Original Article
Pressurized Irrigation Systems
Nader Naderi; Alireza Mohammadi
Abstract
IntroductionFood security and increasing self-reliance in basic crops are important pillars of the country's economic development plans. One of the most important challenges to this self-reliance is the low water productivity in the strategic crop of wheat. An effective and practical solution is to use ...
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IntroductionFood security and increasing self-reliance in basic crops are important pillars of the country's economic development plans. One of the most important challenges to this self-reliance is the low water productivity in the strategic crop of wheat. An effective and practical solution is to use water optimally and save it. Pressure irrigation increases applied water efficiency by preventing water waste. The advantages of irrigation with the Rainflat system include reduced initial annual irrigation costs compared to the drip tape irrigation method, quick and easy installation without the need for welding, easy and quick assembly and reinstallation, no need for specialized personnel and special tools for installation and assembly, and the ability to use it to irrigate multiple fields. The water productivity index is used to evaluate optimal water consumption in analyses and decision-making. This index is affected by the irrigation schedule. An irrigation schedule is the amount of crop water requirement that is provided to the crop through irrigation intervals. It is believed that if the crop water requirement is used correctly and appropriately in modern irrigation methods, in addition to reducing costs, it is possible to save water consumption by increasing irrigation efficiency and help strengthen groundwater aquifers. Therefore, this study was conducted to investigate the effect of irrigation intervals and different amounts of water in the rain flat sprinkler irrigation method on wheat yield and water productivity.
Methodology This study was conducted in order to investigate the effect of irrigation interval and irrigation water amount on yield and water productivity of wheat in the years 2019 to 2021 in the form of split plots experiment based on randomized complete blocks design in three replications. The experiment was carried out in agriculture research and education center of Semnan (Shahrud). The soil texture was sandy loam. The main plots included 3 irrigation intervals (4, 5 and 6 days) and the sub-plots included three levels of irrigation (100, 80 and 60%). Sprinkler irrigation pipes (laterals) were placed at 4-meter intervals between crop rows. The net irrigation water requirement was calculated using the Penman-Monteith method and at the end, the amount of water consumption, wheat yield, and water productivity were determined and the best treatment was identified.
Results and Discussion Irrigation interval treatments of 4 and 5 days with grain yield of 5410.6 and 5016.1 kg/ha and water productivity of 1.169 and 1.077 kg/m3 were in the superior statistical group. The treatments of 100 and 80 percent irrigation requirement with average yields of 5520.7 and 5218.4 kg/ha had the highest yield, and the treatment of 80 percent irrigation requirement with water productivity of 1.130 kg/m3 had the highest water productivity. The interaction effect of experimental treatments on the studied traits was effective. Thus, the treatments of 4-day irrigation interval with 100% and 80% water requirement and 5-day irrigation interval with 100% water requirement were superior with grain yields of 6352.4, 6172.5, and 6105.5 kg/ha, respectively. The 4-day irrigation interval with 80% water requirement had the highest water productivity of 1.336 kg/m3.
Conclusions The results showed that in the rain flat irrigation method, increasing the irrigation interval to 6 days compared to the irrigation interval of 4 and 5 days reduced the yield by 35.55 and 30.48 percent and water productivity by 35.55 and 29.61 percent. Because the irrigation interval treatments of 4 and 5 days were in the superior statistical group in terms of yield and water productivity, the best irrigation interval is 5 days. By reducing the percentage of irrigation water supply to 60% of the water requirement, compared to 80 and 100% of the water requirement, yield decreased by 39.17 and 42.50%, respectively. However, in terms of water productivity, the treatment of 80% irrigation requirement with an average water productivity of 1.130 kg/m3 had the highest water productivity and was placed in the superior statistical group. Although the treatment with a 4-day irrigation interval with 80% water requirement did not have a statistically significant difference in yield compared to the 4- and 5-day irrigation intervals with 100% water requirement. but it had the highest water productivity among the irrigation treatments. Therefore, with the rain flat irrigation method, the percentage of water requirement can be reduced by 20% in the 4-day irrigation interval.
technical paper
Nader Heydari; Farshid Taran
Abstract
The concept of virtual water has been highlighted in the 21st century as a key indicator to evaluate the optimal use of water in the production of agricultural products, especially in the face of the water shortage crisis. This study analyzed the virtual water of irrigated wheat, known as one of the ...
