Christiansen Uniformity Coefficient Research Articles

Effects of Drip Irrigation Frequency on Emitter Clogging using Saline Water for Processing Tomato Production

AbstractAs an important parameter of drip irrigation using saline water, irrigation frequency not only affects crop growth by changing the soil moisture–salinity distribution, but also influences the anti‐clogging performance of the drip irrigation system by changing fouling growth inside emitters. Hence, a representative medium‐salt‐tolerant crop of processing tomatoes was selected as the research object. The effects of different drip irrigation frequencies (S1 (1‐day irrigation interval), S2 (2‐day irrigation interval) and S3 (4‐day irrigation interval)) on the clogging characteristics of emitters were analysed via a 2‐year drip irrigation experiment using saline water between 2013 and 2014. The results showed that the discharge ratio variation (Dra) and the Christiansen uniformity coefficient (CU) of the emitters decreased as the irrigation interval increased, while there was a negative linear correlation between Dra and the irrigation interval (R2 > 0.79). The highest Dra and CU values of 80.9 and 78.0% were observed in high‐frequency irrigation (S1) after 2 years of planting. Moreover, clogging fouling inside the emitter accumulated gradually and exhibited a significant positive linear correlation with irrigation interval time (R2 > 0.80). The chemical components of clogging fouling, which were calcium magnesium carbonates, quartz, silicates, and sodium chloride, were the same under different irrigation frequencies. The emitter clogging of drip irrigation systems using saline water for processing tomato production in the Hetao irrigation area presented a composite clogging (mainly chemical clogging associated with physical clogging). Considering previous research, a high frequency of once per day is recommended for drip irrigation using saline water. © 2019 John Wiley & Sons, Ltd.

Mechanism of intermittent fluctuated water pressure on emitter clogging substances formation in drip irrigation system utilizing high sediment water

Emitter clogging is one of the bottlenecks that restricts the application and promotion of drip irrigation technology. Applying intermittent fluctuated water pressure is regarded as an effective way to overcome drip irrigation emitter clogging when using high sediment water. Therefore, a drip irrigation experiment using Yellow River water was carried out at Deng Kou County, Inner Mongolia, China, to study emitter clogging controlling effects of three fluctuation patterns. The control group (CG) operation pressure was 40 kPa, and three intermittent fluctuated water pressure modes were 40 kPa + fluctuating water pressure for 1 h (FP1 h), 2 h (FP2 h), and 4 h (FP4 h), respectively. The system was fluctuated once every 16 h, and the amplitude of the fluctuating water pressure was 80–100 kPa with a cycle of 40 s. The characteristics of the sediment size and mineral components of clogging substances found in emitters and laterals were also analyzed. The results showed that intermittent fluctuated water pressure not only directly changed the flow velocity distribution in the emitter flow path to reduce the deposition of clogging substances, but also controlled the formation of clogging substances inside the laterals to avoid enhanced emitter clogging by transporting into the emitter. The intermittent fluctuated operating pressure could effectively reduce contents of emitter clogging substance in drip irrigation, and the longer period it was applied, the better controlling effect was observed. Comparing with the CG, applying intermittent fluctuated water pressure with constant period of 4 h would reduce the total clogging substance contents by 26%. The clay and powder particles were reduced by 56% and 34%, respectively. Meanwhile the quartz, silicate, calcium magnesium and carbonate in the clogging substances decreased by 36%, 35%, and 11%, respectively. Thus, the discharge ratio variation coefficient (Dra) and Christiansen Uniformity coefficient (CU) increased by 10.1–16.7% and 8.9–14.2%, correspondingly. These results could provide references for the application and promotion of drip irrigation technology using water with high sediment load.

