than 0.074 mm, a certain amount of soil suspension with a uniform concentration was prepared with a graduated cylinder. The suspension densities at different times were measured, and the weight percentage of particles in the soil was calculated based on the densitometer reading and the soil particle settling time. Finally, the distribution curve of the particle size was obtained, as shown in Fig 2. It can be seen that 100% of the particles had particle sizes smaller than 0.125 mm, 35.28% were smaller than 0.1 mm, and the median particle size (D50) was 0.106 mm. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 2. Sediment particle size curve. https://doi.org/10.1371/journal.pone.0313888.g002 The schematic diagram of the device is shown in Fig 3. This drip irrigation tape anti-clogging performance test bench was a KD-DJC, which was manufactured by Hebei Kedao Testing Machine Technology Co., Ltd., and the system was suitable for a voltage of 380 V. The main control cabinet included a Xilin SD 200 vector inverter. The frequency range of the device is between 0–600 Hz, the load frequency range was between 2–10 kHz, and the speed regulation range was 1:50 or 1 Hz/150% rated torque. A 32 CDLF4-150 light multi-stage pump, produced by Yongjia Yingke Pump Valve Co., Ltd., was used for water injection. The flow was 4 m3/h, the pump speed was 2880 r/min, the lift was 120 m, and the power was 3 kW. A YE2-802-2 three-phase asynchronous motor was used to provide 11 kW of powder. The voltage was 380 V, the frequency was 50 Hz, and the rotation speed was 2830 r/min. An IRK 50–100 centrifugal pump was used with a flow of 22.3 m3/h, lift of 10 m, matching power of 1.1 kW, and rotation speed of 2900 r/min. The electronic balance model used in this study is the YP2002 N, manufactured by Shanghai Jinghai Instrument Co., Ltd., with a maximum range of 2000 g and an accuracy of 0.01 g. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 3. Schematic diagram of the test platform for anti-clogging performance of drip irrigation tape (pipe). https://doi.org/10.1371/journal.pone.0313888.g003 The length of the drip irrigation tape test platform is 35 m, and a total of 3 drip irrigation tapes are laid. Each drip irrigation tape is equipped with 25 water collection buckets, with total of 75 water collection buckets. The dripper flow was measured by weighing method. Measurements were made every 15 minutes, and record the average of three readings per measurement. In the test, under the premise of fixed laying length (35m) and slope (0%), the three factors of sediment content, fertilizer concentration and working pressure were used as the selection factors. Three levels were selected for each factor, and the specific factor levels were shown in Table 2. The uniform orthogonal design table UL9 (33) was used to design the test scheme. The specific design is shown in Table 3. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 2. Factors and levels. https://doi.org/10.1371/journal.pone.0313888.t002 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 3. Uniform orthogonal test UL9(33). https://doi.org/10.1371/journal.pone.0313888.t003 To expedite the experiment and broaden the model’s prediction interval, we selected irrigation water with suspended solids concentrations exceeding the farmland irrigation water quality standard by more than tenfold, by using a mass concentration of ≤ 0.1 g/L as the baseline. The sediment concentrations were set at 1, 2, and 3 g/L. To better simulate actual irrigation conditions and ensure that sediment particles fully collide, coagulate, and deposit within the flow channels, both the irrigation duration and intervals were extended within feasible limits. Irrigation was conducted in 10-minute cycles with 30-minute intervals. A total of 9 irrigation cycles were conducted, with flows measured after each cycle. After each treatment, new drip irrigation tapes were installed, and the system components, including pipes, water tanks, and pumps, were thoroughly flushed. 2.2. Evaluation index In this test, the average relative flow was used as the evaluation index to assess clogging in the drip irrigation tape. Clogging was determined based on whether the average relative flow fell below 0.75 (GB/T19812.3–2017). The formula of the average relative flow is as follows: (1) where q is the average relative flow, i is the drop number, N is the total number of drops, qpi is the muddy-water flow of the ith dripper (L/h), and qi is the water flow of the ith dripper (L/h). 2.1. Test materials and equipment In this study, the single-wing labyrinth drip irrigation tapes with flows of 1.8, 2.6, and 3.2 L/h produced by Xinjiang Tianye Water Saving Irrigation Co., Ltd. were selected. The hydraulic performance parameters of the drip irrigation tapes are shown in Table 1. The size parameters of these tapes are shown in Fig 1. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 1. Photograph of drip irrigation tape. https://doi.org/10.1371/journal.pone.0313888.g001 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 1. Hydraulic performance parameters of the drip irrigation tapes. https://doi.org/10.1371/journal.pone.0313888.t001 The fertilizer used in the experiment was manufactured by Jiashili(Yingcheng) Chemical Fertilizer Co., Ltd. The most commonly used potassium-sulphate-type compound fertilizer was chosen, which has high water solubility, easy absorption characteristics, high nutrient contents, few auxiliary components, and with good physical properties. The proportion of nutrients N:P2O5:K2O was 1: 1: 1, and the total nutrient content was ≥51%. The silt was natural loess from Xishan Mountain in Urumqi, and it was sieved through using a 120-mesh sieve. First, a set of standard sieves was used to sieve the particles with diameters larger than 0.074 mm, the material in each sieve was collected, and the particles were weighed to obtain the percentage of the soil weight. If the particle size was less than 0.074 mm, a certain amount of soil suspension with a uniform concentration was prepared with a graduated cylinder. The suspension densities at different times were measured, and the weight percentage of particles in the soil was calculated based on the densitometer reading and the soil particle settling time. Finally, the distribution curve of the particle size was obtained, as shown in Fig 2. It can be seen that 100% of the particles had particle sizes smaller than 0.125 mm, 35.28% were smaller than 0.1 mm, and the median particle size (D50) was 0.106 mm. