Irrigation System Uniformity Research Articles

Failure behavior of pressure compensating emitter under different operation pressures in drip irrigation systems

Pressure compensating emitters (PCE) can maintain a consistent irrigation flow rate under varying pressures through its internal compensation diaphragm and effectively improve the irrigation uniformity of drip irrigation systems. However, the PCE function is prone to failure, particularly when using marginal water, which can cause various technical and economic problems. To date, little is known about the failure behavior of PCE. This study investigated the effects of three pressures (0.1Mpa, 0.2Mpa, and 0.3Mpa) on the failure behavior of PCE. Then the dynamic changes in clogging substances and diaphragm performances in PCE channel were monitored. The results showed that as the system operation increased, the performance of PCE gradually decreased. The CU>80% running time was 172.8–634.9 h, and the flow index >0.2 running time was 120.1–768.1 h. The failure of PCE is primarily caused by two factors: clogging of the PCE flow channel and deterioration of the diaphragm mechanical performances. The flow rate of PCE increased by 22.6% on average at 0.3Mpa compared to 0.1Mpa, and clogging substances in the PCE flow channel decreased by 19.8%. Meanwhile, increasing the operating pressure improved the mechanical performance of the diaphragm. Under the operating pressure of 0.3Mpa, the diaphragm’s elasticity and hardness increased by 14.6% and 12.8%, respectively. Therefore, this study is of significance in popularizing PCE drip irrigation technology and marginal water utilization.

Multi-factorial failure of pressure-compensating emitters in drip fertigation systems: An in-situ sampling investigation

Pressure-compensating emitter (PCE) is an important equipment to improve irrigation and fertigation uniformity of drip irrigation system. Due to multiple factors, PCE failure would lead to the whole drip irrigation system failure and consequently affect the crop growth. However, few studies reported the key reason and influential factors of PCE failure yet. Therefore, an in-situ sampling study of PCE, which was collected from 16 different operating locations and all were operated for several years in the apple orchard, was conducted in this paper. The effects of water quality characteristics and climatic conditions on the fouling formation inside PCE and the mechanical properties of the elastic diaphragm were analyzed. The result indicated that the PCE relative average discharge (Dra) decreased by 4.65%− 33.19% after 3–9 years. The phosphorus content, average temperature, suspended particles, and pH showed significant impacts on fouling accumulation inside the PCE flow channel, particularly biofouling. Meanwhile, the stretch rate, elastic modulus, tensile strength, and the hardness of PCE elastic diaphragm were mainly affected by humidity conditions, longitude, SO42- content and pH. Both the fouling accumulation and elastic diaphragm variations synthetically decreased the Dra of the drip irrigation system. This study provides theoretical support to further improve the irrigation uniformity of drip irrigation systems.

A Comparative Study of Standard Center Pivot and Growers-Based Modified Center Pivot for Evaluating Uniformity Coefficient and Water Distribution

The center pivot irrigation system is a type of irrigation technology used to apply water effectively and uniformly over a wide variety of areas and topographies. These irrigation systems’ uniformity of water application greatly affects water use, energy consumption, and crop production. Performance tests of the standard lateral galvanized and modified polyethylene plastic pipes in the center pivot irrigation systems were conducted in different regions of Saudi Arabia. Water distribution depths along the laterals, coefficient of uniformity (CU), and distribution uniformity of the low quarter (DU) were determined. The results revealed that profiles of water distribution ranged from 4 to 14 mm for the standard-center pivot irrigation systems, while those for the modified-center pivot irrigation systems ranged from 6.5 to 50 mm. Standard-center pivot irrigation systems’ CU values ranged from 74 to 90%, with an average of 86%. In comparison, the modified-center pivot irrigation systems’ CU values ranged from 62 to 83%, with an average of 78%. The DU values ranged from 60 to 82% for the standard-center pivot irrigation systems, with an overall average of 77%. For the modified-center pivot irrigation systems, the DU values, in contrast, ranged from 31 to 75%, with an average of 65%. Thus, the accuracy and uniformity of the standard-center pivot irrigation systems are superior to those that have been modified. Additionally, a statistical model was developed to investigate the relationship between the water losses and the main climatic factors under field operating conditions. Therefore, the study results are expected to draw attention to standard lateral pipes’ value on the one hand and demonstrate the detrimental consequences of growers’ incorrect practices in pivot irrigation systems, motivating them to take strong action against these activities, on the other hand.

