Original Article
Pressurized Irrigation Systems
Mustafa Goodarzi; Saber Zolfaghari
Abstract
Extended AbstractIntroductionPressurized irrigation systems are increasingly used to improve water management and reduce water losses in agricultural production, particularly in regions facing water scarcity. However, the expected benefits of these systems cannot be achieved solely through appropriate ...
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Extended AbstractIntroductionPressurized irrigation systems are increasingly used to improve water management and reduce water losses in agricultural production, particularly in regions facing water scarcity. However, the expected benefits of these systems cannot be achieved solely through appropriate design and installation. Their long-term performance also depends on proper operation, preventive maintenance, timely technical support, and continuous monitoring during the service life of the system. Inadequate operation and maintenance may gradually alter hydraulic conditions, reduce the effectiveness of water application, and lead to deterioration in the overall condition of irrigation systems. In addition, farmers and system operators need adequate technical knowledge and continued access to professional support to maintain the systems under field conditions. The objective of this study was to evaluate changes in selected technical indicators of pressurized irrigation systems following the implementation of an operation and maintenance monitoring program and to assess farmers’ perceptions of the factors contributing to successful long-term operation and maintenance of these systems.MethodologyThe study was conducted in Arak and Shazand counties of Markazi Province, Iran. A total of 30 pressurized irrigation systems were selected for field evaluation, including 20 systems in Arak and 10 systems in Shazand. The systems were evaluated repeatedly at four measurement stages consisting of the initial technical supervision stage and three subsequent follow-up stages during the cropping season. Two field-based technical indicators were used to assess the condition of the irrigation systems: operating pressure and soil water content. Operating pressure was measured using a pressure gauge and expressed as meters of water head. These two indicators were selected because operating pressure provides an important indication of the hydraulic operating condition of pressurized irrigation systems, while soil water content provides information about the resulting moisture condition of the root-zone soil following irrigation. In addition to the field measurements, a structured questionnaire was administered to the operators of the evaluated irrigation systems. The questionnaire consisted of 24 items and was designed to assess farmers’ perceptions of factors affecting the successful operation and maintenance of pressurized irrigation systems. Responses were recorded using a five-point Likert scale. The content of the questionnaire was reviewed by experts in irrigation and operation and maintenance of pressurized irrigation systems. Field data were analyzed using descriptive statistics and repeated-measures analysis of variance. Measurement stage was considered the within-system factor, whereas county was considered the between-system factor. Where appropriate, pairwise comparisons were conducted using Bonferroni adjustment to control the probability of Type I error associated with multiple comparisons.Results and Discussion The results showed that the mean operating pressure of the evaluated irrigation systems was 42.33 m of water head at the initial technical supervision stage. The corresponding values at the first, second, and third follow-up stages were 39.73, 40.30, and 39.97 m, respectively. Thus, operating pressure showed an overall decline after the initial supervision stage, although the values remained relatively stable across the three subsequent follow-up stages. Repeated-measures analysis indicated a statistically significant effect of measurement stage on operating pressure, demonstrating that operating pressure changed over the monitoring period. However, the overall difference between Arak and Shazand counties was not statistically significant. Bonferroni-adjusted pairwise comparisons showed that the pressure at the initial supervision stage was significantly higher than the pressure recorded at the second and third follow-up stages. In contrast, the difference between the initial supervision stage and the first follow-up stage was not statistically significant. Furthermore, none of the differences among the three follow-up stages was statistically significant. These results suggest that although some reduction in operating pressure occurred following the initial supervision, the pressure conditions were comparatively stable during the subsequent monitoring stages.Soil water content also showed an overall declining tendency. The mean soil water content decreased from 27.51% at the initial supervision stage to 26.47%, 26.83%, and 25.72% at the first, second, and third follow-up stages, respectively. The repeated-measures analysis showed no statistically significant overall difference between Arak and Shazand counties. The results therefore indicate that the general temporal pattern of soil water content was similar in the two counties. Bonferroni-adjusted pairwise comparisons indicated that the significant difference was primarily observed between the initial supervision stage and the first follow-up stage, whereas the