Irrigation
M. Khorramian; M.S. Hasanvandi; S.R. Ashrafeizadeh
Abstract
Introduction: North of Khuzestan province is one of the major areas for autumn sugar beet planting. Conventional tillage (CT) is widely practiced by sugar beet growers in this region. CT in sugar beet consists of burning wheat residue, using deep plowing with a moldboard plow or ripper plowing followed ...
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Introduction: North of Khuzestan province is one of the major areas for autumn sugar beet planting. Conventional tillage (CT) is widely practiced by sugar beet growers in this region. CT in sugar beet consists of burning wheat residue, using deep plowing with a moldboard plow or ripper plowing followed by several passes of disking, leveling, and furrowing. These aggressive tillage practices have many negative consequences for soils. Losses of soil organic carbon decreases soil permeability and consequently increases soil erosion and surface runoff. Therefore, applying conservation agriculture principles in sugar beet planting, conservation of residues and elimination or reduction of tillage, can help to optimize water use management and improve soil health on a farm scale. The objectives of this study were (i) to determine the possibility of direct planting of autumn sugar beet in wheat residues, (ii) to estimate sugar beet yield and crop water productivity (WP) under CT, chisel (CH), minimum tillage (MT) and no-tillage (NT) systems, (iii) to evaluate the response of sugar beet cultivars (Sharif and Palma) to different soil tillage systems, and (iv) to determine the effect of soil tillage systems on some soil physical properties.Materials and Methods: A field experiment was conducted for two years (2016—2017) at the Safiabad Dezful Agricultural Research Center (32° 14.44´-32°15.93´ and 48° 25.41´-48°47). The soil of the study site was deep, well-drained with a silty clay loam texture. The mean annual precipitation and evaporation are 317 and 2400 mm, respectively, with an elevation of 108 m above mean sea level. Irrigation water was supplied from the Dez irrigation network without any salinity restrictions. The experimental was conducted in a split-plot arrangement based on a randomized complete block design with three replicates. The main-plot treatment was tillage method and the subplot treatment was two sugar beet cultivars (Palma and Sharif). Tillage treatments included conventional tillage (CT) (moldboard ploughing + MT steps), chisel (CH) (chisel ploughing + MT steps), minimum tillage (MT) (two perpendicular disks, fertilizing centrifugal machine, disking, furrowing, planting with pneumatic row planter), and no-tillage (NT) (spraying, planting with NT pneumatic row planter). The length and width of each plot were 100 and 6 m, respectively, and row spacing was 75 cm.Soil penetration resistance or cone index (CI) readings were recorded in 2 cm increments to a depth of 50 cm using SP1000 digital penetration tester to reflect the soil compaction. Soil bulk density was determined in 0-10 and 10-20 cm layers. In the first and second year, sugar beet samplings were done 216 and 220 days after planting, by harvesting a row of 75 cm with length of 10 m (7.5 m2). WP was calculated by dividing the root and sugar yield to irrigation water and effective rainfall (effective rainfall was calculated every year with SCS method). Composite data analysis and mean comparison were performed with MSTATC statistical software.Results and Discussion: Results of CI showed no significant difference between four tillage methods at 0-10 cm depth. With increasing depth up to 30 cm, slight differences in soil compaction were observed for different tillage treatments, especially in the second year. Overall, compaction in the 0-50 cm profile in the CT and CH method were about 45% and 33%, respectively, lower than NT method, whereas in MT method it was about 37% higher than NT method. Results of root branch number analysis showed that the NT and CT treatments had the lowest branching (2.67 and 2.83, respectively) and the two CH and MT treatments had the highest branching (4.2 and 5.3, respectively). Therefore, NT had no negative effect on root growth of sugar beet. The results of bulk density measurements in the 0-10 cm layer were consistent with the results of the CI, but at depth of 10-20 cm, NT method with the highest bulk density (1.71 g cm-3) had significant difference with the other three tillage methods. Tillage method had no significant effect on root and sugar yield and root and sugar WP. However, in CT treatment, root yield increased by 6-8.5% and sugar yield by 6-12%, while root and sugar WP in NT treatment was about 8% higher than in the other three tillage treatments. On the other hand, changing climate conditions, especially rainfall during two years of the experiment, resulted in significant interaction between year and cultivar for yield and WP at 1% probability level. In the first year, the yield of Sharif cultivar (86.7 t ha-1) was higher than Palma (80.2 t ha-1), but in the second year, despite the decreasing yield of both cultivars, higher resistance of Palma cultivar to Cercospora disease resulted in a significant increase in sugar yield and WP over last year.Conclusion: The two-year results of this study showed that the direct planting of autumn sugar beet in wheat residues (NT) is possible. Sugar beet yield and WP were not significantly different in tillage methods, but NT reduced tillage traffic from 7 times to 2 times and reduced energy consumption. The response of the two sugar beet cultivars to different tillage methods was the same and among them the Palma cultivar had the highest yield because of its higher resistance to Cercospora disease.