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The concept of virtual water has been highlighted in the 21st century as a key indicator to evaluate the optimal use of water in the production of agricultural products, especially in the face of the water shortage crisis. This study analyzed the virtual water of irrigated wheat, known as one of the strategic agricultural products, in Iran and investigated the differences in the amount of virtual water of irrigated wheat in different provinces and climates of the country. The results indicated that the amount of virtual water of irrigated wheat in Iran is in a wide range of 284-3523 m3 ton-1 with an average of 1400 m3 ton-1, being 50% higher than the average values found in a number of other countries (930 m3 ton-1). The highest amount of virtual water (1539-3523 m3 ton-1) is in the provinces of Khuzestan, Kerman, Semnan, Bushehr, Sistan and Baluchestan, Isfahan, Fars, Yazd, some areas of Qom, Kermanshah, South Khorasan, North Khorasan, Chaharmahal and Bakhtiari, and East Azarbaijan with an average of 2610 m3 ton-1. Also, the lowest amount of virtual water (284-586 m3 ton-1) can be seen in the provinces of Mazandaran, Hamedan, Golestan, Kordestan, Kohkiluyeh and Buyer Ahmad, some areas of South Khorasan, Markazi, Hormozgan, and Ilam with an average of 451 m3 ton-1. The study showed that most of the areas under cultivation of wheat in Iran (about 53% of the irrigated wheat lands) are located in areas with water shortage crisis. The advantage of wheat cultivation in terms of water requirement and water use efficiency varies in different provinces. In terms of virtual water content, wheat cultivation is suitable in two provinces of Golestan and Ardabil, which relatively do not have water shortage problems and have low virtual water content of irrigated wheat. Khuzestan province also is preferable for wheat cultivation if the irrigation management is improved, due to the suitable climate and warm weather and the possibility of using winter rains in the growing season and quick ripening of the crop. But, wheat cultivation is not suitable in some regions of Iran, especially in the central and southeastern regions. The results of this study emphasize the necessity of optimal management of agricultural water resources and the strategic selection of areas under wheat cultivation based on the national cropping pattern from the aspect of advantage of production related to water requirements, water resource limitations, improving productivity and reducing virtual water content, reducing of crop wastes, and more attention on virtual water trade of wheat.
Original Article
Maryam Navabian; Mostafa Jamshidi Avanaki
Abstract
Extended AbstractIntroductionKnowledge of soil moisture status can significantly impact irrigation planning and, consequently, water management in the agricultural sector, which is the most expensive recipient of water resource allocation. Soil moisture measurement using the porous block method, based ...
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Extended AbstractIntroductionKnowledge of soil moisture status can significantly impact irrigation planning and, consequently, water management in the agricultural sector, which is the most expensive recipient of water resource allocation. Soil moisture measurement using the porous block method, based on electrical resistance measurement, is one of the techniques for assessing moisture levels. Developing an understanding of its construction can effectively reduce costs, increase accuracy, simplify moisture measurement, and achieve these goals. This study aims to enhance the understanding of soil moisture measurement through the development and assessment of porous blocks constructed with glass mat fibers, specifically P200 and P186 types.Materials and MethodsIn this regard, two types of glass fibers, P200 and P186, were used in the construction of a block with a fibrous structure. The accuracy of moisture measurement was then evaluated in 10 different soil textures. To prepare the soil, it was dried, pounded, and passed through a 2-mm sieve before being placed into a pot. After installing three replicates of each block in the pot, the soil was saturated. At various intervals until the soil dried, the electrical resistance of the block and the soil moisture were measured using the gravimetric method. To assess the accuracy of the blocks, the moisture readings from the blocks were compared with those obtained from the gravimetric method, and statistical indices such as R² (coefficient of determination), RMSE (root mean square error), nRMSE (normalized root mean square error), MAE (mean absolute error), and D-index (index of agreement) were calculated.Results and DiscussionThe results showed that ELE glass fibers absorbed 2.6 and 0.5 times more water than P200 and P186 fibers, respectively, over 180 seconds. A comparison of the fitting curves for the wicking behavior of the two fibers indicates that the quadratic curve provides a better fit than the linear curve. Additionally, the results showed that solution absorption in P186 decreased earlier than in P200. Therefore, it appears that P200 fibers are more effective at absorbing the solution and, subsequently, the water from the soil environment. The results also indicated that ELE and P200 fibers exhibited a similar decreasing trend in moisture over the first 15 minutes; however, after that point, the moisture reduction rate in P200 continued at a lower slope. P200 fibers demonstrated behavior more akin to ELE fibers during both moisture reduction and solution absorption. The findings reveal that the porous blocks constructed with P200 fibers achieved superior accuracy in measuring soil moisture, yielding an error margin of approximately 5%. Notably, the