Emitter Flow Rate Research Articles

Backpressure effects on the flow-pressure relation of driplines

ABSTRACT For drip irrigation design and management, it is necessary to know the relation between flow and pressure acting on emitters. In the case of subsurface drip irrigation, the backpressure phenomenon may change the hydraulic characteristics of emitters. Thus, this study aimed at determining such relationship between flow and pressure of different driplines in surface and subsurface conditions; aiming to find possible differences in hydraulic behavior. We tested four emitter types; two pressure compensating (D5000 and Hydro PCND) and two non-pressure compensating (TalDrip and Jardiline). Emitter flow rates were attained in atmospheric conditions and submerged in water, in which submergence levels represented backpressure. Assays were performed using inlet pressures of 80, 100, 120, and 150 kPa for the Hydro PCND dripline and 25, 50, 100, and 150 kPa for the other ones; the backpressures were of 0.49, 1.47, 2.45, 4.41 and 6.37 kPa with four replications. The emitters had their proportionality constants and discharge exponents changed in submerged applications, representing backpressure effect. Non-pressure compensating emitters had their discharge exponent decreased, while in pressure compensating ones, it was increased. Backpressure reduced emitter flow rates at all evaluated pressures.

Evaluation of Drip Irrigation Emitters Distributing Primary and Secondary Wastewater Effluents

Drip irrigation is a reliable and efficient way to deliver water to the soil; however, drip emitter clogging is a major concern when irrigating treated wastewater. Four types of drip irrigation emitters from three manufacturers were analyzed over a one-year period to monitor the incidence of clogging and its effect on irrigation uniformity. A controlled laboratory experiment was conducted using two different types of pressure compensating emitters designed for reclaimed wastewater, one type of non-pressure compensating emitter designed for reclaimed wastewater, and one type of non-pressure compensating agricultural emitter designed for potable water applications. Emitters of each type distributed tap water, primary treated septic tank effluent, and secondary treated sand filter effluent. Emitter flow rates were measured each month to identify clogged or flow restricted emitters. Some clogging was seen in each type of emitter over the course of the experiment and emitter flow rates fluctuated over time, suggesting that clogging was gradual and often incomplete. Many of the emitters exhibited a cyclical flow rate indicating that clogging was reversible. The emitters distributing septic tank effluent exhibited the most significant reduction in flow. The most severely clogged emitter experienced a reduction of 63% after one year of irrigation with septic tank effluent. Secondary treatment using the sand filter showed the least clogging in all four types of emitters. One of the reclaimed wastewater emitter types experienced an average reduction in flow of 1% while the other two actually increased in flow by1% and 4% after one year of irrigation with effluent from a sand filter. Water quality appeared to have a more pronounced effect than did emitter type. The effect of wastewater type on emitter discharge was +3.3% for tap water, -9.4% for septic tank effluent and -0.3% for effluent from secondary sand filtration. While the agricultural drip emitters experienced a significant negative impact after one year of operation the three drip emitters designed for distributing septic tank effluent and reclaimed wastewater showed little clogging and a high degree of uniformity.

Control of Sweetpotato Whitefly with Insecticides Applied to Soil and Foliage of TYLCV Tolerant and Susceptible Staked Tomatoes, 2015

Bemisia tabaci is the most damaging tomato pest in Florida due primarily to its role as a vector of tomato yellow leaf curl virus (TYLCV), although moderate populations can cause irregular ripening syndrome. This trial evaluated the effectiveness of different insecticide rotations and application methods to control SWF and reduce yield losses caused by both pest and virus in TYLCV-tolerant and -susceptible cultivars. Two sets of three raised beds 420 ft long were prepared at the Southwest Florida Research and Education Center in Immokalee, FL, on 6-inch centers incorporating ∼50% of the necessary fertilizer (10-2-10 NPK). Two drip tapes with 8-inch emitter spacing and flow rate of 0.67 gpm/100 ft were laid on each bed which was then covered with black polyethylene film. Chemigation was then used to fumigate beds with 300 lb/acre PicClor 60 EC 10 on 19 Feb. Seedlings of a TYLCV-tolerant variety ‘Ridge Runner’ and a susceptible variety ‘Rocky Top’ obtained from a commercial greenhouse were transplanted 18 inches apart on 6 Mar 2014, and the rest of the fertilizer requirement was injected through the drip over the course of the …