Impact of irrigation water quality and envelope materials around drip line on emitter performance in subsurface drip irrigation

AbstractA field experiment was conducted to study the effect of water quality types of fresh water (FW) and treated wastewater (TWW) and envelope materials of coarse sand (CS), fine sand (FS), and control (CO) on emitter performance, dry matter yield (DMY), and water use efficiency (WUE) under subsurface drip irrigation.The main interaction effect of water quality type and envelope material on coefficient of variation, Christiansen uniformity coefficient, and emission uniformity was not significant (P < 0.05), but they have a significant effect on the average emitter discharge (Qavg), DMY, and WUE. The means of Qavg for FW with CS, FS, and CO were 7.13, 6.94, 2.65 L/h, and for TWW, they were 6.78, 6.84, and 2.35 L/h, respectively. The DMY under FW with CS, FS, and CO was 3083.87, 1367.95, and 417.45 kg/ha, and under the TWW, it was 2409.5, 1347.4, and 417 kg/ha, respectively.

HYDRAULIC PERFORMANCE OF DRIPPERS APPLYING SANITARY LANDFILL LEACHATE DILUTED IN WATER

ABSTRACT Drip irrigation with diluted sanitary landfill leachate favors the development of grasses on the landfill surface, however, the clogging of emitters of the irrigation systems is the major obstacle for this practice. The objective of this study was to select empirical models of the Christiansen's uniformity coefficient, distribution uniformity coefficient, and statistical uniformity coefficient of drip irrigation sets applying sanitary landfill leachate diluted in water as a function of time of operation, and quality of the effluent. An experiment was conducted in a completely randomized experimental design with three replicates, using a split-split plot arrangement, with operating pressures (70, 140, 210, and 280 kPa) in the plots, types of drippers (G1, 1.65 L h-1; G2, 2.0 L h-1; and G3, 4.0 L h-1) in the subplots, and operating time of the drip irrigation sets (0, 20, 40, 60, 80, 100, 120, 140, and 160 hours) in the sub-subplots. Data regarding hydraulic performance and effluent quality were acquired every 20 hours during 160 hours of operation and subjected to simple and multiple regression analyses. The G3 dripper operating at pressures of 70 and 140 kPa were the combinations that best attenuated biofilm clogging. The linear regression and square root were the models that best represented the reduction in the uniformity of the effluent application as a function of the operating time of the drip irrigation sets. The linear correlations denoted that calcium contents and total coliform population rates were the characteristics of the sanitary landfill leachate that most affected the drip clogging process.

An in-situ accelerated experimental testing method for drip irrigation emitter clogging with inferior water

Emitter clogging has become a bottleneck in the application and promotion of inferior water drip irrigation technology. Understanding the detailed emitter clogging process is the precondition and basis for solving clogging issue. However, the existing indoor simulated experiments have the disadvantages in unnecessary effect on the results, and the in-situ experimentation is difficult due to the long experiment period. Therefore, this paper proposed an in-situ accelerated (ISA) experimental testing method for studying the emitter clogging behaviors in drip irrigation systems with inferior water source. Its feasibility was verified in Dengkou in Inner Mongolia, and a comparative study was performed to examine the differences and correlations between the ISA method and the normal intermittent (NI) method for drip irrigation using Yellow River water (YRW) and brackish water (BRW). The results indicated that the drip irrigation emitter clogging behaviors via the ISA method were relatively conservative. The values of randomness of clogging occurrence (△FQt), emitter clogging degree (EC), emitter discharge variation (qvar), clogging substance on the internal laterals (CSL) and clogging substance inside emitters (CSE) were lower than those of the NI method by 24–57, 64–110, 58–121, 16–38 and 14–32%, respectively. The average discharge variation ratio (Dra), Christiansen coefficient of uniformity (CU) and statistical uniformity coefficient (Us) were 7–13, 15–23 and 17–39% higher than those of the NI, respectively. Besides, the experimental results under the two modes (ISA and NI) had significant linear correlation (0.98 > R2 > 0.75). Thus, the ISA experimental results could be converted into those under NI mode using the linear model, without considering the effects of emitter type nor the water quality. This result indicated that the ISA method could accurately reflect the clogging behaviors of the drip irrigation emitter.

