b k; f m; t s
Abstract
Drip irrigation has a priority in selecting an appropriate irrigation method in arid and semi-arid regions because of its potential of precisely applying water and chemicals both in quantity and position. Proper design and management of a drip fertigation system is, to some extent, dependent upon a better ...
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Drip irrigation has a priority in selecting an appropriate irrigation method in arid and semi-arid regions because of its potential of precisely applying water and chemicals both in quantity and position. Proper design and management of a drip fertigation system is, to some extent, dependent upon a better understanding of wetting patterns and water and solute distributions in soil under different combinations of soil type and layering, emitter application rate, volume applied and fertigation concentration. In this study, experiments were carried out in a transparent plexiglass tank (0.5 x1.22 x 3 m) using three different soil textures (light, heavy, and medium). The emitter outflows were considered 2.4, 4, and 6 lit/hr with irrigation duration of 6 hr. The fertigation treatments included treatments with nitrate concentrations of 125, 250, and 375 mg/L. Urea fertilizer (CH4N2O) (46% nitrogen) was used in the fertigation treatments. Then, using the p theorem of Buckingham and Dimension Analysis (DA), equations were developed to estimate the pattern of nitrate distribution pattern (horizontal and vertical) in the three soil textures. The equations developed were functions of initial soil nitrate content, nitrate concentrations in fertigation, initial moisture, radial distance of points, applied water volume, hydraulic conductivity, and emitter outflows. The results of the comparisons between simulated and observed values showed that the equations were capable of predicting the pattern of moisture distribution in different directions. The averages of Root Mean Square Error (RMSE) values in clay soil and for emitter outflows 2.4, 4, and 6 lit/hr were 0.025, 0.105 and 0.093, respectively. These values for loamy soil were 0.032, 0.052, and 0.05, respectively, and for sandy soil were 0.023, 0.038, and 0.035, respectively. Considering these equations in designing surface drip irrigation systems could improve system performance.
Mina Shakiba; Abdolmajid Liaghat; Farhad Mirzaei
Abstract
Effluent disposal and its harmful impacts on environment are an important challenge in drainage projects and environmental problems in Iran. Therefore, by analyzing the flow net and determining the flow paths, efforts must be made to reduce the amount of effluent and improve its quality. This study aimed ...
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Effluent disposal and its harmful impacts on environment are an important challenge in drainage projects and environmental problems in Iran. Therefore, by analyzing the flow net and determining the flow paths, efforts must be made to reduce the amount of effluent and improve its quality. This study aimed to observe the mixing depth as an effective parameter affecting the salinity of effluent. In this experiment, a plaxiglass model was used to investigate the effect of water table head on mixing depth. Mixing depth is the farthermost flow line below the drainage pipe installation depth. At first, KMnO4 and NaCl were added to groundwater supply to increase the salinity of groundwater to 20 dS/m. Then, by using different input discharge and water table head, the variety of mixing depths was determined with photography. Results showed that with increase in the amount of irrigation water, the water table head and mixing depth increased and caused high salinity of the effluent. For instance, by increasing water table head from 8 cm to 23 cm, salinity of the drainage water raised about 80 percent. Finally, the mixing depth was determined as a function of outflow discharge, hydraulic conductivity, depth of impervious layer, and head in the middle of the drainage water. In the next step, the model was validated using observed experimental field data collected from sugar beet development projects in Amirkabir unit located in Khuzestan, Iran. The comparison was done between the salinity that was simulated by the model and the measured value. The results showed the effect of mixing depth on salinity of effluent.