Soil and Foliar Applications of Systemic Insecticides for Control of Sweetpotato Whitefly on Zucchini Squash, 2015: Table 1

Sweetpotato whitefly, also known as silverleaf whitefly is a serious of pest of curcubit vegetables in southwest Florida. Feeding can result in loss of yield and fruit quality due to silverleaf disorder but watermelon growers can experience catastrophic losses from watermelon vine decline caused by squash vein yellowing virus transmitted by B. tabaci . We prepared three raised beds 32 inches wide on 6-ft centers and 430 ft long for this trial on 22 Jan at the Southwest Florida Research and Education Center in Immokalee FL. Two drip tapes with 8-inch emitter spacing and flow rate of 0.67 gpm/100 ft were laid on each bed which was then covered with whiteface polyethylene film and fumigated with 300 lbs/acre Pic-Clor 60 EC (chloropicrin 56.7% + 1-3 dichloropropene 37.1%) injected through …

Liquid Corn and Fish Fertilizers Are Good Options for Fertigation in Blackberry Cultivars Grown in an Organic Production System

The impact of organic fertilizer source on the growth, fruit quality, and yield of blackberry (Rubus L. subgenus Rubus Watson) cultivars (Marion and Black Diamond) grown in a machine-harvested, organic production system for the processed market was evaluated from 2011 to 2013. The planting was established in Spring 2010 using approved practices for organic production and was certified in 2012. Plants were irrigated using a dripline under a woven polyethylene groundcover (weed mat) installed for weed management. Two sources of liquid fertilizer were evaluated: 1) a corn steep liquor and fish waste digestion blend (“corn”; 2.5N–1.1P–1.2K); and 2) a fish solubles and molasses blend (“fish”; 4N–0P–1.7K). Fertilizers were applied by fertigation through the drip system at rates of 56 kg·ha−1 nitrogen (N) per year in 2011–12 and 90 kg·ha−1 N in 2013. The impact of fertigation on drip system performance was evaluated with two maintenance options, “flushing” and “no flushing” of the driplines. Total yield differed among years, whereas fruit soluble solids concentration and firmness as well as floricane biomass at pruning showed a year × cultivar interaction. ‘Black Diamond’ had greater total yield and average fruit weight than ‘Marion’, but produced a greater proportion unmarketable fruit. There was no effect of fertilizer source on yield, fruit quality, primocane length, or primocanes/plant in any year with the exception of fruit weight, which was greater with corn than with fish. ‘Marion’ had a greater floricane biomass when fertilized with fish than with corn. Soil nutrients were within the recommended range, except for boron (B), which was below recommended levels. Only soil nitrate-N was affected by fertilizer source, which was greater in ‘Marion’ than in ‘Black Diamond’ when fertilized with fish. Primocane leaf tissue nutrient concentrations were within recommended levels for all nutrients, except for calcium (Ca) and B, which were below recommended standards in both cultivars. Primocane leaf potassium (K) and zinc (Zn) concentrations were greater with fish than with corn. There was no fertilizer source or maintenance effect on emitter flow rate of the drip system in either year. However, flow rates decreased an average of 4.5% in the first year and 19% in the second year. Overall, there were no differences between the fertilizers on plant growth, yield, or fruit quality, and both fertilizers were suitable for planting establishment.

A mobile application to calculate optimum drip irrigation laterals

The parameters to be taken into account when installing a drip irrigation system include the diameters of piping to be used in the irrigation installation. Certain applications developed for PC permit an approximate calculation of these diameters outside the installation environment, which makes on-site optimization of the system difficult. This paper presents a software application developed for Android mobile devices by which the user can immediately evaluate the responsiveness of all of the available optimum commercial diameters to operational changes, such as changing water demands (e.g., cultivation, water needs, and spacing), types of emitters used in the installation, or lateral feeding (from an extreme or from an intermediate point). The input data mainly required by the application are: emitter flow rates, the number of emitters, the space between emitters, the average pressure in the lateral, and the pressure tolerance. As a result, the application indicates if each irrigation lateral is valid or not for the situation provided by the user, and displays some graphics of the pressures in the lateral that indicate the pressures at the system's extremities, which permits identification of the critical points of the irrigation lateral.