Simulation analysis of the effects of friction on the performance of pressure regulator for drip tape

Pressure regulators (PRs) are critical equipment to ensure the safety and uniformity of irrigation systems, and their performance and stability are affected by the friction produced by the seal rings. This paper addresses the effects of friction on the performance of a drip tape inlet PR sealed by an O-ring. A dynamic numerical model considering the friction force was developed. The performance of the PR and characteristics of motion of the internal moving parts under different friction levels, inlet pressures, and flow conditions were calculated and analyzed. The results show that the simulated precision for outlet pressure is improved by considering the friction and depends on the magnitude of the friction force and working stages of the PR. Compared with a corresponding model where the friction is neglected, for friction levels of 2.5 N and 5 N, the normalized root mean square error (nRMSE) of the outlet pressure decreases by 3.8% and 6.9% in the transition stage and by 0.8% and 4% in the regulating stage, respectively. According to the response characteristics of the displacement curve of the regulating cup with respect to the variation in the regulation performance curve, the performance curve can be divided into three stages: the pressure raising stage, the transition stage and the regulating stage. Friction causes obvious outlet pressure fluctuations in the latter two stages by affecting the displacement increments of the moving parts, especially in the transition stage. Greater friction corresponds to greater fluctuations (expressed in terms of the variation coefficient of outlet pressure, CV) in the regulation performance curve, and the fluctuation amplitude increases with increasing flow rate. A PR with greater friction has a smaller applicable flow rate range to remain below a certain CV limit. When the friction is less than 7.5 N, the PR is suitable for a flow range of 400–1000 L/h. The rate of variation in the outlet pressure (δPout) increases as the friction increment and flow rate increase and the inlet pressure decreases. δPout can be greater than 20%, mainly in the transition stage and when the friction increment is greater than 7.5 N. Considering the changes in outlet pressure caused by the lubricant loss and O-ring aging during long-term use of PRs, regular inspection and maintenance are recommended for PRs installed downstream of a submain, especially ones with long drip tapes.

Comparing the Relationship of Different Drip Irrigation Uniformity Parameters with Crop Yield

Drip irrigation system has the ability to apply water over the field uniformly. Uniformity of drip irrigation can be measured through many parameters. Uniformity is one of the procedures which should be considered in drip irrigation design and management to gain the maximum possible crop yield. The objective of this study was to investigate the effect of some uniformity parameters including Christiansen’s uniformity coefficient (UC), distribution uniformity (DU), Manufacturing coefficient of variation (CVf), and emission uniformity (EU) on crop yield and water productivity, in addition to evaluate the strength of the relationship between each of studied uniformity parameter and crop yield. Four operating pressure heads 5, 10, 15, and 20m were used to operate the irrigation system to make the required change in drip irrigation system uniformity level. The study included two crops which were lettuce and turnip. Results indicated that increasing drip irrigation system uniformity will lead to increase crop yield and water productivity of both crops. Values of correlation coefficient (r) were less than 0.5 for all uniformity parameters when correlated to crop yield. This indicated that uniformity might not be the most important factor representing the quantity of crop yield though its importance. According to the values of the (r) resulted from the relationship between each uniformity parameter and crop yield; EU had the strongest effect on crop yield. The study recommended modeling the relationship between drip irrigation uniformity and crop yield basing on EU.