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 2. Sediment particle size curve. https://doi.org/10.1371/journal.pone.0313888.g002 The schematic diagram of the device is shown in Fig 3. This drip irrigation tape anti-clogging performance test bench was a KD-DJC, which was manufactured by Hebei Kedao Testing Machine Technology Co., Ltd., and the system was suitable for a voltage of 380 V. The main control cabinet included a Xilin SD 200 vector inverter. The frequency range of the device is between 0–600 Hz, the load frequency range was between 2–10 kHz, and the speed regulation range was 1:50 or 1 Hz/150% rated torque. A 32 CDLF4-150 light multi-stage pump, produced by Yongjia Yingke Pump Valve Co., Ltd., was used for water injection. The flow was 4 m3/h, the pump speed was 2880 r/min, the lift was 120 m, and the power was 3 kW. A YE2-802-2 three-phase asynchronous motor was used to provide 11 kW of powder. The voltage was 380 V, the frequency was 50 Hz, and the rotation speed was 2830 r/min. An IRK 50–100 centrifugal pump was used with a flow of 22.3 m3/h, lift of 10 m, matching power of 1.1 kW, and rotation speed of 2900 r/min. The electronic balance model used in this study is the YP2002 N, manufactured by Shanghai Jinghai Instrument Co., Ltd., with a maximum range of 2000 g and an accuracy of 0.01 g. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 3. Schematic diagram of the test platform for anti-clogging performance of drip irrigation tape (pipe). https://doi.org/10.1371/journal.pone.0313888.g003 The length of the drip irrigation tape test platform is 35 m, and a total of 3 drip irrigation tapes are laid. Each drip irrigation tape is equipped with 25 water collection buckets, with total of 75 water collection buckets. The dripper flow was measured by weighing method. Measurements were made every 15 minutes, and record the average of three readings per measurement. In the test, under the premise of fixed laying length (35m) and slope (0%), the three factors of sediment content, fertilizer concentration and working pressure were used as the selection factors. Three levels were selected for each factor, and the specific factor levels were shown in Table 2. The uniform orthogonal design table UL9 (33) was used to design the test scheme. The specific design is shown in Table 3. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 2. Factors and levels. https://doi.org/10.1371/journal.pone.0313888.t002 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 3. Uniform orthogonal test UL9(33). https://doi.org/10.1371/journal.pone.0313888.t003 To expedite the experiment and broaden the model’s prediction interval, we selected irrigation water with suspended solids concentrations exceeding the farmland irrigation water quality standard by more than tenfold, by using a mass concentration of ≤ 0.1 g/L as the baseline. The sediment concentrations were set at 1, 2, and 3 g/L. To better simulate actual irrigation conditions and ensure that sediment particles fully collide, coagulate, and deposit within the flow channels, both the irrigation duration and intervals were extended within feasible limits. Irrigation was conducted in 10-minute cycles with 30-minute intervals. A total of 9 irrigation cycles were conducted, with flows measured after each cycle. After each treatment, new drip irrigation tapes were installed, and the system components, including pipes, water tanks, and pumps, were thoroughly flushed. 2.2. Evaluation index In this test, the average relative flow was used as the evaluation index to assess clogging in the drip irrigation tape. Clogging was determined based on whether the average relative flow fell below 0.75 (GB/T19812.3–2017). The formula of the average relative flow is as follows: (1) where q is the average relative flow, i is the drop number, N is the total number of drops, qpi is the muddy-water flow of the ith dripper (L/h), and qi is the water flow of the ith dripper (L/h). 3. Results and analysis Combined with the data, the effects of working pressure (B), sediment content (F) and fertilizer concentration (E) on the average relative flows under the condition of drip irrigation with muddy-water (irrigation tape length is 35 m, slope is 0%) were analysed. The influences of these factors on the average relative flow of the single-wing labyrinth drip irrigation tapes were examined, the order of the influence of these factors on the average relative flow was determined, and the relationships between the factors affecting the clogging and the average relative flow were established. The relationship between the relative flow and the optimal operating conditions in this case were explored. 3.1. Analyse the test results under muddy-water conditions using SPSS software The range analysis and multiple comparison analysis of the main effects were carried out on the measurements under muddy-water to explore the relationship between each factor and the test index, then to determine the effects of the working pressure (B), sediment content (F), and fertilizer concentration (E). The order of importance of the influence factors on the average relative flow of the single-wing labyrinth drip irrigation tape was determined. 3.2. Test results The tests were carried out based on an orthogonal experiments scheme, and the average relative flow under muddy-water condition was calculated using formula (1). The results are shown in Table 4. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 4. UL9(33) uniform orthogonal design and test results. https://doi.org/10.1371/journal.pone.0313888.t004 3.3. Range analysis Tables 5, 6 and 7 show the range analysis results of the average relative flow for different values of the test factors in the H1, H2, and H3 single-wing labyrinth drip irrigation tapes. The order of the influence factors (laying pressure (B), sediment content (F), and fertilizer concentration (E)) on the average relative flow of the single-wing labyrinth drip irrigation tape under muddy-water conditions for the H1, H2, and H3 single-wing labyrinth drip irrigation tapes was as follows: RF > RE > RB > RD. The order of the factors affecting the average relative flow of the drip irrigation tape was as follows: F(sediment content) > E(fertilizer concentration) > B(working pressure). Download: PPT PowerPoint slide PNG larger image TIFF original image Table 5. Results of the range analysis of each factor (H1). https://doi.org/10.1371/journal.pone.0313888.t005 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 6. Results of the range analysis of each factor (H2). https://doi.org/10.1371/journal.pone.0313888.t006 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 7. Results of the range analysis of each factor (H3). https://doi.org/10.1371/journal.pone.0313888.t007 The relevant factor indicators are shown in Fig 4. As shown in Fig 4(A), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1 g/L, and working pressure is 40 kPa in the type-H1 single-wing labyrinth drip irrigation tape. As for Fig 4(B), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1g/L, and working pressure is 40 kPa in the type-H2 single-wing labyrinth drip irrigation tape. As for Fig 4(C), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1g/L, and working pressure is 70 kPa in the type-H3 single-wing labyrinth drip irrigation tape. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 4. Average relative flow of drip irrigation tape with different factor values: (a) drip irrigation tape type H1, (b) drip irrigation tape type H2, and (c) drip irrigation tape type H3. https://doi.org/10.1371/journal.pone.0313888.g004 3.4. Variance analysis and multiple comparison analysis of principal effects 3.4.1. Variance analysis. The results of the variance analysis are shown in Table 8. At the 95% probability level, the results showed that the fertilizer concentration and sediment concentration of the type-H1 drip irrigation tape reached the extremely significant level (p < 0.01). For the type-H2 and type-H3 drip irrigation tapes, the sediment concentration reached the extremely significant level, and the fertilizer concentration reached the significant level (p < 0.05). The effects of the working pressure on the relative flows of the three drip irrigation tapes did not reach the significant level. This showed that the fertilizer concentration and the sediment concentration had significant impacts on the relative flows of the drip irrigation tapes, and thus, they would be important factors causing the dripper to clog. The fertilizer concentration of the type-H1 drip irrigation tape reached the extremely significant level, while for the type-H2 and type-H3 drip irrigation tapes, it only reached the significant level. All three types of drip irrigation tapes were single-wing labyrinth flow channels, but the type-H1 drip irrigation tape was relatively narrower than the type-H2 and type-H3 drip irrigation tapes. To a certain extent, this narrow tape enhanced the collision and flocculation of sediment particles after fertilization, making it easier to form a stable agglomeration mechanism to clog the dripper. From the F values, it can be seen that the order of the factors affecting the average relative flow of the three single-wing labyrinth drip irrigation tapes was F > E > B, that is, sediment content > fertilizer concentration > working pressure, and the variance analysis results were consistent with the range analysis results. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 8. Variance analysis of average relative flow. https://doi.org/10.1371/journal.pone.0313888.t008 3.4.2. Multiple comparison analysis of principal effects. SPSS 22.0 was used to analyse the differences between different levels of the influence factors. The range analysis showed that the influence of the working pressure (B) was not significant, so multiple comparison analysis regarding to working pressure (B) was not conducted. The multiple comparison results of the principal effects are shown in Table 9. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 9. Multiple comparison analysis of principal effects. https://doi.org/10.1371/journal.pone.0313888.t009 The comparison of fertilizer concentration (E) and sediment content (F) across different drip irrigation tapes highlights several significant trends in the average relative flows. For the H1 drip irrigation tape, under different fertilizer concentration treatments, the highest average relative flow was observed in the E1 treatment (0.670), which was significantly higher than both E2 and E3 treatments. This indicates that higher fertilizer concentrations, like in the E1 treatment, may enhance the flow stability in this particular tape. Similarly, the sediment content in the H1 drip irrigation tape had a pronounced effect on the flow, with the F1 treatment showing the highest average relative flow (0.699). This suggests that lower sediment content positively impacts flow performance, as all comparisons between F1, F2, and F3 were statistically significant. In the H2 drip irrigation tape, the results were somewhat different. While the E1 treatment again produced the highest flow (0.618), the difference between the E2 and E3 treatments was not significant. This could imply that H2 tapes are less sensitive to variations in fertilizer concentration beyond a certain point. Regarding sediment content, the F1 treatment consistently showed a higher average relative flow (0.681) than the other sediment content treatments, reinforcing the idea that cleaner water conditions improve irrigation efficiency in these systems. For the H3 drip irrigation tape, the average relative flow of the F1 treatment was highest (0.698), and there was a significant 12.1% decrease in flow from F1 to F3. This pattern, observed across all treatments, suggests a strong inverse relationship between sediment content and flow performance in the H3 tape. Additionally, in terms of fertilizer concentration, the E1 treatment (0.668) had the highest relative flow, with significant differences noted across all treatments, indicating that both fertilizer concentration and sediment content substantially influence the performance of the H3 tape. 3.5. Analysis of influences of different working conditions on average relative flow It can be seen from the previous analysis that the working pressure had no significant effect on the clogging of the dripper in muddy-water condition. Therefore, only the effects of the sediment concentration and fertilizer concentration on the clogging of the dripper are discussed in this section. Fig 5(A)–5(I) show the average relative flow of the H1-type, H2-type, and H3-type drip irrigation tapes under different working pressures of 40, 70, and 100 kPa, respectively. The notation "1–0.6" represents working conditions with a sediment content of 1 g/L and a fertilizer concentration of 0.6 g/L. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 5. Changes in average relative flow under different conditions. Note: (a)–(c) show the average relative flow rate of H1-type drip irrigation tape under working pressures of 40 kPa, 70 kPa, and 100 kPa, respectively, under different sediment content and fertilizer concentration conditions. (d)–(f) show the performance of H2-type drip irrigation tape under the same pressure conditions, while (g)–(i) display the performance of H3-type drip irrigation tape. (’1–0.6’ represents a sediment content of 1 g/L and a fertilizer concentration of 0.6 g/L). https://doi.org/10.1371/journal.pone.0313888.g005 By comparing Fig 5(A)–5(C), it can be seen that the relative flow of the integrated irrigation with fertilizer irrigation decreased with the increase in the irrigation frequency under muddy-water conditions. With the increase in the irrigation times, the relative flow decreased more rapidly, the clogging of the dripper occurred faster, which inevitably meant that the fertilization in muddy water would significantly accelerate the clogging of the drippers. The comparison of Fig 5(A)–5(C) shows that with a fixed sediment content of 1 g/L, when the working pressure was 40 kPa, the dripper still had not been clogged after the 9th irrigation process, while when the working pressure was 70 and 100 kPa, the dripper clogged after 7th and 9th irrigation processes, respectively. This indicated that the working pressure in muddy-water fertilization had no significant effect on the clogging of the dripper, which was consistent with the above variance analysis results. When the fertilizer concentration was 3 g/L, after the 9th irrigation process, the clogging degree of the drip irrigation tape was significantly greater than those at concentrations of 1.8 and 0.6 g/L. The degree of clogging was in the order of 3.0 g/L > 1.8 g/L > 0.6 g/L. It can be concluded that the concentration of chemical fertilizer increased the degree of clogging to a certain extent. The application and dissolution of chemical fertilizers introduce a large number of cations into the irrigation water. These cations, including Ca2+, Mg2+, Na+, and K+, neutralize the negatively charged surfaces of fine-grained sediments, compressing the double layer structure on the sediment surface. This reduction in electrostatic repulsion enhances inter-particle bonding and promotes the flocculation effect, which increases the likelihood of emitter clogging. Additionally, phosphate fertilizers can promote carbonate precipitation by reacting with calcium ions, leading to the formation of calcium phosphate. This process reduces the availability of free calcium, shifting the balance toward calcium carbonate precipitation, thereby further accelerating emitter clogging [20]. As shown in Fig 5(A)–5(C), under a working pressure of 40 kPa, the average relative flow of the three groups—1–0.6, 3–1.8, and 2–3—was 0.6, 1.8, and 3.0, respectively. The combination 1–0.6, representing lower sediment and fertilizer concentrations, experienced less flow reduction compared to groups 3–1.8 and 2–3, which had either higher sediment or fertilizer concentrations. In Fig 5(A), the flow reduction in group 1–0.6 was notably lower than in the other two groups, while the flow reduction for groups 2–3 and 3–1.8 was relatively similar. These results confirm that sediment concentration has a more pronounced impact on clogging than fertilizer concentration. Specifically, the higher the sediment concentration, the greater the flow reduction, indicating that sediment exerts a stronger influence on the average relative flow. It can be seen from Fig 5(B) that the three combinations resulted in similar variations in the average flow. Therefore, under continuous irrigation conditions, there were strong similarities in the flow and the achieved average relative flows between the three groups. It can be seen that dripper blockage was not a single physical blockage or chemical blockage in the process of muddy-water fertilization and irrigation, but a joint effect and mutual promotion occurred to caused the blockage, which was consistent with the results of previous studies [21, 22]. In conclusion, in the process of fertilization and irrigation with muddy water, the clogging of the dripper is not controlled by single physical or chemical factors, but the result of the comprehensive effect of both physical and chemical factors, which is consistent with the findings of previous studies. As shown in Fig 5, the type-H1, type-H2, and type-H3 drip irrigation tapes shared the same clogging pattern under the same conditions. This indicates that the same labyrinth channel exhibits a similar clogging pattern at different flow. 3.1. Analyse the test results under muddy-water conditions using SPSS software The range analysis and multiple comparison analysis of the main effects were carried out on the measurements under muddy-water to explore the relationship between each factor and the test index, then to determine the effects of the working pressure (B), sediment content (F), and fertilizer concentration (E). The order of importance of the influence factors on the average relative flow of the single-wing labyrinth drip irrigation tape was determined. 3.2. Test results The tests were carried out based on an orthogonal experiments scheme, and the average relative flow under muddy-water condition was calculated using formula (1). The results are shown in Table 4. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 4. UL9(33) uniform orthogonal design and test results. https://doi.org/10.1371/journal.pone.0313888.t004 3.3. Range analysis Tables 5, 6 and 7 show the range analysis results of the average relative flow for different values of the test factors in the H1, H2, and H3 single-wing labyrinth drip irrigation tapes. The order of the influence factors (laying pressure (B), sediment content (F), and fertilizer concentration (E)) on the average relative flow of the single-wing labyrinth drip irrigation tape under muddy-water conditions for the H1, H2, and H3 single-wing labyrinth drip irrigation tapes was as follows: RF > RE > RB > RD. The order of the factors affecting the average relative flow of the drip irrigation tape was as follows: F(sediment content) > E(fertilizer concentration) > B(working pressure). Download: PPT PowerPoint slide PNG larger image TIFF original image Table 5. Results of the range analysis of each factor (H1). https://doi.org/10.1371/journal.pone.0313888.t005 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 6. Results of the range analysis of each factor (H2). https://doi.org/10.1371/journal.pone.0313888.t006 Download: PPT PowerPoint slide PNG larger image TIFF original image Table 7. Results of the range analysis of each factor (H3). https://doi.org/10.1371/journal.pone.0313888.t007 The relevant factor indicators are shown in Fig 4. As shown in Fig 4(A), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1 g/L, and working pressure is 40 kPa in the type-H1 single-wing labyrinth drip irrigation tape. As for Fig 4(B), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1g/L, and working pressure is 40 kPa in the type-H2 single-wing labyrinth drip irrigation tape. As for Fig 4(C), the optimal average relative flow occurred when the fertilizer concentration is 0.6 g/L, sediment content is 1g/L, and working pressure is 70 kPa in the type-H3 single-wing labyrinth drip irrigation tape. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 4. Average relative flow of drip irrigation tape with different factor values: (a) drip irrigation tape type H1, (b) drip irrigation tape type H2, and (c) drip irrigation tape type H3. https://doi.org/10.1371/journal.pone.0313888.g004 3.4. Variance analysis and multiple comparison analysis of principal effects 3.4.1. Variance analysis. The results of the variance analysis are shown in Table 8. At the 95% probability level, the results showed that the fertilizer concentration and sediment concentration of the type-H1 drip irrigation tape reached the extremely significant level (p < 0.01). For the type-H2 and type-H3 drip irrigation tapes, the sediment concentration reached the extremely significant level, and the fertilizer concentration reached the significant level (p < 0.05). The effects of the working pressure on the relative flows of the three drip irrigation tapes did not reach the significant level. This showed that the fertilizer concentration and the sediment concentration had significant impacts on the relative flows of the drip irrigation tapes, and thus, they would be important factors causing the dripper to clog. The fertilizer concentration of the type-H1 drip irrigation tape reached the extremely significant level, while for the type-H2 and type-H3 drip irrigation tapes, it only reached the significant level. All three types of drip irrigation tapes were single-wing labyrinth flow channels, but the type-H1 drip irrigation tape was relatively narrower than the type-H2 and type-H3 drip irrigation tapes. To a certain extent, this narrow tape enhanced the collision and flocculation of sediment particles after fertilization, making it easier to form a stable agglomeration mechanism to clog the dripper. From the F values, it can be seen that the order of the factors affecting the average relative flow of the three single-wing labyrinth drip irrigation tapes was F > E > B, that is, sediment content > fertilizer concentration > working pressure, and the variance analysis results were consistent with the range analysis results. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 8. Variance analysis of average relative flow. https://doi.org/10.1371/journal.pone.0313888.t008 3.4.2. Multiple comparison analysis of principal effects. SPSS 22.0 was used to analyse the differences between different levels of the influence factors. The range analysis showed that the influence of the working pressure (B) was not significant, so multiple comparison analysis regarding to working pressure (B) was not conducted. The multiple comparison results of the principal effects are shown in Table 9. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 9. Multiple comparison analysis of principal effects. https://doi.org/10.1371/journal.pone.0313888.t009 The comparison of fertilizer concentration (E) and sediment content (F) across different drip irrigation tapes highlights several significant trends in the average relative flows. For the H1 drip irrigation tape, under different fertilizer concentration treatments, the highest average relative flow was observed in the E1 treatment (0.670), which was significantly higher than both E2 and E3 treatments. This indicates that higher fertilizer concentrations, like in the E1 treatment, may enhance the flow stability in this particular tape. Similarly, the sediment content in the H1 drip irrigation tape had a pronounced effect on the flow, with the F1 treatment showing the highest average relative flow (0.699). This suggests that lower sediment content positively impacts flow performance, as all comparisons between F1, F2, and F3 were statistically significant. In the H2 drip irrigation tape, the results were somewhat different. While the E1 treatment again produced the highest flow (0.618), the difference between the E2 and E3 treatments was not significant. This could imply that H2 tapes are less sensitive to variations in fertilizer concentration beyond a certain point. Regarding sediment content, the F1 treatment consistently showed a higher average relative flow (0.681) than the other sediment content treatments, reinforcing the idea that cleaner water conditions improve irrigation efficiency in these systems. For the H3 drip irrigation tape, the average relative flow of the F1 treatment was highest (0.698), and there was a significant 