findings indicate that the P186 and P200 fibers exhibit optimal accuracy in medium soil textures, outperforming their performance in other soil types. Specifically, the P186 fibers achieve their highest accuracy in soil textures characterized by a sand content between 50-70% and clay content below 35%. Similarly, the P200 fibers also demonstrate robust accuracy within the same sand and clay content ranges, but they extend their effectiveness to include soils with sand content ranging from 20-50% and clay content around 28%. Conversely, the results suggest that both P200 and P186 fibers struggle with accuracy in soil textures that exhibit either high clay or high sand content. This highlights the importance of soil composition in the performance of these fibers for measuring soil moisture, indicating that they are less reliable in extreme soil conditions. Furthermore, the study highlighted a decline in measurement accuracy at elevated soil moisture levels, indicating that these blocks are most effective within a soil moisture range of 25-40% by weight.ConclusionIn conclusion, this research underscores the potential of utilizing glass mat fibers in the construction of porous blocks to improve soil moisture measurement accuracy. By refining this methodology, the findings contribute valuable insights toward optimizing irrigation practices and advancing water management strategies in agriculture. Enhanced accuracy in moisture readings not only promotes efficient water usage but also supports sustainable agricultural practices, ultimately benefiting food production and environmental conservation efforts.
Original Article
Irrigation network management
Abdolrahman Mirzaei; Afshin Soltani; Fariborz Abbasi; Ebrahim Zeinali; Shahrzad Mirkarimi
Abstract
Introduction
Over-withdrawal of water in the agricultural sector of Iran is one of the most important factors that threatens the sustainability of agricultural production and natural resources. Therefore, appropriate approaches should be used to eliminate this factor. In this ...
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Introduction
Over-withdrawal of water in the agricultural sector of Iran is one of the most important factors that threatens the sustainability of agricultural production and natural resources. Therefore, appropriate approaches should be used to eliminate this factor. In this study, the water saving capacity in the irrigated agricultural sector of Fars province was examined using some options that decrease irrigation demand in fields and orchards. These options are: (1) optimization of cropping pattern with the aim of minimizing water use, (2) using shade net in gardens and vegetable farms, (3) using straw mulch in gardens and farms though implementation of conservation tillage, (4) changing the current flooded rice cultivation system to aerobic system, and (5) transferring vegetable production from the farm to the greenhouse. The effects of the options were assessed individually and in combination.
Methodology
The System for regional Agricultural Water balance and Accounting (SAWA) set up for irrigated agriculture lands in Fars province was used. The core of this system consists of a plant simulation model (SSM-iCrop2). For each of the water saving option of this study, a separate SAWA system was prepared and the amount of irrigation water used in agriculture in the province was estimated and compared. The system provides crop yield and irrigation water under farmer’s and potential conditions as influenced by climate, soil, management and crop. The system estimates were based on 10-year meteorological data (2011-2021), 5-year average crop area statistics (2017-2021), and yield, price, and cost of production data for plants in 2021.
Results and Discussion
The results showed that the applied irrigation water in agriculture in the province for farmers' conditions (not for potential or optimal conditions) under the current cropping pattern is 4619 million cubic meters per year (net irrigation water without considering irrigation efficiency and uneven water distribution). Optimization of the cropping pattern reduced this figure by 35% (a reduction equivalent to 1616 million cubic meters per year). Optimizing the cropping pattern was done with the aim of minimizing the amount of irrigation water applied under farmers' conditions in the entire province provided that the farmers profits in the optimized pattern would not change and the area under cultivation of perennial plants and legumes, which play an important role in agricultural sustainability, would not decrease.The implementation of 2 t/ha straw mulch vias conservation tillage for all crops except for rice and alfalafa in the current and optimal cropping patterns reduced the net applied water by 8 and 10%, respectively (equivalent to 384 and 292 million cubic meters per year), the use of shade net (decreases solar radiation by 50%) during the summer months in the current and optimal cropping patterns reduced the applied water by 29 and 24%, respectively (equivalent to 1331 and 713 million cubic meters per year), and the use of aerobic rice cultivation system instead of flooding system in the current and optimal cropping patterns reduced the applied water by 4 and 1%, respectively (equivalent to 185 and 37 million cubic meters per year). Transferring vegetable production from the field to the greenhouse in both the current and optimal cultivation patterns was able to reduce the applied irrigation water by 4 percent (equivalent to 167 and 137 million cubic meters per year, respectively). However, combination of water saving options in the current and optimal cropping patterns could save irrigation water by 66 and 48% (equivalent to 3048 and 1444 million cubic meters per year), respectively.