Applying high-resolution visible-channel aerial imaging of crop canopy to precision irrigation management

Canopy cover (or vegetation cover) maps serve in irrigation management mainly to determine the primary evapotranspiration (ET) coefficient, as radiation interception and evaporative surface area are directly related to canopy cover. Crop size and development with time depends on water supply; therefore, crop canopy maps are tools for the detection of the spatial uniformity of irrigation systems. Several aerial scan campaigns were deployed in the Upper Galilee of Israel in the 2017 and 2018 growing seasons to follow up and evaluate the irrigation uniformity and crop coefficients of peanuts and cotton by RGB scans of a Phantom 4 multirotor unmanned aerial vehicle (UAV) and DJI Mavic-Pro UAV equipped with RGB and near-infrared (NIR) sensors. Foliage intensity and coverage were enhanced by a green-red vegetation index (GRVI), which is a normalized difference vegetation index (NDVI)-like process where the green channel replaced the NIR. The results demonstrated that the GRVI is suitable for the purpose of determining the vegetation cover. Furthermore, the GRVI yielded better results than the NDVI in recognizing phenological crop changes (especially senescence) and in detecting heterogeneity in field irrigation. Therefore, this research proves the applicability of a low-cost digital camera mounted on an easily accessible UAV for crop cover and actual, in-field, ET coefficients determination and irrigation uniformity evaluation.

Using the step by step models to evaluate field application uniformity of subsurface drip irrigation systems

Compared to other irrigation methods, drip irrigation systems (DI) are considered one of the most efficient form of irrigation. Subsurface drip irrigation allowed reducing water losses by evaporation, runoff, and deep percolation comparing to other irrigation systems supplying water on soil surface. Field evaluation of Uniformity of water applications and its stability, however, are still a matter of controversy and deserve more investigation, since the collection of water discharged needs to excavate the soil around the emitters. Experiments carried out at the Department of Rural and Agrifood Engineering of Polytechnic University of Valencia allowed describing a methodology to assess the performance of drip irrigation through hydraulic characterizations and an emission uniformity coefficient, using the step by step models. Calculations evidenced that operating pressures on emitters ranged between 127.6 kPa and 131.7 kPa, whereas the corresponding flow rates varied from 4.00 L/h and 4.07 L/h, with an average value of 4.02 L/h. Variability in the emitters’ flow rate resulted very limited due to the short length of the lateral (25.6 m). However, more attention should be paid to this for a longer field dimensions. Consequently, the value of emission uniformity coefficient was equal to 96.3%, testifying the uniform water distribution within the sub-plot.

Impacts of center pivot irrigation system uniformity on growth of potato crop and residual soil nitrogen

Maintaining the homogeneity of soil nitrogen (N) and plant vigor across agricultural fields is a major concern for farmers and agricultural scheme planners, particularly fields that are irrigated through pressurized systems, such as center pivots. Therefore, this study was carried out on a 30 hm2 potato field located 650 km south of Riyadh, the capital city of the Kingdom of Saudi Arabia, to investigate the impacts of the center pivot irrigation distribution uniformity on the crop development and the spatial distribution of residual soil N. Irrigation performance test was designed to investigate water application rate and distribution uniformities. The overall water application uniformity coefficients (Cu), determined through Christiansen (Cud) and Heerman (CuH) methods, were determined at 81.29% and 80.64%, respectively. However, the overall water distribution uniformity (Du) was determined at 70%. A considerable variability in the distribution uniformity of irrigation water was observed across the experimental field (a Du value of 67% over the medium spans compared to a Du value of 88% over the inner spans). Results of this study showed a linear correlation between the irrigation water distribution uniformity and the soil N (R2=0.88). On the other hand, the vegetation cover distribution, indicated by the Cumulative Normalized Difference Vegetation Index (CNDVI), was not found to be much responsive to the irrigation distribution uniformity (R2=0.11). A time series of successive NDVI maps extracted throughout the potato crop growth stages showed a consistent trend in the distribution of NDVI across the field, with R2 values that ranged between 0.25-0.73. Keywords: irrigation performance, uniformity, center pivot, potato, soil nitrogen, NDVI DOI: 10.25165/j.ijabe.20191201.3684 Citation: Al-Gaadi K A, Hassaballa A A, Tola E, Kayad A G, Madugundu R, Assiri F, et al. Impacts of center pivot irrigation system uniformity on growth of potato crop and residual soil nitrogen. Int J Agric & Biol Eng, 2019; 12(1): 126–131.