Analytical Approach Determining the Optimal Length of Paired Drip Laterals in Uniformly Sloped Fields

Microirrigation plants, if properly designed, allow for water use efficiency to be optimized and high values of emission uniformity to be obtained in the field. Disposing paired laterals, for which two distribution pipes extend in opposite directions from a common manifold, can contribute to reducing the initial investment cost that represents a limiting factor for small-scale farmers of developing countries where in the last decade, the diffusion of such irrigation systems has been increasing. The objective of this paper is to propose an analytical approach to evaluate the maximum lengths of paired drip laterals for any uniform ground slope, respecting the criteria to maintain emitter flow rates or the corresponding pressure heads within fixed ranges in order to achieve a relatively high field emission uniformity coefficient. The method is developed by considering the motion equations along uphill and downhill sides of the lateral and the hypothesis to neglect the variations of emitters’ flow rate along the lateral as well as the local losses due to emitters’ insertions. If for the uphill pipe, the minimum and the maximum pressure heads occur at the upstream end and at the manifold connection, respectively, on the downhill side, the minimum pressure head is located in a certain section of the lateral, depending on the geometric and hydraulic characteristics of the lateral, as well as on the slope of the field; a second relative maximum pressure head could also exist at the downstream end of the pipe. The proposed methodology allows in particular the number of emitters in uphill and downhill sides of the lateral to be determined separately, and therefore, once fixing emitter’s spacing, the length of the uphill and downhill laterals and the position of the manifold. Applications and validation of the proposed approach, considering different design parameters, are finally presented and discussed.

Impact of water temperature and structural parameters on the hydraulic labyrinth-channel emitter performance

The effects of water temperature and structural parameters of a labyrinth emitter on drip irrigation hydraulic performance were investigated. The inside structural parameters of the trapezoidal labyrinth emitter include path width (W) and length (L), trapezoidal unit numbers (N), height (H), and spacing (S). Laboratory experiments were conducted using five different types of labyrinth-channel emitters (three non-pressure compensating and two pressure-compensating emitters) commonly used for subsurface drip irrigation systems. The water temperature effect on the hydraulic characteristics at various operating pressures was recorded and a comparison was made to identify the most effective structural parameter on emitter performance. The pressure compensating emitter flow exponent (x) average was 0.014, while non-pressure compensating emitter’s values average was 0.456, indicating that the sensitivity of non-pressure compensating emitters to pressure variation is an obvious characteristic (p<0.001) of this type of emitters. The effects of water temperature on emitter flow rate were insignificant (p>0.05) at various operating pressures, where the flow rate index values for emitters were around one. The effects of water temperature on manufacturer’s coefficient of variation (CV) values for all emitters were insignificant (p>0.05). The CV values of the non-pressure compensating emitters were lower than those of pressure compensating emitters. This is typical for most compensating models because they are manufactured with more elements than non-compensating emitters are. The results of regression analysis indicate that N and H are the essential factors (p<0.001) to affect the hydraulic performance.

Performance of different filter combinations with surface and subsurface drip irrigation systems for utilizing municipal wastewater

Large volumes of wastewater (WW) are being generated worldwide as a consequence of rapid urbanization and growth of industries. The reuse of WW finds increased application in irrigation but the presence of toxic elements and microorganisms limits its use for irrigation purpose. To reduce the contamination of WW for irrigation, drip system is seen as an appropriate choice due to restricted quantity of water application. Emitter clogging is viewed as the main problem associated with drip system for its large-scale use with WW. Physical and chemical characteristics of WW were determined and compared with groundwater (GW). Higher EC, pH, Mg, and CO3 were observed in the GW but higher turbidity, total solids, HCO3, and Ca were observed in the WW. The population of total coliforms (2.72 × 104 to 5.2 × 107) and E. coli (1.8 × 103 to 2.64 × 106) were detected in WW. The hydraulic performance of drip emitters was studied for 2 years with WW and GW using sand media filter (F1), disk filter (F2), and combination of both filters (F3). Higher removal efficiency for turbidity, total solids, Ca, Mg, CO3 total coliforms, and E. coli was observed with combination filter. Emitter discharge exponent was also close to 0.5 with combination filter. Emitter flow rate decreased (in the sequence of F1 > F2 > F3) with increase in time of operation. After 2 years of operation under F3, coefficient of variation was less than 4 % with both WW and GW. Thus, it showed good performance in surface placed emitters but it was 7.2 % with WW and 9.5 % with GW under subsurface (15 cm) placed emitters. Clogging of emitters was controlled by flushing. Flushed emitters placed at 30 cm depth resulted in 3.7 % reduction in discharge as compared to 8.7 % reduction in the absence of flushing, under filter F1. Emitters with F2 produced least improvement in discharge.