Setup and calibration of the rainfall simulator of the Masse experimental station for soil erosion studies

This note describes the technical characteristics and the preliminary setup and calibration of a nozzle-type rainfall simulator installed at the University of Perugia's Masse experimental station. This simulator includes some innovative features, usually not present in similar low-cost instruments employed in field experiments: 1) both single and multi-nozzle operation are feasible, thus enabling the possibility to simulate variable-intensity rainfall events; 2) events are simultaneously reproduced in two identical plots (width 1 m, length 0.92 m, and slope 16%), thus obtaining two replications for each experiment; 3) the runoff volume coming from the micro-plots and the water volume falling outside the plots are both collected and conveyed to separate outlets, thus allowing an easy calculation of the infiltrated volumes and of the system efficiency.The first step of the calibration regarded the spatial distribution of rainfall, the stability of the rainfall intensity over time (within the experiment), and the reproducibility of the rainfall intensities both in space (between the two plots) and over time (among successive experiments). Next, the drop size distribution (DSD) and the related rainfall characteristics (median volumetric drop diameter D50 and mean kinetic energy per unit area and unit depth) were evaluated by the oil method for the single and some multi-nozzle applications. An effective automatic drop recognition procedure by the Fiji open-source software is proposed and illustrated.Results indicate a high uniformity of rainfall (Christiansen uniformity coefficient > 92%) in both single and multi-nozzle operation for both plots. The reproducibility of experiments over short time intervals and under similar environmental conditions is satisfactory (coefficient of variation of mean intensity < 3%). Comparing initial and final rainfall intensity values, a slight decrease was observed within each experiment (about 2% on average). Some systematic differences in rainfall intensity were also detected between the plots. The analysis of both the intensity and the DSD in the multi-nozzle operation indicated the presence of some interference among the individual sprays when larger nozzles are simultaneously activated. Moreover, in agreement with the literature, it was confirmed that this type of rainfall simulator always produces kinetic energy values lower than those associated with natural rainfall of similar intensity.

Comparison of two pressurized irrigation systems on lettuce seedlings production

Automatized irrigation systems under nursery conditions have become an essential tool to satisfy rationally the water needs for plants without forgetting the sustainability aspects. The present study aimed to evaluate two sprinkler irrigation systems under nursery conditions: one with fixed laterals (fixed system) and another with self-propelled laterals (mobile system) and study the effect of their use on the behavior of tree lettuce seedlings production. The experiment was conducted on a greenhouse with a polystyrene (PVC) plastic film coverture and laterals closed with 60% plastic screen. The statistical design used was a 2x3 completely randomized factorial with four replicates, and the results analyzed using the Tukey test. To compare the lettuce seedlings behavior under both irrigation systems it was evaluated the leaves number, seedling's height, root length and fresh and dry mass of the aerial and root part of the plant. The Christiansen uniformity coefficient (CUC) and the water distribution coefficient (WDC) for the fixed irrigation system were considered adequate and for the self-propelled laterals system (mobile system) they were considered excellent. The volume of water used with the fixed system was 109.12% higher than with the self-propelled system. The lettuce seedlings irrigated with the self-propelled system had a growth, production and a seedling quality statistically superior than when irrigated with the fixed system. Independent of the irrigation system used, the Elizabeth lettuce cultivar had a greater seedling behavior. According with the results obtained, it is recommended the use of the self-propelled irrigation system (mobile system) on the production of lettuce seedlings.

