Hossein Dehghanisanij; Elahe Kanani; samira akhavan
Abstract
Introduction: Partitioning of evapotranspiration (ET) into evaporation from the soil (E) and transpiration through the stomata of plants (T) is important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally, T is the desired component with the water ...
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Introduction: Partitioning of evapotranspiration (ET) into evaporation from the soil (E) and transpiration through the stomata of plants (T) is important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally, T is the desired component with the water being used to enhance plant productivity; whereas, E is considered a source of water loss or inefficiency, and is the basis of the management and organization of water resources. The present investigation was carried out with the objectives evaluation of corn evapotranspiration and its components and relationship between leaf area index and components in surface and subsurface drip irrigation systems.
Materials and Methods: The pilot farm were located in the water and soil department of the ministry of agriculture in Karaj, Iran (latitude of 51°38 ˊN and longitude of 35°21ˊ W, 1312.5 m above sea level). For implementation project was placed 8 volume micro-lysimeters in the soil, which were filled with soil excavated from the study site. The soil inside of micro-lysimeter and the soil of the surrounding study had the same physical-chemical characteristics. The corn was irrigated with surface drip (DI) and subsurface drip irrigation (SDI) system, that was installed just prior to planting in 2014 in a field that was planted to sprinkler-irrigated corn. Daily crop actual evapotranspiration (ETc) of each micro-lysimeter was calculated by applying the water balance method and soil evaporation was measured with micro-lysimeters. Finally, plant transpiration was calculated from difference between the actual evapotranspiration value and amount of evaporation from the soil surface. Leaf area index (LAI), was measured, and it was measured with the electronic leaf area-meter, CI – 202 seven times during the growing season. This method provides an indication of the plant growth.
Results and Discussion: The obtained results indicated that actual corn evapotranspiration was 377 and 371.92 mm for surface drip and subsurface drip irrigation systems, respectively. The value of corn evapotranspiration under surface drip and subsurface drip irrigation increased from initial, to middle season stages. The maximum daily values of ETc occurred on 48 days after planting in middle season stages. The total value of transpiration plant was 5.88, 76.82 and 118.21 mmd-1 for surface drip irrigation system and 12.78, 81.31 and 118.95 mmd-1 for subsurface drip irrigation system in the initial, advance, and middle season stages, respectively. Sum evaporation from the soil surface and crop transpiration was 200.81 and 176.02 mm for surface drip irrigation system and 213.04 and 158.81 mm for subsurface drip irrigation system. So, amount of evaporation from the soil surface was 73.02, 65.73 and 37.32 mm for surface drip irrigation system and 65, 58.83 and 34.98 mm for subsurface drip irrigation system in the initial, advance, and middle season stages, respectively. In surface drip and subsurface drip irrigation was allocated approximately 93 and 83 percent of evapotranspiration to evaporation from the soil surface respectively. The minimum daily values of E/ETc were 37 and 34 mm for surface drip and subsurface drip irrigation systems respectively, and occurred in middle season stages. Amount of transpiration was 5.88, 76.82 and 118.21 mm for surface drip irrigation system 12.78, 81.31 and 118.95 mm for subsurface drip irrigation for the initial, advance and middle season stages, respectively. The relationship between T/ETc and LAI was fitted to a polynomial equation with significant correlation coefficients, R2 = 0.95 and 0.89 for surface drip and subsurface drip irrigation systems, respectively. T/ETc started from 0 at sowing, and reached to its maximum at the middle growth stage or when LAI reached to about 3.0. Also, the relationship between E/ETc and LAI was fitted to a polynomial equation with significant correlation coefficients, R2 = 0.97 and 0.88 for surface drip and subsurface drip irrigation systems respectively, and reached to its minimum at the middle growth stage. Also the results showed that subsurface drip irrigation systems have higher biological yield and higher values for plant parameters in compared to surface drip irrigation system that it shows subsurface drip irrigation system due to evaporation reduction, better weed control and direct transport of water to the developmental zone has a significant role in increasing corn yield.