Irrigation Systems Evaluation for Living Walls

AbstractLiving walls are becoming popular solutions to alleviate negative effects of urban development. They are vertical greening systems that allow vegetation to spread across a wall surface to cover a building facade or an interior wall. Because of their characteristics, irrigation becomes essential, but the infrastructure and management required differ from a regular irrigation system. This study aims to evaluate the influence of variables such as the type of substrate used, emitter flow rates, and drip line and emitter spacing on the system performance in terms of water losses and irrigation uniformity. The results show that the main differences are marked by the type of substrate used and the emitter flow rate. Higher flows are recommended when using recirculation systems, as more uniformity is achieved in spite of the higher runoff losses. In “run-to-waste” systems, the use of lower flows and short irrigation lengths (increasing the frequency) is advised. Some management recommendations such as irr...

Assessment of clogging effects on lateral hydraulics: proposing a monitoring and detection protocol

Ageing of drip irrigation systems due to clogging of emitters is considered the largest maintenance problem in microirrigation and this problem is enhanced in subsurface irrigation systems. Whatever the source of the clogging problem, a methodology for early detection of clogging in the field can be useful in decision-making about deploying cleaning processes (flushing or injection of chemicals) and avoiding replacement of laterals. This work presents a methodology for simulating clogging conditions able to reproduce the effects of clogging on pressure profiles, head loss, and emitters flow rate distribution along a single levelled lateral with constant inlet pressure. This methodology was validated by several experiments conducted under controlled conditions of clogging induced by changes in the flow rate of emitters. The effects of clogging intensity and position on hydraulic parameters of a single lateral were analysed in detail and aspects relating to pressure, head loss, and flow rate measurements were discussed. For a given lateral set-up, it is possible to draw a chart relating flow rate and head loss for various levels and positions of clogging. Assuming that measurements of head loss and flow rate are available, this diagram enables immediate estimation of the level and location of clogging, which is useful for deploying maintenance routines. Finally, a protocol was proposed to detect the level of clogging and estimate its position along a levelled lateral under constant inlet pressure. Although constant lateral inlet pressure is atypical in large agricultural settings, it may occur in greenhouse or experimental settings.

Soil-wetting front in surface and subsurface drip irrigation

Surface and subsurface drip irrigation systems have been applied to increase irrigation efficiency and uniformity, mainly in arid and semi-arid regions. Determining soil-wetting dimensions around a point source emitter is essential for better design of drip irrigation systems. Laboratory experiments were thus conducted to measure the soil-wetting front for various arrangements of surface and subsurface drip irrigation in terms of emitter number, installation depth and flow rate. The two-dimensional numerical model Hydrus-2D was used to simulate water movement around the emitter(s) in silty loam soil. The shapes of observed and simulated soil-wetting front were almost ellipsoid and spherical for surface and subsurface drip irrigation respectively. The 2D model proved better at estimating the dimensions of the soil-wetting front when using one emitter than when using two emitters for irrigation. Both simulations and observations indicated that wetting velocity was greater during irrigation than during soil moisture redistribution. The model under- and overpredicted wetting area during irrigation and redistribution respectively, but there were no significant differences between measured and predicted values of wetting area for surface and subsurface drip irrigation. The model generally proved effective in simulating soil water flow for various kinds of surface and subsurface drip irrigation systems in silty loam soils.