Low-pressure sprinkler irrigation in maize: Differences in water distribution above and below the crop canopy

Reducing the working pressure at the sprinkler nozzles is one of the alternatives to reduce energy requirements in solid-set sprinkler irrigation systems. Previous studies reported ≈10% lower seasonal Christiansen uniformity coefficient (CUC) for low-pressure treatments than for standard treatments, but no differences in maize yield. This research analyses the effect of maize canopy water partitioning on irrigation performance indexes (CUC and wind drift and evaporation losses, WDEL). Three irrigation treatments were considered, based on the working pressure: 1) A standard brass impact sprinkler operating at a pressure of 300 kPa (CIS300); 2) A standard brass impact sprinkler operating at a pressure of 200 kPa (CIS200); and 3) A modified plastic impact sprinkler (with a deflecting plate attached to the drive arm) operating at a pressure of 200 kPa (DPIS200). Irrigation performance was measured using a catch-can network located above the maize canopy (CUCac, WDELac) along the whole crop season and using stemflow and throughfall devices below the maize canopy (CUCbc, WDELbc) in eight irrigation events. Maize growth, yield and its components were measured. Under low-wind and fully developed canopy conditions (a frequent situation for maize irrigation), CUCbc resulted higher than CUCac for the low-pressure treatments, while the opposite was observed for the standard pressure treatment. Maize canopy partitioning reduces the differences in irrigation performance indexes between pressure treatments, explaining why there are no differences in grain yield between them. Caution should be used when measuring sprinkler irrigation performance above tall canopies, since the elevation of the catch-cans and the crop canopy partitioning affect performance estimations.

Effects of Drip Irrigation Models on Chemical Clogging under Saline Water Use in Hetao District, China

Saline water is a major resource for agricultural irrigation in arid-semi arid regions, especially when it is combined with drip irrigation. However, highly saline water can easily cause clogging of the emitters in drip irrigation systems, adversely affecting crop growth. Hence, a 2a processing tomatoes drip irrigation study was conducted in Hetao irrigation district. The chemical clogging of the emitters was analyzed using four drip irrigation models: RI1 (all fresh water irrigation), RI2 (saline water use in the flowering stage, fresh water in the fruiting stage), RI3 (fresh water use in the flowering stage, saline water in the fruiting stage), and RI4 (all saline water irrigation). The results revealed that the discharge ratio variation (Dra) and the Christiansen uniformity coefficient (CU) of RI4 decreased to 74.0% and 70.9%, respectively, which is considered as a clogged condition with poor irrigation uniformity. When compared to the all saline water irrigation model, the Dra and CU of fresh-saline alternating irrigation models (RI2 and RI3) were higher by 12.16% and 18.05%, respectively. Additionally, the dry weight (DW) of emitters fouling was less than that of RI4 by 16.30%. The Dra and CU showed linear relationships (R2 &gt; 0.79) for the different irrigation models. However, as the Dra declined, the more adverse influence on maintaining the high CU was found in RI4. Using irrigation models with alternating fresh-saline water were recommended to control chemical clogging in drip irrigation systems. Calcium carbonate (CaCO3) was the dominant scale formed, which caused the emitters to clog when processing tomatoes were grown using a drip irrigation system with saline water.

Effects of lateral spacing for drip irrigation and mulching on the distributions of soil water and nitrate, maize yield, and water use efficiency

In this study, a two-year study in fields with and without a subsurface sand layer (identified as FSS and FNS) were conducted in the Hetao Irrigation District in Northwest China, to investigate the effects of irrigation lateral spacing and soil mulching on soil water and nitrate distribution uniformity, and the combined effects of soil water and nitrate distribution on crop yield and water use efficiency (WUE) of spring maize. The experiment followed a completely randomized block design with four treatments (S1M1, S1M2, S2M1, and S2M2) and three replicates for FSS and FNS, respectively. The four treatments resulted from the combination of two levels of lateral spacing (S1 for 1.0 m and S2 for 0.5 m) and two film-covering modes (full mulching, M1; partial mulching, M2). In each treatment, the Christiansen uniformity coefficient (CU) was used to evaluate the uniformities of soil water (CUw) and nitrate (CUn) distribution in the vertical soil profile. The results showed that the narrower lateral spacing and full mulching enhanced CUn and relative chlorophyll content of leaf, compared with the wider lateral spacing and partial mulching. However, lateral spacing and mulching methods imposed no significant effect on CUw. The correlation between CUw and CUn was not significant under mulched drip irrigation system. In soils without a subsurface sand layer, crop yield may be greater with a higher CUn in root zone. Full film-covering significantly enhanced CUn and then increased crop yields and WUE in FNS, however the combined effects of lateral spacing and mulching methods on grain yield were not significantly different. Thus, taking into account crop yields, WUE, and cost of drip laterals, the combination of wider irrigation lateral spacing and partial mulching was recommended for the FSS soil, while the combination of wider irrigation lateral spacing and full mulching for the FNS soil.