subsequent pairwise differences were not statistically significant. An important finding was the increase in variability in soil water content toward the third follow-up stage. This increase may indicate greater heterogeneity among irrigation systems or differences in management conditions among operators. However, because spatial variability, irrigation discharge, application uniformity, and detailed soil characteristics were not independently evaluated, the underlying causes of this variability cannot be determined from the present data.The questionnaire results provided complementary information concerning farmers’ perceptions of operation and maintenance. The highest percentage score was obtained for operation management (83.33%), followed by technical recommendations (70.33%). The scores for operator training, increased productivity, and water saving were 56.67%, 46.67%, and 41.33%, respectively. These results indicate relatively high perceived performance in operation management and technical recommendations, while training, productivity, and water saving received comparatively lower scores.ConclusionsThe findings indicate that the operation and maintenance monitoring program was associated with relatively stable hydraulic and soil-moisture conditions during the follow-up period, although both operating pressure and soil water content showed an overall declining tendency after the initial supervision stage. The results support the importance of moving from a one-time supervision approach toward a continuous operation and maintenance support system. Periodic technical inspections, follow-up visits, preventive maintenance, operator training, and routine monitoring of key indicators such as operating pressure and soil water content can help identify potential changes in system condition at an early stage. Nevertheless, because the study did not include an independent control group and did not directly measure indicators such as discharge, distribution uniformity, application efficiency, or water productivity, the findings should be interpreted as evidence of changes in selected technical indicators rather than direct proof of improvements in overall irrigation efficiency. Future studies should incorporate a broader range of hydraulic, agronomic, and economic indicators and, where possible, include control systems to provide stronger evidence regarding the causal effectiveness of continuous monitoring and technical supervision programs. Conflict of InterestThe authors declared no potential conflicts of interest concerning the research, authorship, and publication of this article. FundingThe authors received no financial support for the research, authorship, and publication of this article. Data Availability StatementsAll relevant data and results supporting the findings of this study are presented within the article. The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. Author ContributionAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors. All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.AcknowledgementThe authors sincerely appreciate the cooperation and assistance of the farmers and irrigation-system operators who participated in this study, the technical experts and supervisors of the pressurized irrigation systems, and the management and technical staff of Arak and Shazand agricultural jihad centers for their valuable support during the fieldwork and data collection.
Original Article
Pressurized Irrigation Systems
Zahra Mahdian; Abdolmajid Liaghat; Farhad Mirzaei; Armin Hasanzadeh
Abstract
Extended AbstractIntroductionWater scarcity in arid and semi-arid regions has increased the need for irrigation technologies that improve water-use efficiency while minimizing water losses. Subsurface irrigation delivers water directly to the root zone through buried emitters, thereby reducing surface ...
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Extended AbstractIntroductionWater scarcity in arid and semi-arid regions has increased the need for irrigation technologies that improve water-use efficiency while minimizing water losses. Subsurface irrigation delivers water directly to the root zone through buried emitters, thereby reducing surface evaporation and runoff. PVC cylinder–based subsurface irrigation systems have attracted attention because of their simple design, low cost, and adaptability. However, the medium surrounding the cylinder can strongly influence water transfer into the soil and, consequently, the geometry and temporal development of the wetting bulb. Differences in porosity, hydraulic conductivity, pore structure, and water-retention capacity among surrounding media may alter water-flow pathways and wetting patterns. Therefore, this study investigated the effects of eight surrounding media on wetting-bulb depth, width, area, and volume at 1, 3, and 7 days after irrigation.MethodologyThe experiment was conducted at the research station of the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, using a silty clay loam soil (30% clay, 56% silt, and 14% sand), with a bulk density of 1.13 g cm⁻³ and total porosity of 47%. The antecedent soil water content was 0.07 cm³ cm⁻³ for all treatments. Perforated PVC cylinders (6 cm internal diameter and 55 cm length) were installed vertically to a depth of 50 cm, leaving 5 cm above the soil surface for connection to a bubbler emitter. Each cylinder had eight outlet perforations distributed at four depths (10, 20, 30, and 40 cm), with perforation diameters determined using an orifice-flow