Effect of manifold layout and fertilizer solution concentration on fertilization and flushing times and uniformity of drip irrigation systems

Applying fertilizer through drip irrigation system is a very important method to save fertilizer and labour. Three manifold layouts (water supply in one end for transversal drip tapes (M1), water supply in both ends for transversal drip tapes (M2) and water supply in one end for longitudinal drip tapes (M3)) and four different fertilizer solution concentrations (50.00 g L−1 (C1), 66.67 g L−1 (C2), 100 g L−1 (C3) and 200 g L−1 (C4)) were selected to investigated the effect of the manifold and concentration on water fertigation uniformity. Results showed that the emitter at the extreme end of the manifold needed more time to clean the rudimental fertilizer in the drip tapes. The minimal flushing time increased from 8 to 13, 4 to 7 and 7 to 12 min with increasing the fertilizer concentration from C1 to C4 for M1, M2 and M3, respectively. The drip irrigation system needed more time for flushing to reduce the risk of emitter clogging when a higher fertilizer solution concentration was applied. In order of performance, M2 had the highest water and fertilizer uniformity, followed by M3 and lastly by M1. The fertilizer solution concentration had no significant effect on water distribution. However, it had a significant effect on fertilizer distribution. The mass of the applied fertilizer for the drip tapes close to the inlet increased with increasing fertilizer solution concentration from C1 to C4, which indicated that higher fertilizer solution concentration can result in lower fertilizer distribution uniformity. There was a significant effect of the manifold layout on water uniformity. The fertilizer concentration and the interaction between manifold layout and concentration had no significant effect on the water uniformity. Similarly, both the manifold layout and concentration had a significant effect on fertilizer uniformity. The interaction between manifold layout and concentration had a significant effect on the Christiansen’s uniformity (CU) and distribution uniformity (DU) for fertilizer, whilst, a significant effect on emission uniformity (EU) was not found. The manifold layout and fertilizer solution concentration should therefore be considered in the design and operation of fertigation system.

Comparison of Water Distribution Characteristics for Two Kinds of Sprinklers Used for Center Pivot Irrigation Systems

Sprinkler selection influences the water distribution uniformity of center pivot irrigation systems. The sprinkling uniformity of the center pivot is crucial for the yield and quality of crops on a large scale. Rotating and fixed spray plate sprinklers (RSPSs and FSPSs) are the two most popular types. However, sprinkler selection is mainly based on price, not on differences in performance between them. Under low-wind field conditions, the water distributions of individual RSPSs and FSPSs with different nozzles (2.78, 4.76, and 6.75 mm in diameter) were measured using a catch can method. Cubic spline interpolation was used for data conversion for FSPS measurements; the nozzle configuration model was used to simulate the water distribution of the same-nozzle-sprinkler pipe section and full circular irrigated areas in a simulated center pivot under three sprinkler intervals of 1.5, 3.0, and 4.5 m respectively. Results showed that (1) individual RSPSs distributed the most water around the sprinkler, whereas individual FSPSs distributed the most water over a ring-shaped region at the periphery of the sprinkler, and the wetted radii for RSPSs and FSPSs ranged from 4.88 to 7.05 m and from 5.02 to 6.85 m, respectively; (2) same-nozzle-sprinkler pipe sections of RSPSs distributed the most water around the central axes of the pipe sections, and their sprinkling uniformities were 44.7%–51.0%, whereas FSPSs distributed the most water over both sides of the axes symmetrically, and less water around the axes, with sprinkling uniformities of 40.3%–58.0%; and (3) the sprinkling uniformities of the full circular irrigated areas were 85.8%–91.7% and 85.8%–86.2% when using RSPSs and FSPSs, respectively, under different sprinkler intervals, and the uniformities were 3.1% and 6.2% higher using RSPSs than FSPSs with sprinkler intervals of 3.0 and 4.5 m, respectively. RSPS accommodated larger sprinkler intervals (>3.0 m) and maintained superior sprinkling performance when compared with FSPS.