12.1% decrease in flow from F1 to F3. This pattern, observed across all treatments, suggests a strong inverse relationship between sediment content and flow performance in the H3 tape. Additionally, in terms of fertilizer concentration, the E1 treatment (0.668) had the highest relative flow, with significant differences noted across all treatments, indicating that both fertilizer concentration and sediment content substantially influence the performance of the H3 tape. 3.4.1. Variance analysis. The results of the variance analysis are shown in Table 8. At the 95% probability level, the results showed that the fertilizer concentration and sediment concentration of the type-H1 drip irrigation tape reached the extremely significant level (p < 0.01). For the type-H2 and type-H3 drip irrigation tapes, the sediment concentration reached the extremely significant level, and the fertilizer concentration reached the significant level (p < 0.05). The effects of the working pressure on the relative flows of the three drip irrigation tapes did not reach the significant level. This showed that the fertilizer concentration and the sediment concentration had significant impacts on the relative flows of the drip irrigation tapes, and thus, they would be important factors causing the dripper to clog. The fertilizer concentration of the type-H1 drip irrigation tape reached the extremely significant level, while for the type-H2 and type-H3 drip irrigation tapes, it only reached the significant level. All three types of drip irrigation tapes were single-wing labyrinth flow channels, but the type-H1 drip irrigation tape was relatively narrower than the type-H2 and type-H3 drip irrigation tapes. To a certain extent, this narrow tape enhanced the collision and flocculation of sediment particles after fertilization, making it easier to form a stable agglomeration mechanism to clog the dripper. From the F values, it can be seen that the order of the factors affecting the average relative flow of the three single-wing labyrinth drip irrigation tapes was F > E > B, that is, sediment content > fertilizer concentration > working pressure, and the variance analysis results were consistent with the range analysis results. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 8. Variance analysis of average relative flow. https://doi.org/10.1371/journal.pone.0313888.t008 3.4.2. Multiple comparison analysis of principal effects. SPSS 22.0 was used to analyse the differences between different levels of the influence factors. The range analysis showed that the influence of the working pressure (B) was not significant, so multiple comparison analysis regarding to working pressure (B) was not conducted. The multiple comparison results of the principal effects are shown in Table 9. Download: PPT PowerPoint slide PNG larger image TIFF original image Table 9. Multiple comparison analysis of principal effects. https://doi.org/10.1371/journal.pone.0313888.t009 The comparison of fertilizer concentration (E) and sediment content (F) across different drip irrigation tapes highlights several significant trends in the average relative flows. For the H1 drip irrigation tape, under different fertilizer concentration treatments, the highest average relative flow was observed in the E1 treatment (0.670), which was significantly higher than both E2 and E3 treatments. This indicates that higher fertilizer concentrations, like in the E1 treatment, may enhance the flow stability in this particular tape. Similarly, the sediment content in the H1 drip irrigation tape had a pronounced effect on the flow, with the F1 treatment showing the highest average relative flow (0.699). This suggests that lower sediment content positively impacts flow performance, as all comparisons between F1, F2, and F3 were statistically significant. In the H2 drip irrigation tape, the results were somewhat different. While the E1 treatment again produced the highest flow (0.618), the difference between the E2 and E3 treatments was not significant. This could imply that H2 tapes are less sensitive to variations in fertilizer concentration beyond a certain point. Regarding sediment content, the F1 treatment consistently showed a higher average relative flow (0.681) than the other sediment content treatments, reinforcing the idea that cleaner water conditions improve irrigation efficiency in these systems. For the H3 drip irrigation tape, the average relative flow of the F1 treatment was highest (0.698), and there was a significant 12.1% decrease in flow from F1 to F3. This pattern, observed across all treatments, suggests a strong inverse relationship between sediment content and flow performance in the H3 tape. Additionally, in terms of fertilizer concentration, the E1 treatment (0.668) had the highest relative flow, with significant differences noted across all treatments, indicating that both fertilizer concentration and sediment content substantially influence the performance of the H3 tape. 3.5. Analysis of influences of different working conditions on average relative flow It can be seen from the previous analysis that the working pressure had no significant effect on the clogging of the dripper in muddy-water condition. Therefore, only the effects of the sediment concentration and fertilizer concentration on the clogging of the dripper are discussed in this section. Fig 5(A)–5(I) show the average relative flow of the H1-type, H2-type, and H3-type drip irrigation tapes under different working pressures of 40, 70, and 100 kPa, respectively. The notation "1–0.6" represents working conditions with a sediment content of 1 g/L and a fertilizer concentration of 0.6 g/L. Download: PPT PowerPoint slide PNG larger image TIFF original image Fig 5. Changes in average relative flow under different conditions. Note: (a)–(c) show the average relative flow rate of H1-type drip irrigation tape under working pressures of 40 kPa, 70 kPa, and 100 kPa, respectively, under different sediment content and fertilizer concentration conditions. (d)–(f) show the performance of H2-type drip irrigation tape under the same pressure conditions, while (g)–(i) display the performance of H3-type drip irrigation tape. (’1–0.6’ represents a sediment content of 1 g/L