Performance of drip emitters for different pressures and application of cashew nuts wastewater

Este estudio tuvo como objetivo analizar el efecto de diferentes presiones de operación en la obstrucción de goteros y en el coeficiente de uniformidad de Christiansen (CUC) en los sistemas de riego por goteo que operan con la agua residual de castanha de cajú. El experimento se estableció en el esquema de parcelas subsubdivididas, con presiones de operación en parcelas (70, 140, 210 y 280 kPa), tipo de goteros en parcelas subdivididas (G1, G2 y G3) y los tiempo de operación em parcelas subsubdivididas (0, 20, 40, 60, 80, 100, 120, 140 y 160 h), en el diseño completamente al azar con tres repeticiones. El CUC de unidades de riego se midió cada 20 h hasta que el tiempo de funcionamiento de 160 h. Los resultados mostraron que los goteros G2 y G3 son los más adecuados para la aplicación de la agua residual de castanha de cajú, y la presión de funcionamiento de 140 kPa minimiza la obstrucción en los goteros G1, G2 y G3 cuando se opera con la agua residual de castanha de cajú.

Development and calibration of a rainfall simulator for hydrological studies

ABSTRACT Rainfall Simulators (RS) have been used as tools for researches involving the estimation of runoff and infiltration on permeable pavements as well as in evaluating storm build-up and wash-off processes on pavements and roofs. Data obtained with the use of RS allows building a database with parameters which are useful in the implementation of BMPs taking local environment conditions into consideration. The purpose of this study was to develop and calibrate a handy and low-cost RS for hydrological researches. The developed RS can reproduce rainfall with intensities from 40 mm h-1 to 182 mm h-1. The RS is able to simulate rainfall events with drops of median diameter (D50) of 2.12 mm and kinetic energy of 22.53 J mm-1m-2, which represent 90.12% of the kinetic energy produced by a natural rainfall. Spatial distribution of simulated rainfall, which is expressed by the Christiansen's Uniformity Coefficient, was considered satisfactory with a value of up to 87.80%. The developed RS can be used as an alternative for the acquisition of hydrological data in a reduced period of time, under standardized experimental conditions and independently of natural rainfall events. The RS is also capable to simulate rainfall events with varying intensity.

Effects of micro-sprinkling hose length and width on wheat field water condition and flag leaf chlorophyll fluorescence characteristics in different sampling districts