Conclusion: The results of this study indicated that soil evaporation losses in subsurface drip irrigation system had lower than surface drip irrigation system. Also, had higher transpiration in the growth season. This could perform important role on yield of crop. These results should help the precise planning and efficient management of irrigation for these crops in this region.
samira akhavan; A. Mahdavi
Abstract
Introduction: Surface irrigation is still the most used method. For accessing to high efficiency, irrigation requires careful design and correct implementation. In addition, the design and evaluation of these systems require the identification of the advance, recession, and infiltration curves. Infiltration ...
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Introduction: Surface irrigation is still the most used method. For accessing to high efficiency, irrigation requires careful design and correct implementation. In addition, the design and evaluation of these systems require the identification of the advance, recession, and infiltration curves. Infiltration is the most important and difficult parameter to evaluate surface irrigation systems. The objective of this study was to evaluate five different methods to estimate infiltration parameters (two-point method of Elliott and Walker, recycling furrow infiltrometer, Singh and Yu method, Shepard one-point method and modified Shepard et al. two-point method) and to determine the most compatible method with design and evaluation models of furrow irrigation (hydrodynamic, kinematic wave and zero inertia) by applying SIRMOD software.
Materials and Methods: For the simulation of the surface irrigation, the continuity and momentum equations (Sant-Venant equations) used. SIRMOD simulation model is one of the models for the management and design of surface irrigation systems. The software package, hydraulic hydrodynamic models, zero inertia and kinetic wave have been placed. These models are resolvent of the Sant-Venant equations based on various assumptions. In this study, two-point method of Elliott and Walker, recycling furrow infiltrometer, Singh and Yu method (to calculate the coefficients of Kostiakov-Louis equation), Shepard one-point method and modified Shepard et al. two-point method (to calculate the coefficients of Philip equation), were used for estimating infiltration parameters. For this purpose, three field data sets were used. The total infiltrated water volume and advance time were predicted in each infiltration method and irrigation simulation model. In order to compare and evaluate the mentioned methods, the relative and standard errors were calculated.
Results and Discussion: According to the five methods (two-point method of Elliott and Walker, recycling furrow infiltrometer, Singh and Yu method, Shepard one-point method and modified Shepard et al. two-point method) Kostyakof- Louis and Philippe equations coefficients were determined. To evaluate the different methods for estimating infiltration parameters, the volume of water penetration in the furrow length was estimated using five named methods and the findings were compared with the actual volume of infiltrated water in the furrows (was estimated using the input-output hydrograph). Values of relative error in estimating the infiltrated volume in the furrows show the two-point Elliott and Walker method with 9.2 percent relative error is the lowest error than other methods. Then recycling furrow infiltrometer (back water) method is with 21.4 percent relative error. The standard error in the simulation and predict the advance stage in furrows based on different estimated parameters showed that hydrodynamic model by two-point Elliott and Walker method will give the best results (with 12.86 percent standard error). Also in Kinetic Wave model, recycling furrow infiltrometer method has the lowest standard error (10.04 percent) and zero inertia models with two-point Elliott and Walker method have lowest standard error (12.81 percent). In Hydrodynamic and zero inertia models, recycling furrow infiltrometer and two-point method of Elliott and Walker and Singh and Yu method have estimated advance figures in furrow less than its actual value. Shepard et al. one-point method underestimated about 100 meters of furrow length and overestimated from this point to the end of the furrow. Modified Shepard et al. two-point method is generally overestimated. In the kinetic wave model, two-point Elliott and Walker and recycling furrow infiltrometer methods numbers have been estimated to be completed in accordance with the numbers seen in a distance of about 40 meters along the furrow and the low estimate since the end of the furrow. Singh and Yu method overestimated. Shepard et al. one-point and Modified Shepard et al. two-point method were like the other two models.
Conclusions: Elliott and Walker two-point method is generally the least error in the calculation of the total volume of infiltrated water through the grooves, compared to other methods and then using rotating penetrometer (back water) is located. In general it can be said that both recycling furrow infiltrometer and two- point Elliott and Walker, the most appropriate methods to determine the infiltration equation parameters than other methods under study and using them in all three hydrodynamic, kinematic wave and zero inertia models, the results of the simulation irrigation, have created the smallest error. In general, the kinetic wave model than hydrodynamic and zero inertia models, was estimated more accurately the data in water advance stage and this trend can be seen in every five methods for estimating the infiltrated parameters. However, calculated errors in both hydrodynamic and zero inertia models in predicting this stage of irrigation are almost equal.
