M. Arabfard; A. Shahnazari; Mirkhaleg Ziatabar Ahmadi
Abstract
Introduction: Practical problems such as rushing roots toward pot, difficulty of manually filling with water and deficit irrigation due to permeation from regular pots prevents the development of pot irrigation. With regard to increasing irrigation efficiency importance and preventing water loss to fix ...
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Introduction: Practical problems such as rushing roots toward pot, difficulty of manually filling with water and deficit irrigation due to permeation from regular pots prevents the development of pot irrigation. With regard to increasing irrigation efficiency importance and preventing water loss to fix the problems of this irrigation method.Changing physical structure of pot could solve many problems and issues which this irrigation technique is facing. Comparison of the two major characteristics of localized irrigation hydraulic characteristics (coefficient of variation and distribution uniformity) and also using gravity pressure can achieve a solution for water and energy shortage problems. So far, with knowledge of the role of water pressure at gravitational pressures in hydraulicproperties of these methods, some effective features in these methods application is specified.
Material and Methods: This study was carried out in randomized complete block at water engineering department of Sari Agriculture Science and Natural Resources university laboratory from September to December 2015. In this study, in the form of randomized complete block, hydraulic specifications of three treatments of pot irrigation, gravity drip irrigation and porous pipe irrigation investigated under water pressure of 0.5, 1.5 and 3 m. In each of the water column pressure, output water volume from 10 samples of each irrigation method treatments calculated from 7 replicates during one hour in about two months. Porous pipes which used in this study were imported 16mm sample pipes from Anahita Company. GDI gravitational emitter model, porous pipe and containers made of cellulose clay pots in the form of cylinder shape with diameter of 15 cm were used. Thus, within one hour of irrigation, water volume withdrawn from tested samples under constant pressure of irrigation were collected by suitable containers and measured by graded container and flow rate of each samples were calculated. Christensen distribution uniformity coefficient was calculated with Christensen distribution uniformity coefficient formula. Based on USA agronomical engineers, a pointed emitters with variation coefficient less than 0.05 is good, with cv of 0.05-0.10 is medium and with cv of 0.10-0.15 is weak. After calculating evaluation parameters, the results were analyzed with SPSS statistical software and Tukey test at 1 %and 5 % level of probability.
Results and Discussion: The results of statistical analysis of randomized complete block design and mean comparison of different level of treatments effects with Duncan test (irrigation method treatment and water pressure treatment) at 5 %level of probability showed that maximum distribution uniformity achieved in gravitational drip irrigation among samples. With increasing pressure, coefficient of variation was less affected and at lower pressures, coefficient of variation among tested samples were more evident. In addition, it is indicated that increasing pressure have maximum effect on flow rate and distribution uniformity increment while with increasing pressure, minimum changes observed in coefficient of variation. Therefore, among possible gravitational pressures in each project, maximum pressure should be selected for design and implementation. Result showed that in porous pipes and in pressures of 50, 150 and 300 cm, average flow rate were 0.31, 1.4 and 4.2 liter per hour in meter, average coefficient of variation were 0.88, 0.61 and 0.83 and average distribution uniformity were 2.2, 6.2 and 1.6 percent, respectively. In the main-treatment and in each pressure sub-treatment, samples flow rate changes at different replicates is so high that coefficient of variation was more than conventional coefficient (more than 0.6) and thus classified in unacceptable emitters. In this treatment, distribution uniformity was so low that using this irrigation method at gravitational pressures range cannot be recommended. Based on statistical analysis results, it is indicated that increasing pressure in gravitational drip irrigation have maximum effect and in pot irrigation, have minimum effect on flow rate changes, and in addition, maximum distribution uniformity among samples was in gravitational drip irrigation while in porous pipe irrigation besides high coefficient of variation, minimum distribution uniformity among samples were observed.