relationship to achieve uniform discharge. Eight surrounding media—aeolian sand, agricultural pumice, local soil (control), perlite, pea gravel, non-woven geotextile, vermicompost, and cocopeat—were evaluated, with one PVC cylinder used for each treatment. Each treatment received a single 100-L irrigation application at an inlet pressure of 0.1 bar. Wetting-bulb development was monitored using the trench method. The same trench was progressively extended at 1, 3, and 7 days after irrigation to expose the advancing wetting front while avoiding repeated backfilling and re-excavation that could disturb soil structure and preferential flow pathways. To minimize evaporative losses from the exposed soil surface, the trench was covered with a plastic sheet between successive observations. Wetted-zone boundaries were traced and digitized in AutoCAD, and two-dimensional and three-dimensional reconstructions were used to determine wetting-bulb depth, width, area, and volume.Results and DiscussionBecause one PVC cylinder was used for each treatment, the results represent observed differences rather than statistically tested treatment effects. Vermicompost and non-woven geotextile progressively restricted outlet flow, causing an inflow–outflow mismatch and water overflow; consequently, both were excluded from further analysis. Among the remaining six media, perlite produced the most balanced wetting pattern and the greatest wetted area and volume. By day 7, its wetted area and volume reached 5,227 cm² and 348,877 cm³, representing increases of approximately 50% and 80%, respectively, relative to day 1. This performance may be associated with its high porosity, low bulk density, and favorable hydraulic properties, which could facilitate lateral and vertical water redistribution. Agricultural pumice produced the greatest wetting depth, suggesting that its coarse and heterogeneous pore structure may have promoted greater vertical redistribution. Thus, pore-size distribution and pore continuity, in addition to hydraulic conductivity, may influence dominant flow pathways. Aeolian sand and pea gravel exhibited relatively rapid initial wetting but limited subsequent expansion. By day 7, wetted area and volume had increased by approximately 24% and 29% for sand and 32% and 50% for gravel, respectively. The local-soil control produced a more restricted wetting bulb than most amended media. Cocopeat showed the most limited initial wetting but the greatest relative expansion over time, with wetted area and volume increasing by approximately 153% and 205%, respectively, by day 7. This behavior may be related to its fibrous structure and high water-retention capacity, which can support gradual redistribution of stored water.ConclusionsThe surrounding medium strongly influences the hydraulic performance and geometric and temporal development of wetting bulbs in PVC cylinder–based subsurface irrigation. Vermicompost and non-woven geotextile may be unsuitable for direct placement around concentrated outlets because they restricted discharge and caused overflow. Among the functional media, perlite produced the greatest wetted area and volume and the most balanced wetting pattern, whereas agricultural pumice resulted in the greatest wetting depth. Cocopeat, despite limited initial wetting, exhibited the greatest relative expansion over time, indicating potential for gradual water redistribution. Therefore, surrounding-medium selection should consider the intended hydraulic function—maximizing wetted volume and spatial coverage or promoting gradual redistribution—rather than relying on a single hydraulic property such as saturated hydraulic conductivity. These findings are limited to the tested soil texture, irrigation volume, discharge conditions, seven-day observation period, and single-cylinder design. Further studies using multiple replicates, different soil textures, and non-destructive moisture monitoring are recommended. AcknowledgmentsThe authors would like to express their sincere appreciation to the Editor-in-Chief and the anonymous reviewers for their valuable time, thorough evaluation, and insightful comments and suggestions. Their constructive feedback substantially contributed to improving the scientific quality, methodological rigor, structural organization, and overall clarity of this manuscript.Conflict of InterestThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.FundingThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.Data Availability StatementsThe datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. Authors’ ContributionsAll authors contributed equally to the conceptualization of the research problem and to the preparation of both the original draft and the final version of the manuscript. Z.M. was responsible for the methodology, literature review, execution of the research, data collection, data analysis, and preparation of the preliminary draft of the results section. A.H. contributed to the implementation of the experimental work, including laboratory and field experiments, as well as data collection. A.L. and F.M.A.S. jointly supervised the research, validated the findings, provided the facilities and resources required for the study, and critically reviewed and edited the manuscript. All four authors contributed to the conceptualization of the research problem, participated in preparing the original and subsequent drafts of the manuscript, and have read and approved the final published version.
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