Evaluation of Drip Irrigation System Uniformity on Cotton Yield in an Arid Region using a Two‐Dimensional Soil Water Transport and Crop Growth Coupling Model

AbstractAppropriate drip irrigation system uniformity can maintain a higher crop yield and reduce the initial investment of the system. In this study, investigating the optimal drip system uniformity for cotton, a two‐dimensional soil water transport and crop growth coupling model was calibrated and validated by soil water dynamics, crop growth indices and cotton yield obtained from mulched drip irrigation field experiments in an arid region of Xinjiang Uygur Autonomous Region, China. The model performed well with the normalized root mean square error of 2.6–22.6% for soil moisture, 6.3–14.1% for leaf area index, 4.9–7.2% for above‐ground biomass, and with the difference ranging from 2.5 to 8.2% for seed cotton yield (SCY). Next, SCYs were simulated under five Christiansen uniformity coefficients (CUs) of 55, 65, 75, 85 and 95% with three irrigation levels of 50, 75 and 100% full irrigation treatment. The predicted SCY was found to decrease as CU decreased under different irrigation treatments, and the more obvious effect of CU on SCY at 75 and 100% full irrigation treatment was obtained. In addition, SCY increased by 2.8–8.0% when CU increased from 55 to 75%, and increased by 0.1–4.6% when CU increased from 75 to 95%. Therefore, a target drip irrigation uniformity of CU = 75% was recommended to obtain a higher cotton yield, while maintaining a lower installation cost in the arid region. Copyright © 2017 John Wiley & Sons, Ltd.

ANÁLISE COMPARATIVA DE METODOLOGIA DE COLETA DE DADOS PARA AVALIAÇÃO DE SISTEMAS DE IRRIGAÇÃO LOCALIZADA

In certain situations, the evaluation of 32 or more emitters for irrigation sector can be very laborious, it being possible for the measurement at only 16 points is sufficient to determine the uniformity of the water system. The research objective with this work propose a methodology to be used in the field to determine the uniformity of irrigation small localized irrigation systems. The estimated irrigation system was installed on a particular production lot, grown with the culture of guava, located in Acarau Low Irrigation District belonging to the National Department of Works Against Drought. For the assessment of uniformity of water distribution were used four different methods: standard methodology (Christiansen, 1942), which is the collection of data on all issuers of the area to be assessed; methodology proposed by Deniculi et al. (1980), which consists of data collection 32 issuers; methodology proposed by Keller & Karmeli (1975) which is the collection of 16 issuers and methodology proposed by this study, which is a collection of 9 issuers data. The results of this field work showed that the evaluated system showed low efficiency, according to the values of the coefficients of uniformity and application efficiency, which performed far below the recommended by the specialized literature on the subject. The use of the methodology proposed in this study proved to be acceptable for evaluation of trickle irrigation systems similar to those used in this study, ie small.

Assessing the Effects of Drip Irrigation System Uniformity and Spatial Variability in Soil on Nitrate Leaching through Simulation

Abstract. Both drip system uniformity and spatial variability in soil are important factors affecting deep percolation and nitrate leaching. The effects of the two factors on deep percolation and nitrate leaching at a typical irrigation quota for maize were assessed using the water and solute transport model HYDRUS-2D. The evaluation of the influence of soil variability on nitrate leaching using a global sensitivity analysis approach demonstrated that the spatial variabilities of saturated hydraulic conductivity, saturated water content, and initial water and nitrate contents in soil imposed significant effects on nitrate leaching. Deep percolation and nitrate leaching were then simulated under five Christiansen uniformity coefficients (CU) of 50%, 60%, 70%, 80%, and 95% under different variabilities of the four soil properties mentioned above. The results indicated that nitrate leaching decreased slightly with increase in CU, while it increased considerably with spatial variability of soil properties. For a typical irrigation event of maize, the nitrate nitrogen (NO 3 -N) leaching rate decreased from 2.0 to 1.1 kg ha -1 and from 6.2 to 5.5 kg ha -1 as CU increased from 60% to 95% for an assumed homogeneous field and a field having medium variability, respectively. A considerable increase of NO 3 -N leaching rate was observed as the system uniformity decreased from 60% to 50%, although the effect of system uniformity on nitrate leaching was damped by the spatial variability in the soil. Drip irrigation system uniformities as low as 60%, which are lower than the current standards, might be used without negatively affecting nitrate leaching.