Application of Computational Fluid Dynamics to Design High Performance Drip Irrigation Emitters

xH k Q ⋅ = , where Q is the flow rate (l/hr), k is an emitter constant, H is the pressure head (kPa), and x is the emitter flow rate exponent. The constants k and x are always used to evaluate emitter’s hydraulic performance. Therefore, the structure can be optimized according to the evaluation parameters till reaching a satisfied result. On the other hand, emitter clogging has been considered one of the most annoying problems inhibiting the popularization of drip irrigation; it can be caused by physical, chemical or biological contaminants [4-5]. Regardless of which kind of the clogging, it can be ascribed to the deposition of particles with different diameters (sand, indissolvable carbonate, bacteria etc.) in emitters. Usually, we conclude the drip irrigation whether is clogged or not based on the flow rate at the same pressure head. We are not sure why and how emitter’s discharge is reduced? CFD can simulate the motion and trajectories of particles and visualize the single particle’s stagnation position by using stochastic trajectory model. In addition, by means of Eulerian-Eulerian model, potential deposition regions of plenty of solid particles can be obtained, which can be used to explain the clogging mechanism of emitters [6]. These simulation results are good criterions for structural optimization of emitters. CFD is an effective technique to discover the flow behavior of the fluid in labyrinth channels which is important for the microcharacteristics of the emitter. The researchers and manufacturers can design serials of high-performance emitters by using CFD.

Design of Nonzero Uniformly Sloping Laterals in Trickle Irrigation Systems

An analytical method was developed to design evenly sloping, pressurized, nontapered, multiple-outlet pipes. Assuming spatiotemporal continuity of emitter flow rates, the approach was derived from the solution of analytical nonlinear differential equations. A straightforward relationship was established between the inlet discharge, the lateral slope, the diameter, and the pressure head at the upstream and downstream ends. Five pressure head grade line profiles were derived: uniformly uphill, level ground, steeply downhill, moderately downhill, and slightly downhill. For moderately downhill laterals, the theoretical analysis revealed that the pressure head at the outermost rim was independent of the inlet discharge. For the other profiles, the pressure head at the downstream edge was parameterized as a function of the inlet discharge. The iterative computation of the inlet discharge is a prerequisite for the inference of the other design parameters. This approach was successfully compared with the stepwise method that is deemed to be the most accurate.

Hydraulic design procedure for drip irrigation submain unit based on relative flow difference

The combined effects of hydraulic variation and manufacturing variation on the relative flow difference in drip emitters were analyzed for a drip irrigation submain unit. Emitter manufacturing variation is a random variable and follows a normal distribution, which can be expressed by emitter coefficient of manufacturing variation (v) and a random variable (u) following a standardized normal distribution. Emitter flow rate equation can be expressed by two parts: (1) emitter discharge coefficient (k) and discharge exponent (x) determine the flow rate (khx) from an emitter at pressure head (h) and (2) the unknown random term (uvkhx), taking into account emitter manufacturing variation. Next, the formula for relative flow difference in a drip irrigation submain unit is derived based on (1) hydraulic variations due to head loss and elevation differences and (2) emitter manufacturing variation. A new hydraulic design procedure for drip irrigation submain unit is proposed based on the formula.

Estimativa de dimensões de volume de solo molhado na irrigação por gotejamento superficial em solo de textura média: condição inicial de solo seco

The use of models to describe or estimate the water distribution in the wetted soil volume can be an important alternative in the definition of the irrigation management and design. The objective of this work was to estimate dimension data of soil wetted volume generated in different soil types under surface drip irrigation using mathematical models of the literature. There were selected data from one class of soil (loam soil), simulating three emitter flow rates (0.503, 1.48 and 2.70 L h-1) and 12 soil water application times (1 to 12 h) with a dry initial soil condition. The values of the wetting pattern were estimated (maximum width and maximum depth) by the five studied models (one numerical, one analytical and three empirical). The simulated maximum width ranged from 18.67 to 108.89 cm and maximum depth ranged from 5.98 to 61.75 cm. The numerical (PSIGS) and analytical (WetUp) models present more reliable results. The empirical model DIPAC presents results with values and behavior similar to those of more robust models.