A two-year field experiment was conducted in 2014-2015 and 2015-2016 wheat growing seasons to study the effects of micro-sprinkling hose length and width on field water condition, and flag leaf chlorophyll fluorescence characteristics in different sampling districts (D1 to D6 along with the hose laying direction). Six micro-sprinkling hose treatments were set: 60 m (T1), 80 m (T2) and 100 m (T3) lengths under 65 mm width; 60 m (T4), 80 m (T5) and 100 m (T6) lengths under 80 mm width. The results showed that after irrigation at jointing, the Christiansen uniformity coefficient (Cu) of T1 was significantly higher than T2 and T3 under 65 mm hose width. Under 80 mm hose width, T4 and T5 had the highest Cu compared to T6. After irrigation at anthesis, the Cu showed T1>T2>T3 under 65 mm hose width, and T4>T5>T6 under 80 mm hose width. Under 65 mm hose width, the average relative soil water content of 0-40 cm soil layers after irrigation at anthesis, flag leaf ΦPSII, NPQ and ETR at 20 and 30 d after anthesis and the grain yield of different sampling district did not differ in T1; T2 showed the order of D1, D2>D3>D4>D5; T3 showed D1, D2>D3>D4>D5, D6. The average ΦPSII, NPQ and ETR at 20 and 30 d after anthesis, and the average dry matter at maturity of different sampling districts were presented as T1>T2, T3. Under 85 mm hose width, no significant differences were observed in the average relative soil water content of 0-40 cm soil layers after irrigation at ahthesis, flag leaf ΦPSII, NPQ and ETR at 20 and 30 d after anthesis and the grain yield of different sampling districts in T4; in T5, the indexes mentioned above in D1, D2 and D3 sampling districts were significantly higher than those in D4 and D5; in T6, the decreasing order was D1, D2, D3>D4>D5>T6. The average ΦPSII, NPQ and ETR at 20 and 30 d after anthesis, and the average dry matter at maturity of different districts showed the order of T4, T5>T6. The ave-rage grain yield and water use efficiency of T1, T4 and T5 were significantly higher than those in T2, T3 and T6, T1 and T4 had a better irrigation benefit than T5. Under this experimental condition, T1 treatment under 65 mm hose width, T4 treatment under 80 mm hose width were the most recommendable treatments considering high yield and water saving, and T5 treatment was also recommendable under 80 mm hose width.

Research on the Fine-Scale Spatial Uniformity of Natural Rainfall and Rainfall from a Rainfall Simulator with a Rotary Platform (RSRP)

Abstract: The accurate production of a rainfall environment similar to natural rainfall by a rainfall simulator (RS) is a crucial and challenging task in rainfall instrument testing or calibration. Although the spatial uniformity of rainfall accumulation is a key parameter of an RS, the spatial uniformity comparison between simulated rainfall and natural rainfall, and the spatial uniformity improvements for an RS are scant in the literature. In this study, a fine-scale natural rainfall experiment was studied using the same testing methods of an RS and the rainfall uniformity was evaluated using the Christiansen Uniformity Coefficient (CU). Simultaneously, factors influencing the spatial uniformity of natural rainfall, including the average rainfall accumulation (RA), the deviation of RA, and the area of the test zone, were analyzed. The results successfully reproduced some of the behaviors observed in natural rainfall experiments, showing that CU is dependent on these parameters. Based on these studies, we developed a rainfall simulator with a rotary platform (RSRP) and found that although spatial uniformity of the RSRP was greatly improved using an appropriate rotary speed, it was not consistent with the spatial uniformity of natural rainfall. Furthermore, we tested four tipping-bucket rain gauges using this imperfect RSRP, and found that the RSRP might acquire the instrumental errors associated with RA for a tested rainfall instrument.

Performance Evaluation of Constant Versus Variable Rate Irrigation

AbstractVariable rate irrigation (VRI) can increase water use efficiency and productivity by applying water based on site‐specific needs. In this study, the performance of a five‐span centre‐pivot irrigation system (CPIS) retrofitted with a commercial variable‐rate irrigation package was evaluated at constant and variable application depths at the Alberta Irrigation Technology Centre (AITC) in southern Alberta, Canada. Two sets of experiments were designed to investigate the uniformity of application of the system during the 2013 and 2014 growing seasons. The first set of catch‐can trials were carried out with three irrigation rates in the direction of pivot travel. Three different wind regimes were observed during the catch‐can trials. Catch‐cans were arranged in grid configurations within the experimental plots located under one irrigation zone in span 4. The Christiansen coefficient of uniformity (CU) ranged from 90.4 to 94.4%. Wind speeds of 3.3 and 6.5 m s‐1 negatively and significantly impacted the CU values. The second set of catch‐can trials were performed with used and new sprinklers in a transect along the pivot lateral during the 2014 growing season. The Heermann and Hein coefficient of uniformity (CUHH) ranged from 89.0 to 93.5% and from 81.7 to 94.4% with constant and variable application depths, respectively. The greatest (94.4%) and least (81.7%) CUHH values were observed where water applications were 100 and 40% of the set point, respectively. Overall, the uniformity of application of CPIS retrofitted with the commercial VRI package both along the system's lateral and in the travel direction were above 90% for the majority of the trials under the different wind speeds and water application depths. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Drip irrigation lateral spacing and mulching affects the wetting pattern, shoot-root regulation, and yield of maize in a sand-layered soil