Mohammad Reza Emdad; arash tafteh; saeed ghalebi
Abstract
Introduction: Simulation models have been used for decades to analyse crop responses to environmental stresses. AquaCrop is a crop water productivity model developed by the Land and Water Division of FAO. It simulates yield response to water of herbaceous crops, and is particularly suited to address ...
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Introduction: Simulation models have been used for decades to analyse crop responses to environmental stresses. AquaCrop is a crop water productivity model developed by the Land and Water Division of FAO. It simulates yield response to water of herbaceous crops, and is particularly suited to address conditions where water is a key limiting factor in crop production. It is designed to balance simplicity, accuracy and robustness, and is particularly suited to address conditions where water is a key limiting factor in crop production. AquaCrop is a companion tool for a wide range of users and applications including yield prediction. Aquacrop has high accuracy and performance for yield prediction than other models regarding to irrigation and fertilizer management base foundation. Using Aquacrop model for crop yield simulation in different soil and water managements has high accuracy and its use requires calibration and validation. The use of models saves time and cost and, if calibrated and validated, acceptable results are expected.
Material and Methods: This research was carried out in order to calibrate and validate the Aquacrop model for simulating wheat grain yield in the three selected pilots in Hamidiyeh province of Khuzestan province in two years of cultivation.In this regard, three different plots with a total area of about 10 hectares were selected in Hamidyeh region. Sampling, measuring and determining the parameters of soil, water, plant, irrigation management (information required for the Aquacrop model) and the existing conditions of the area were carried out.The climatic data required in Aquacrop model was collected from synoptic meteorological weather station of Ahvaz. Irrigation water quality with mean water salinity of 1.9 dS/m has a good quality for irrigation. In the first year, 5 irrigation events (with a total volume of 9500 cubic meters per hectare) are available to the wheat plant at different stages. In this regard, based on meteorological data and field and vegetation data that was taken from the field level in the first year, the Aquacrop model calibration and performance variations were carried out at different times of irrigation using a simulation model. In order to validate the results simulated by the model, the best scenario provided by the model in the second year was implemented at selected farm level and its results were compared with the simulation results by the model.
Results and Discussion: Aquacrop model calibrated for the first year and then compared for different scenarios of irrigation timing (3-6 irrigation event).The amount of grain yield and total in 4 irrigation intervals are not different with the corresponding values in 5 irrigation intervals. Irrigation rotations were considered in accordance with routine irrigation rotations of the region during planting, tillering, stemming, flowering and seed filling (5 turns) for 4 steps of irrigation step and for 3 irrigation stages, the tiller and stem elongation was deleted. The model showed that, using four irrigation timing is the most appropriate irrigation scenario. Using the results of the model with considering 4 irrigation times, wheat was planted in the second year for model validation. In the second year, the average of measured and simulated wheat grain yield was 3.8 and 4.4 t/h (with 14% error).Average values of total yield and simulated wheat seeds in 4 and 5 irrigation intervals were not different, while the amount of water consumed in 4 irrigation intervals decreased by 20% compared to 5 irrigation intervals. On the other hand, water use efficiency increased by up to 21% in 4 irrigation intervals compared to 5 irrigation intervals. Also, according to the simulation, it was observed that increasing the irrigation interval at the arrival stage, while not significantly increasing the grain yield and the total, did not increase the water use efficiency in order to increase the water consumption (one irrigation interval) Reduced. Considering 3 irrigation timing, the grain yield decreased by 15%. Due to the reduced yield in three irrigation intervals than the more irrigation intervals, this scenario is not recommended for performance reasons. So, according to the simulation, at least 4 irrigation intervals (during planting, stemming, flowering and seed filling) are recommended to maintain proper production level in existing conditions. Comparison of statistical indices between measured and simulation values of wheat grain yield in both years showed that the coefficient of correlation, normalized root mean square error (RMSE) and agreement index were 0.9, 0.14, and 0.89 respectively, which indicates the proper performance of the model for simulating yield of wheat for two consecutive years. The average grain yield of simulated wheat has been estimated at 3.8 ton / ha, which estimates 14% of grain yield less than actual experimental conditions compared to its measured value, indicating the accuracy and efficiency of this model in simulating wheat yield in the present situation. With considering 4 irrigation events, the water use efficiency of wheat grain yield increased by 0.7 kg/m3, which confirms the ability and accuracy of the Aquacrop model for simulating grain yield of wheat and also improving water use efficiency.
Conclusions: The results of this study showed that the simulation of wheat yield in the first year (2.6 t/ha) has a close proximity to the measured values of yield (3 t/ha). Also, validation of the model with changing conditions in the second year showed that the simulated yield of wheat (4.4 t/ha) also had a good agreement with its measured value (3.8 t/ha), which indicates the high accuracy of this model in simulating wheat grain yields every two years. Therefore, this model has the efficiency and accuracy in simulating wheat yield in research conditions.
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.