Sprinkler irrigation uniformity: Impact on the crop yield and water use efficiency

In this work, an assessment of the effect of distribution uniformity over water use efficiency is shown. The experimental study took place in Sebha region, southern Libya, characterized by arid climate and interested a barley field. The results of water irrigation in the sprinkler irrigation system with respect to the operating pressure (P) and raiser height of sprinkler (H) are reported with respect to distribution uniformity and water use efficiency. The main objective of irrigation is to apply the optimum amount of water to the crop root zone that is needed for its growth and maturation, and it is, hence, important for to check the uniformity of irrigation systems in order to adjust the operating parameters involved. To assess uniformity, the coefficient of uniformity (CU), the low quarter distribution uniformity (DU), and the coefficient of variation (CV) were considered, while the grain yield (GY), the crop height (CH) and the water use efficiency (WUE) weremeasured in order to find the best solution in terms of operating conditions. The highest values reached by the uniformity parameters with varying the operating conditions defined the best operating practices under which the irrigation system works efficiently: the results demonstrated that the maximum values for CU and DU, 91.37% and 0.85, respectively, were obtained at the highest P and H, and under the same conditions, also grain yield, plants height and WUE recorded the highest values: 5.50 t·ha−1, 63.49 cm and 0.75 kg·m−3, respectively. The results emerged in this work can be useful for similar arid regions like Sebha region, in order to solve the problems related to water scarcity and water use efficiency.

Analysis of Water Distribution Uniformity for Two Types of Sprinklers used in Sprinkler Irrigation Systems under Various Climatic and Hydraulic Conditions

In order to increase the distribution uniformity of sprinkler irrigation systems, some influential parameters such as wind speed, arrangement, space and type of sprinklers must be studied and controlled. In this study, a set of experiments were conducted based on ISO 7749/2(1990) standard to evaluate the ADF 25 0 and Nelson, F80APV sprinklers. To study the effects of wind velocity, operating pressure, various sprinkler layouts and spacing on water distribution uniformity, the experiments were conducted based on a single sprinkler method. Four operating pressures in the range of one recommended by the manufacturer for each sprinkler were applied and three sprinklers’ spaces on lateral pipelines (22, 26, and 30 m) were simulated for square and rectangular layouts to estimate the water distribution uniformity. Results showed that the distribution uniformity of Nelson sprinkler in existing wind velocities and operating pressures had smaller changes than ADF sprinkler. The 4.5 bar pressure for ADF sprinkler was better than other pressures, and operating pressures for Nelson sprinkler did not have any significant effect on distribution uniformity. With the decrease of sprinkler spacing to the wetting diameter in the simulated space, uniformity coefficient was increased. The recommended sprinkler spacing to the wetting diameter for these sprinklers ranged from 0.4 to 0.5 for square and rectangular layouts.

CIRRIG: Weather-based Irrigation Management Program for Container Nurseries

A goal of irrigation best management practices in container nurseries is to conserve water while maintaining optimal plant growth and quality. A web-based, container irrigation management program (CIRRIG) was developed to automatically provide daily irrigation run times for sprinkler-irrigated crops in container nurseries. The program estimates evapotranspiration rates based on weather uploaded from a weather station located on-site and plant production conditions monitored in each zone and adjusts irrigation run times based on irrigation application rate, the plant’s irrigation-capturing ability (for sprinkler irrigation), desired leaching fraction, and irrigation system uniformity. For this project we interfaced CIRRIG output with a programmable logic controller (PLC) to automatically irrigate a sprinkler-irrigated crop at a container nursery in Florida. Sweet viburnum (Viburnum odoratissimum) in 10-inch-diameter containers were grown by the nursery for 24 weeks in adjacent irrigation zones, one controlled automatically using CIRRIG and the other by the nursery’s traditional practice of manually turning on and off irrigation. Water use was monitored with flowmeters and plant growth by measuring plant size and shoot dry weight periodically throughout the trial. Plant growth was not different (P < 0.05) because of irrigation practice. CIRRIG reduced water use during the study period by 21% (42 vs. 53 inches) compared with the nursery’s irrigation practice. An assessment of the water-saving benefits of making daily adjustments to irrigation run times based on weather including rain indicated savings of 25% and 40% compared with biweekly adjustments with and without automatic rain cutoff, respectively. This trial demonstrated that CIRRIG coupled with an on-site weather station and a computer-controlled irrigation system can be used to manage irrigation while conserving water in a container nursery.