Conclusion: Due to the high influence of pressure changes in gravitational pressures on hydraulic characteristics of mentioned three irrigation method, among investigated gravitational pressures in this study, pressure of 3m as appropriate pressure at gravitational pressures and among localized irrigation methods, gravitational drip irrigation were recommended. It is recommended to paying attention to the development of gravitational drip irrigation application in large-scale garden and agriculture projects with positive approach.
shahrzad gharcheh; M. Delbari; F. Ganji
Abstract
Introduction: An appropriate water resources management and planning is necessary due to the scarcity of water resources and rapidly growing world population. In this regard, selecting appropriate methods for irrigation is one of the most important issues. Drip irrigation is a recent advanced irrigation ...
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Introduction: An appropriate water resources management and planning is necessary due to the scarcity of water resources and rapidly growing world population. In this regard, selecting appropriate methods for irrigation is one of the most important issues. Drip irrigation is a recent advanced irrigation method in which fertilizers can be efficiently applied along with irrigation water. Drip fertigation, however, can potentially cause clogging of emitters. Various factors such as clogging increase manufactures’ coefficient of variation and water temperature and pressure changes could alter emitter discharge and water distribution uniformity. The aim of this study is to evaluate the effect of fertigation on clogging of emitters and the performance of drip irrigation systems.
Materials and Methods: This study was performed as a laboratory experiment at the University of Zabol. The experiment was done in the form of factorial in a completely randomized design with three replications in the hydraulics laboratory, the University of Zabol. The first factor was fertilizer type including: F0 (control), F1 (ammonium nitrate) and F2 (urea) and the second factor was the emitter types including one-nozzle on line (A), six-nozzles in line (B) and eight-nozzles on line (C). The tap water was used for irrigation. The system included 9 laterals, 3 m each with 18 emitters on each lateral. Fertilizer solution with known concentrations of 0.08 grams per liter was entered into the system from a plastic tank. Fertilizer tank was covered to avoid water evaporation even in a small amount. The experiment lasted for 60 days with 12 operating hours per day. The emitter discharge was measured every three days at the end of day. In order to evaluate the degree of emitter clogging, the percentages of discharge reduction (Qt), Christiansen’s coefficient of uniformity (CU), distribution uniformity (DU) and discharge coefficient of variations (Vm) were calculated as follows:
(1)
(2)
(3)
(4)
where qa, qm and qt are the average, primary and secondary emitter discharges (L/hrs), respectively, qi is the individual emitter discharge (L/hrs), Sm is the standard deviation of discharge (L/hrs) and n is the number of measurements.
Results and Discussion: The results indicated that both fertilizer and emitter type have significant effect on reduction of emitter discharge and distribution uniformity as well as on increase of emitter coefficient of variation. The Duncan test for comparing means showed that the A type emitters had the highest clogging while the B type emitters had the lowest clogging. The percentages of discharge reduction for emitters A, B and C were about 18, 24 and 22, respectively, for treatment F0 (control); 24, 39 and 30 for treatment F1; and 34, 44 and 32 for treatment F2. The results indicated that the emitter clogging increases with altering fertilizer from F0 to F2. F2 (urea fertilizer) had the worse effect on emitter clogging than F1 (ammonium nitrate fertilizer) which could be due to more nitrate produced by urea fertilizer. Also, the results showed that the emitter clogging and discharge coefficient of variation are increased by increasing the elapsed time. Urea and ammonium nitrate fertilizers are hydrolyzed in water and partly converted to nitrate, which is consumed by algae and other microorganisms causing slime accumulation. Bacterial slimes can be a direct cause of clogging for emitters.
Conclusion: According to the results, both fertilizer and emitter types may significantly change the hydraulic properties of emitters. The smallest clogging belonged to emitter of type A when fertilizer F0 was applied as it results in discharge reduction of 18.44%. The largest clogging belonged to emitter of type B when fertilizer F2 was applied (discharge reduction was about 44%). In general, it could be said that fertigation may influence emitter discharge depending on fertilizer treatments (e.g. fertilizer type and concentration), water properties and emitter type. The clogging problems must be attended more specifically as it may reduce farmers’ willingness for drip irrigation implementation and makes them do surface irrigation which may result in more water losses. This study showed that the quality of water used in drip fertigation increases the clogging made by fertilizer application. So, the quality of irrigation water should be investigated every few days. The use of nitrogen fertilizer may cause biological clogging of emitters, so when such fertilizer are used, the type of emitter should be considered.