Soil with a 20–60cm thick subsoil (60–90cm below the surface) sand layer has been recently reclaimed to exploit its grain production potential in an arid region in northwest China. A 2-year field study was conducted in the Hetao irrigation district to investigate the effects of lateral spacing and soil mulching methods under drip irrigation on the soil moisture, NO3−, shoot-root regulation, and water use efficiency (WUE) of spring maize. The Christiansen uniformity coefficient (Cus) was adopted to evaluate soil moisture and NO3− distribution, which was calculated with soil water content and NO3− concentration. The four studied treatments consisted of two irrigation lateral-spacings (A1: 1.0m, A2: 0.5m) and two film-covering modes (M1: fully mulched, M2: partially mulched) were arranged.Soil moisture was most affected by mulch coverage (full or half surface coverage) under low frequency irrigation lateral spacing (adjacent to or between crop rows) under high frequency irrigation. Lateral spacing exerted a notable influence on soil moisture at a 20cm depth, while the mulching method influenced soil moisture mainly at 40cm. Irrigation frequency and close lateral spacing can effectively enhance Cus. Based on our observations, a decrease in the Cus of soil NO3− may occur under frequent fertigation, particularly when irrigation laterals are between crop rows. The mulching method can play an important role in improving the concentration and Cus of soil NO3−, while the A2 treatments can slow the decrease of the Cus of soil NO3− under frequent fertigation. Root length density (RLD) under A1 treatments were lower close to lateral while higher away from lateral than A2 treatments. Close lateral spacing can result in high hundred gain weight (HGW) and high harvest index (HI) while exerting a more conspicuous effect than the mulching method by extending the grain filling stage.Frequent fertigation (i.e. once every three days) after jointing is preferentially recommended in a sand-layered field. A1M2 should be chosen for higher HI and low cost. If frequent fertigation is infeasible, A2M1 can be a good choice under low frequency fertigation.

Effect of pulsating pressure on labyrinth emitter clogging

Emitter clogging has a direct impact on the performance and service life of a drip irrigation system. A study of labyrinth emitter clogging was conducted to determine the effects of pulsating versus constant pressure on average emitter flow rate ( $$\overline{q}$$ ), the Christiansen uniformity coefficient (Cu), and the location of clogged emitters. Under constant pressure, emitters in this study began to be clogged after the 8th irrigation, whereby 15 emitters eventually became clogged; the average emitter flow rate decreased to 75% of the original emitter flow rate ( $${{q}_{0}}$$ ) after the 15th irrigation, and Cu decreased rapidly by 68.2%. For pulsating pressure, emitters began to be clogged after the 14th irrigation, only 5 emitters became clogged, and $$\overline{q}$$ only decreased to 85.3% of $${{q}_{0}}$$ , and Cu declined by only 22.6%. These results demonstrate that the anti-clogging performance of emitters with pulsating pressure is better than with constant pressure. Emitter clogging at a constant pressure generally occurred at the inlet and front of labyrinth channels, mainly due to deposition of sediment particles. Emitter clogging with pulsating pressure is due to other impurities (e.g., debris of Teflon tape) besides sediment particles plugging the labyrinth channel. Pulsating pressure is recommended for use in drip irrigation to prevent emitter clogging.