Effects of drip irrigation system uniformity and nitrogen applied on deep percolation and nitrate leaching during growing seasons of spring maize in semi-humid region

Drip system uniformity is one of the important factors affecting the deep percolation and nitrate leaching under drip-irrigated crops. Field experiments were conducted during two growing seasons of spring maize (Zea may L.) in 2011 and 2012 in North China Plain to evaluate the influence of drip irrigation system uniformity on deep percolation and nitrate leaching under semi-humid conditions. In the experiments, three Christiansen uniformity coefficients of 59, 80, and 97 % (the equivalent distribution uniformity DU values were 57, 71, and 95 %, respectively) and three levels of nitrogen applied at 0, 120, and 210 kg ha−1 were tested. The results of the study demonstrated that nitrate leaching was most importantly affected by the nitrogen applied, followed by the initial nitrogen content in the soil and the drip irrigation system uniformity. An increasing amount of nitrogen applied and initial nitrogen content increased the seasonal nitrate leaching significantly, while an improving system uniformity decreased the nitrate leaching. The conventional nitrogen application rate of 210 kg ha−1 could be reduced, and an extremely low drip uniformity of less than 60 % is not recommended to reduce the risk of deep percolation and nitrate leaching in the semi-humid region of North China Plain.

Metodologia simplificada para a estimativa em campo da uniformidade de sistemas de irrigação por gotejamento superficial

In irrigated agriculture, the evaluation of the parameters affecting the quality of irrigation is of fundamental importance, especially those related to water distribution uniformity. The aim with this work proposes a methodology for the estimation of flow distribution uniformity of surface drip irrigation systems under field conditions. The evaluation procedure consists of a simplified graphical technique which uses approximately half of the collected data, in an evaluation of a surface drip irrigation system, and can also be used for a quick field evaluation. In this procedure, the time to fill a container is used in place of the emitter discharge rate to determine the Uniformity. Using this technique, the listed for filling the container installed in their predetermined positions in the subunit, Tmax and Tmin, may be calculated as the sum of the four highest and the sum of the four lowest of the emitter discharge times evaluated, respectively. The application examples showed that the uniformity coefficient of the irrigation system can be determined using a chart or a simple equation, and also noted that as the value of the uniformity coefficient declined, the error has increased, corroborating with the prerogative of that must analyze possible causes of decreased system uniformity when CU values are less than 80%.

Obstrução e uniformidade de aplicação em sistemas de irrigação por gotejamento aplicando-se efluente da suinocultura

Neste trabalho buscou-se analisar o efeito de diferentes manejos de água residuária de suinocultura e de água de abastecimento na obstrução de emissores e na uniformidade de aplicação de sistemas de irrigação por gotejamento. O experimento foi realizado na Universidade Federal de Viçosa (UFV) e montado em esquema de parcelas subsubdivididas tendo, nas parcelas, os manejos (1E3A - uma hora de aplicação de efluente mais três horas de aplicação de água limpa, 2E2A - duas horas de aplicação de efluente mais duas horas de aplicação de água limpa, 3E1A - três horas de aplicação de efluente mais uma hora de aplicação de água limpa e 4E - quatro horas de aplicação de efluente), nas subparcelas os tipos de gotejador (G1, G2 e G3) e, nas subsubparcelas, os tempos das avaliações (0, 20, 40, 60, 80, 100, 120, 140 e 160 h) em delineamento inteiramente casualizado com três repetições. Os resultados obtidos indicaram que na água residuária de suinocultura as características sólidos suspensos, ferro total e população bacteriana, representaram risco severo de entupimento de gotejadores e que houve redução elevada da uniformidade de aplicação de efluente quando o tempo de aplicação de água residuária foi igual ou superior ao da água de abastecimento.

Effects of Drip System Uniformity and Irrigation Amount on Water and Salt Distributions in Soil Under Arid Conditions

The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients (CU) of approximately 65, 80, and 95% (referred to as low, medium, and high uniformity, respectively) and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity (ECb) was monitored continuously with approximately equally spaced frequency domain reflectometry (FDR) sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.