Bacterial application increased the flow rate of CaCO3-clogged emitters of drip irrigation system

CaCO(3) is one of the most common emitter clogging factors among chemical precipitates in drip irrigation systems. Continuous acid application as a classical approach to prevent CaCO(3) clogging can be tricky, expensive and hazardous for soil. In order to develop an environmentally friendly method to address the problem, two bacterial strains, one renowned as a PGPR and the other having extensive CaCO(3) dissolving capacity, were used in treatments of artificially clogged drip irrigation emitters. Results showed the flow rates of clogged emitters significantly increased in drip lines which were treated with bacterial suspensions but no increase was observed in control drip lines which were treated with sterile nutrient broth. Furthermore, scanning electron and florescence microscopies were used to examine residual CaCO(3) precipitates. Thus, in consideration of its extensively studied PGPR characteristics, microbial treatment with Bacillus subtilis OSU-142 was shown to be promising for field applications as a novel and environmentally friendly treatment for clogged emitters of drip irrigation systems.

Hydraulic Performance of Drip Irrigation System with Municipal Wastewater

Generation of wastewater in huge amounts is putting a lot of pressure on irrigation engineers for its safe disposal or reuse in agriculture. Though wastewater could contribute to major and minor nutritional requirement of crops, but the presence of microbial contaminants and toxic elements limits its use. Utilization of wastewater for irrigation through drip irrigation system seems to be a good choice to reduce the chances of contamination due to restricted quantity of water application. Since clogging in such a situation would be the main problem, its remediation is required for enhanced utilization of wastewater through drip irrigation system. Physical and chemical characteristics of wastewater were determined and compared with ground water. While higher EC, pH, Mg, and carbonate were observed in ground water, wastewater contained higher turbidity, total solids, HCO3 , and Ca. Population of total coliforms (2.72x104 to 5.2x107) and E. coli. (1.8x103 to 2.64x106) were detected in wastewater. The hydraulic performance of drip emitters was studied for two years (2009 and 2010) with municipal wastewater and ground water using gravel media (F1), disk filter (F2) and combination of gravel and disk filters (F3). Filtration using F3 gave emitter discharge exponent close to 0.5 with R2 value of 0.99. Emitter flow rate decreased with increase in time of operation of the system. Coefficient of variation less than 4% with wastewater and ground water showed excellent performance in surface placed drip lateral after two years of operation. After filtration with F3, coefficient of variation (CVq) of 4.0 % with wastewater and 6.46 % with ground water was observed under subsurface (15 cm deep) placement of laterals.

Wetting Pattern Models for Drip Irrigation: New Empirical Model

Reliable information about the wetted dimensions of soil under drip irrigation helps designers to determine optimal emitter flow rates and spacings to reduce system equipment costs and provide better soil water conditions for the most efficient and effective use of water. This study presents a new empirical formula that predicts soil wetted dimensions around a drip emitter. The coefficients were obtained by using regression analysis on the results of field experiments done on the Pardis Agricultural Farm of Tehran University in Karaj, Iran. These data were also used to evaluate the semiempirical model of Zur and Schwartzman, the empirical model of Amin and Ekhmaj, and the analytical model WetUp. Statistical comparisons (mean error, root mean square error, and model efficiency) are made of the simulated data with the observed data. To evaluate the models, published experimental data by Risse et al. and Li et al. were also used. The results demonstrate that the suggested equations can be used for a wide ran...

REVISING WETTED SOIL VOLUME UNDER TRICKLE SOURCE FOR IRRIGATION SCHEDULING

Wetted soil shape under trickle irrigation is an important parameter in irrigation scheduling and design in agricultural farms. Irrigation water should not be beyond crop root zone to avoid deep percolation. Moreover, irrigation water applied should adequate crop water use in irrigation interval. The purpose of this work is to figure out the suitable shape of wetted soil based on soil type, flow rate, and crop water use. A field experiment was conducted in sand, silt and clay soils under trickle source with varying flow rates as 2, 4, 8, 16, and 24 liter/h. Squash, corn, and grape crops were selected to represent different root zones for irrigation scheduling. Field results showed that horizontal and vertical water movements were related to both emitter flow rate and soil intake rates. Suitable flow rate and irrigation interval were found for selected soil and crop types. Soil moisture content was contoured directly after irrigation and soil-water redistribution. Optimal flow rates were 2 and 4 liter/h in clay soil, 8 and 16 liter/h in loam, 16 and 24 liter/h in sand. Adjusted method was recommended to calculate irrigation interval by revising wetted root zone volume, taking into account different soil, crops, crop stages, and seasons.