Controlling mechanism of chlorination on emitter bio-clogging for drip irrigation using reclaimed water

Drip irrigation using reclaimed water or polluted surface water involves a higher risk of bio-clogging, which is the most typical and the most complex type of clogging, and the clogging of drip irrigation emitters limits the use and spread of drip irrigation technology. Due to its strong oxidizing effect, chlorination has been considered as the most effective method of controlling emitter bio-clogging. However, the detailed controlling mechanism has remained unclear until now. Meanwhile, there have been no unified standards established for chlorination to refer to. Therefore, field experiments were carried out in a sewage treatment plant, where the reclaimed water after secondary treatment was treated with the Cyclic Activated Sludge System (CASS) process that had been incorporated to the drip irrigation system to study the controlling mechanism and impacts on non-pressure-compensating emitter bio-clogging. There were three chlorination treatments studied, which included 2.5mg/L×2h (low concentration, long duration), 5.0mg/L×1h (moderate concentration and duration), and 10mg/L×0.5h (high concentration, short duration). The results showed that the chemical chlorination could control the microbial growth in the bio-clogging substances effectively, with the microbial phospholipid fatty acids (PLFAs) decreased by 8.3%–36.1%, the number of microbial species decreased by 2–3, the microbial activity decreased by 2.6%–23.2%, and the secretion of extracellular polymeric substances (EPS) decreased by 19.8%–43.4%. Thus, the bio-clogging substances were well controlled, and the contents of solid particles (SD) content decreased by 4.8%–48.2% compared to the non- chlorinated treatment, while the discharge ratio variation (Dra) and Christiansen uniformity coefficient (CU) increased by 14.7%–22.8% and 6.77%–19.9%, respectively. However, the effects of different chlorination modes varied significantly. Chlorination with a low concentration and a long contacting duration decreased microbial activity, and better controlled emitter bio-clogging. Thus, the chlorination treatment of 2.5mg/L×2h was recommended in the drip irrigation system using reclaimed water treated with CASS technology.

Enhancing the spatial rainfall uniformity of pressurized nozzle simulators

PurposeRainfall simulators are used on experimental hydrology, in areas such as, e.g., urban drainage and soil erosion, with important timesaving when compared to real scale hydrological monitoring. The purpose of this paper is to contribute to increase the quality of rainfall simulation, namely, for its use with scaled physical models.Design/methodology/approachTwo pressurized rainfall simulators are considered. M1 uses three HH-W 1/4 FullJet nozzles under an operating pressure of 166.76 kPa and was tested over a 4.00 m length by 2.00 m width V-shaped surface. M2 was prepared to produce artificial rainfall over an area of 10.00 m length by 10.00 m width. The spatial distribution of rainfall produced from a single nozzle was characterized in order to theoretically find the best positioning for nozzles to cover the full 100 m2 area with the best possible rainfall uniformity.FindingsExperiments with M1 led to an average rainfall intensity of 76.77-82.25 mm h−1 with a 24.88 per cent variation coefficient and a Christiansen Uniformity Coefficient (CUC) of 78.86 per cent. The best result with M2 was an average rainfall intensity of 75.12-76.83 mm h−1 with a 21.23 per cent variation coefficient and a CUC of 83.05 per cent.Practical implicationsThis study contributes to increase the quality of artificial rainfall produced by pressurized rainfall simulators.Originality/valueM2 is the largest rainfall simulator known by the authors worldwide. Its use on rainfall-runoff studies (e.g. urban areas, erosion, pollutant transport) will allow for a better understanding of complex surface hydrology processes.

Uniformity microsprinkler irrigation system using statistical quality control

ABSTRACT: The objective of this study was to evaluate the use of statistical quality control tools in the analysis of the uniformity of a microsprinkler irrigation system. For the analysis of irrigation Christiansen uniformity coefficient (CUC) and the distribution uniformity coefficient (DU) were statistically analyzed by means of the Shewhart control charts and process capability index (Cp). For the experiment 25 tests were carried out with a single micro sprinkler and subsequently seven different spacing between micro sprinklers were simulated. Control charts contributed to the diagnosis of the treatments to be under control and with satisfactory uniformity outcomes. Increase in process capability index was directly proportional to the average of CUC and DU.