and a fertilizer concentration of 0.6 g/L). https://doi.org/10.1371/journal.pone.0313888.g005 By comparing Fig 5(A)–5(C), it can be seen that the relative flow of the integrated irrigation with fertilizer irrigation decreased with the increase in the irrigation frequency under muddy-water conditions. With the increase in the irrigation times, the relative flow decreased more rapidly, the clogging of the dripper occurred faster, which inevitably meant that the fertilization in muddy water would significantly accelerate the clogging of the drippers. The comparison of Fig 5(A)–5(C) shows that with a fixed sediment content of 1 g/L, when the working pressure was 40 kPa, the dripper still had not been clogged after the 9th irrigation process, while when the working pressure was 70 and 100 kPa, the dripper clogged after 7th and 9th irrigation processes, respectively. This indicated that the working pressure in muddy-water fertilization had no significant effect on the clogging of the dripper, which was consistent with the above variance analysis results. When the fertilizer concentration was 3 g/L, after the 9th irrigation process, the clogging degree of the drip irrigation tape was significantly greater than those at concentrations of 1.8 and 0.6 g/L. The degree of clogging was in the order of 3.0 g/L > 1.8 g/L > 0.6 g/L. It can be concluded that the concentration of chemical fertilizer increased the degree of clogging to a certain extent. The application and dissolution of chemical fertilizers introduce a large number of cations into the irrigation water. These cations, including Ca2+, Mg2+, Na+, and K+, neutralize the negatively charged surfaces of fine-grained sediments, compressing the double layer structure on the sediment surface. This reduction in electrostatic repulsion enhances inter-particle bonding and promotes the flocculation effect, which increases the likelihood of emitter clogging. Additionally, phosphate fertilizers can promote carbonate precipitation by reacting with calcium ions, leading to the formation of calcium phosphate. This process reduces the availability of free calcium, shifting the balance toward calcium carbonate precipitation, thereby further accelerating emitter clogging [20]. As shown in Fig 5(A)–5(C), under a working pressure of 40 kPa, the average relative flow of the three groups—1–0.6, 3–1.8, and 2–3—was 0.6, 1.8, and 3.0, respectively. The combination 1–0.6, representing lower sediment and fertilizer concentrations, experienced less flow reduction compared to groups 3–1.8 and 2–3, which had either higher sediment or fertilizer concentrations. In Fig 5(A), the flow reduction in group 1–0.6 was notably lower than in the other two groups, while the flow reduction for groups 2–3 and 3–1.8 was relatively similar. These results confirm that sediment concentration has a more pronounced impact on clogging than fertilizer concentration. Specifically, the higher the sediment concentration, the greater the flow reduction, indicating that sediment exerts a stronger influence on the average relative flow. It can be seen from Fig 5(B) that the three combinations resulted in similar variations in the average flow. Therefore, under continuous irrigation conditions, there were strong similarities in the flow and the achieved average relative flows between the three groups. It can be seen that dripper blockage was not a single physical blockage or chemical blockage in the process of muddy-water fertilization and irrigation, but a joint effect and mutual promotion occurred to caused the blockage, which was consistent with the results of previous studies [21, 22]. In conclusion, in the process of fertilization and irrigation with muddy water, the clogging of the dripper is not controlled by single physical or chemical factors, but the result of the comprehensive effect of both physical and chemical factors, which is consistent with the findings of previous studies. As shown in Fig 5, the type-H1, type-H2, and type-H3 drip irrigation tapes shared the same clogging pattern under the same conditions. This indicates that the same labyrinth channel exhibits a similar clogging pattern at different flow. 4. Discussion At the 95% confidence level, the variance analysis results showed that the influence of the working pressure on the average relative flows of the three drip irrigation tapes did not reach significant levels. This indicated that the working pressure had no significant effect on the average relative flow of the dripper under the test conditions. However, Liu et al. studied the effect of different working pressure levels on the clogging of the dripper by using water with a high- sediment content and found that the anti-clogging ability of the dripper gradually decreased as the working pressure dropped from 100 to 40 kPa or even lower [23]. Some researchers have suggested that under high-sediment-content irrigation conditions, the sediment is more likely to settle in the pipeline, thereby reducing the flow or clogging the dripper [24, 25]. This is mainly because different influences were considered than in this study. It is necessary to consider high sediment content in subsequent studies. The results of this experiment suggest that the sediment content had a direct impact on the clogging of the dripper. In a muddy-water irrigation process, sediment filtration and other treatments before irrigation cannot completely eliminate solid particles in the irrigation water, and sediment particles entering the dripper flow channel with particle sizes less than 0.1 mm will still cause physical clogging [26]. Because the number of fine sediment particles in muddy water is relatively high, when the fine sediment particles enter the drip irrigation channel through the filter, the particles will aggregate to form larger-sized sediment particles, which will gradually accumulate and eventually clog the dripper [27]. The larger the particle size and the higher the concentration of sediment particles are in the irrigation water, the higher the sedimentation risk factor of the sediment particles is, and the more likely it is to result in the clogging of the dripper [28]. This experiment also found that under the same irrigation pressure and fertilizer