Conclusions
The findings of this study indicate that the evaluated options provide safe and effective solutions for addressing water scarcity in the irrigated agriculture of Fars Province. Therefore, it is recommended that executive officials, policymakers, and agricultural sector stakeholders work toward eliminating barriers and promoting the widespread adoption of these valuable options through evaluation and additional studies. By doing so, sustainable agricultural practices can be achieved, contributing to a healthier environment and preventing further ecological degradation.
Original Article
River engineering
Saeb Alghezi; Javad Mozaffari
Abstract
Introduction
Labyrinth weirs have a longer length than linear weirs and therefore pass more flow in the fixed width of the channel. Investigating a labyrinth weir with the highest efficiency at a fixed width can help reduce construction costs and also allow flow to pass at a lower height. However, investigating ...
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Introduction
Labyrinth weirs have a longer length than linear weirs and therefore pass more flow in the fixed width of the channel. Investigating a labyrinth weir with the highest efficiency at a fixed width can help reduce construction costs and also allow flow to pass at a lower height. However, investigating physical models to determine a labyrinth weir with a more appropriate efficiency will be costly. While using simulation software,
in addition to reducing costs, allows for the creation of different labyrinth weir shapes in the software. The discharge coefficient of a labyrinth weir is affected by various parameters, one of which is the apex ratio. These parameters can be effective on the nappe interference, local submergence, and the creation of turbulence in the flow. In this study, the effect of different apex ratios in a labyrinth weir will be investigated.
Methodology
In this research, the flow in triangular and trapezoidal Labyrinth weir was investigated using FLOW 3D software and RNG k-ε model.To investigate the effect of the apex ratio, nine labyrith weir models were simulated with magnification ratios L⁄W=2, L⁄W=3, and L⁄W=4. Three triangular labyrith weir models with an apex ratio of zero, three trapezoidal labyrith weir models with an apex ratio of 0.125, and three trapezoidal labyrith weir models with an apex ratio of 0.250 were simulated. Also, to investigate the effect of the weir wall angle with the channel wall, a trapezoidal labyrith weir model with an apex ratio of 0.25 on the side was investigated.
Results and Discussion
Investigations showed that with an increase in the water head ratio (HT⁄P) and also with an increase in the magnification ratio, the local submergence and the nappe interference increases and causes a decrease in the discharge coefficient in the triangular and trapezoidal labyrinth weir. Although it seems that the greater distance between the two sides of the trapezoidal labyrinth weir at the apex compared to each other, caused a decrease in local submergence and an increase in the discharge coefficient, but the results showed that the triangular labyrinth weir had a better performance. By increasing the apex width up to 20 cm in a trapezoidal weir, a larger area will be created upstream of the weir apex with a lower velocity and more turbulence will be created in the flow near the apex. On the other hand, creating a lower velocity at the apex will cause the flow to move to the sides, which will cause the flow to move to the sides and create more turbulence on the sides and will reduce the discharge coefficient. Also, the results showed that trapezoidal labyrinth weir with apex width on the sides had lower performance because the amount of nappe interference and local submergence at the apex will be higher.
Conclusions
The study of the k-ε RNG turbulence model and comparison with laboratory data showed that the model used had acceptable accuracy in simulation. Increasing the water head ratio has caused a decrease in the discharge coefficient in the weir in all models. The reason is the increase in local submergence and napee interference. Local submergence causes the effective length of the labyrinet weir to decrease. Also, the nappe interference causes resistance to the flow and reduces the discharge coefficient. Increasing the magnification ratio causes more nappe interference and local submergence at downstream of weir and causes transverse curvature in the flow and collision of transverse jets and creates turbulence at upstream of weir. As a result, these factors will cause a decrease in the discharge coefficient. At the same magnification ratios, the trapezoidal labyrinth weir has a lower efficiency than the triangular labyrinth weir. It seems that although the nappe interference and local submergence at the apex of the trapezoidal labyrinet weir has decreased, the perpendicularity of the flow at the apex to the weir wall will cause more turbulence and reduce performance.
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