concentration conditions, when the sediment content was 1 g/L, the clogging occurred after the 9th irrigation process. When the sediment content was 2 g/L, the clogging occurred after the 7th irrigation process. When the sediment content was 3 g/L, the clogging occurred after the 6th irrigation process. To prevent the clogging of the drippers, when the sediment content in the irrigation water is high, the irrigation frequency should be appropriately reduced. This is consistent with the results of Wei et al. Their study suggested that when using particles with diameters less than 0.1 mm, a certain concentration of sediment is a necessary condition for particle collision and flocculation [29]. With the increase in the sediment concentration, the distribution of the particle concentration in the flow channel of the dripper increased as well. When the sediment concentration reached a certain level (1.25 g/L), the particle concentration had a significant effect on the clogging of the dripper. The test results demonstrate that the concentration of chemical fertilizer had a direct impact on the clogging of the dripper. Within a certain range, as the fertilization concentration increased, the clogging of the dripper was more evident. This finding was consistent with the results of the study conducted by Zhou et al. [30]. This is because most fine-grained sediments are negatively charged, and cations can neutralize the compressed sediments. Application of fertilizer has been shown to alter the drip irrigation water source parameters, such as the type and concentration of nutrients, number of suspended particles, temperature, pH, and electrical conductivity. This causes mutual collision, adsorption, agglomeration, and precipitation of various solutes in the flow channel, generates turbulent flow, and leads to changes in the clogging and deposition process, thereby increasing the risk of clogging in the dripper [31]. Fertilization will also change the concentration of cations in the water, and most fine-grained sediment particles are negatively charged. The cations neutralize and compress the electric by-layer structures on the particle surfaces of the sediment [32]. After fertilization, the flocculation of sediment is enhanced, and it is easier to form a stable agglomerated structure to clog the dripper [33]. Zhou et al. pointed out that the flocculation sedimentation and structure are both affected by the ion concentration [34]. In integrated irrigation with fertilizer, the fertilizer will introduce a large quantity of cations, which will strengthen the flocculation between sediment particles [35]. Duffadar et al. pointed out that the increase in the cation concentration will enhance the bonding forces between particles, accelerate particle aggregation, and aggravate flocculation, resulting in clogging of the dripper [36]. The clogging sensitivity to sediment concentration and fertilizer concentration is different, and there is a complex coupling effect between these two factors. The concentration of chemical fertilizer affects dripper clogging by altering the physical, chemical, and biological characteristics of solutes in water, highlighting the need for further exploration of how fertilizer type and concentration influence physical, chemical, and biological clogging. Due to multiple practical factors, the types of fertilizers and drip irrigation tape samples used in this study are limited. More fertilizer types and drip tape types will be considered in future experiments. Also, it is necessary to further explore the inducement mechanism of dripper clogging in drip irrigation system by means of the content of clog, the total number of microorganisms and sediment adsorption. 5. Conclusions This study explores the combined effects of fertilizer concentration, sediment content, and working pressure on the clogging performance of single-wing labyrinth drip irrigation tapes under muddy-water conditions. The findings offer important insights into the critical factors affecting dripper performance and suggest practical strategies for improving drip irrigation system design. Firstly, the study demonstrates that sediment content and fertilizer concentration are the primary factors contributing to dripper clogging, while working pressure plays a comparatively minor role. Across all tested drip tapes (H1, H2, and H3), the highest average relative flows were observed at lower sediment content (1g/L) and fertilizer concentration (0.6g/L), underscoring the importance of managing these variables to minimize clogging risks during muddy-water irrigation. Secondly, variance analysis reveals that both sediment content and fertilizer concentration significantly impact the average relative flow, with higher levels of both factors leading to more severe clogging. This aligns with prior research, which indicates that interactions between sediment particles and fertilizer components promote chemical precipitation and particle aggregation, thereby exacerbating dripper clogging. Lastly, the results have significant implications for the design and management of integrated water-fertilizer irrigation systems. It is recommended to reduce irrigation frequency and employ sediment filtration techniques to mitigate clogging under high-sediment conditions. Future research should examine the long-term effects of various combinations of fertilizers and sediments on dripper performance to optimize the anti-clogging properties of drip irrigation systems. In conclusion, this research highlights the essential role of sediment and fertilizer management in maintaining drip irrigation efficiency and provides a foundation for future studies aimed at sustainable irrigation practices. Supporting information S1 Graphical abstract. https://doi.org/10.1371/journal.pone.0313888.s001 (JPG) Acknowledgments We would like to thank Professor Jingwei Gong for help with data analysis.
TI - Analysis of clogging factors in single-wing labyrinth drip irrigation tape
JF - PLoS ONE
DO - 10.1371/journal.pone.0313888
DA - 2024-12-31
UR - https://www.deepdyve.com/lp/public-library-of-science-plos-journal/analysis-of-clogging-factors-in-single-wing-labyrinth-drip-irrigation-0WB3FiyWTn
SP - e0313888
VL - 19
IS - 12
DP - DeepDyve
ER -