Masoud Soltani; Ali Rahimikhoob; abbas sotoodeh nia; mojtaba akram
Abstract
There is threat of salinizing for irrigated area in arid and semi-arid areas. Agriculture sustainability under this condition is dependent on removal of excess salt from the root zone. Although conventional drainage systems could provide suitable condition for root zone growth by removing excess water ...
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There is threat of salinizing for irrigated area in arid and semi-arid areas. Agriculture sustainability under this condition is dependent on removal of excess salt from the root zone. Although conventional drainage systems could provide suitable condition for root zone growth by removing excess water and salt, these systems face some challenges such as high initial capital, environmental problems, high volume and low quality of drained water at outlet. Alternative systems or their combination with conventional ones may be good solution for these problems. In this study, dry drainage (DD) was conducted as environmental and economical alternative technique. This research was carried out to evaluate DD and calibrate HYDRUS-2D model, in July, 2015, at Aburaihan Faculty, University of Tehran. Necessary data was collected from lysimeters in research field of irrigation and drainage Eng. Department to calibrate the model and investigate DD. Treatments were carried out in four lysimeters with dimension of 1×1×1 m and included two ratios of cultivated to uncultivated width strip (1(cultivated):1(uncultivated); and 2:1) and two levels of irrigation water salinity (1.5 and 3 dS m-1). Shallow water table was at 90 cm and study was continued for 70 days. Results showed that salt moving direction was from the irrigated to the bare evaporation strips at all treatments, and final soil salinity of uncultivated was much more than the cultivated area. Also, increasing cultivated to uncultivated width (from 1:1 to 2:1) could transport soil salinity from the irrigated to evaporation strip, but it couldn’t stabilize salinity of the root zone. Final salinity of root zone in treatments with ratio of 1:1 was not more than 6 dS m-1 (1.7 to 2.7 times of initial soil salinity).Thus, for the other two treatments, the final salinity was more than 14 dS/m (4.9 to 7.7 times the initial soil salinity). Results of modeling and statistical indexes showed that HYDRUS_2D could simulate water flow and salinity transport well in lysimetric DD. SE and NRMSE for simulated soil moisture were between 7% to 11 percent and 0.021 to 0.057 cm3 cm-3,respectively, and these values for simulated soil salinity were between 24% to 29 percent and 2.01 to 2.73 dS m-1, respectively. Based on statistical indicators, HYDRUS_2D simulated soil moisture better than soil salinity.
Habib Karimi Avargani; Ali Rahimikhoob; Mohammad Hadi Nazarifar
Abstract
Crop Simulation models are used for water management in farms and are widely used for optimization of water use efficiency. AquaCrop model, developed by FAO, is based on yield response to water. Compared to other similar models, AquaCrop requires fewer input parameters. The objective of this study was ...
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Crop Simulation models are used for water management in farms and are widely used for optimization of water use efficiency. AquaCrop model, developed by FAO, is based on yield response to water. Compared to other similar models, AquaCrop requires fewer input parameters. The objective of this study was evaluation of this model for barley under deficit irrigation in Pakdasht region. The experiment was done in 2014-15 growing season and included three irrigation treatments and three sowing dates. The irrigation treatments included full irrigation and two treatments of 80% and 60 percent of full irrigation. Sowing dates included early, normal, and late planting. Comparing the estimated values of AquaCrop model and measured values showed that the model is well capable of simulating the barley biomass production. Average R2, RMSE and MBE for the comparison between measured and estimated values were calculated to be 0.96, 8.4 %, and 2.6 %, respectively.
Arash Ranjbar; Ali Rahimikhoob; H E; Maryam Varavipour
Abstract
Transport and transformation of urea, nitrate, and ammonium in the soil take place as a sequential decay chain reactions which should be considered altogether for more precise management of water and fertilizer in agricultural farms. In this study, HYDRUS-2D model was evaluated to predict distribution ...
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Transport and transformation of urea, nitrate, and ammonium in the soil take place as a sequential decay chain reactions which should be considered altogether for more precise management of water and fertilizer in agricultural farms. In this study, HYDRUS-2D model was evaluated to predict distribution of water, nitrate and ammonium under furrow and ridge during the growing period of maize. Thus, maize was planted in the treatments with nitrogen rates of 0, 150, and 250 kg ha-1. The amounts of nitrogen uptake, soil water, nitrate, and ammonium concentrations during the growing season, before and after fertilization, and after harvesting were measured over different depths under ridges and furrows. Results showed suitable agreement between predicted and measured water, nitrate and ammonium distribution in soil during validation stage. NRMSE and R2 as evaluation indexes for the predicted soil water were calculated as 0.772 and 4.37%, respectively. Besides, these indexes were calculated for the predicted ammonium concentration under furrow and ridge for all treatments and were found to be in the range of 0.645-0.798 and 14.23%-29.4%, and for the predicted nitrate concentration, they were in the range of 0.716- 0.829 and 23.57%- 25.2%, respectively. According to the results of this study, the HYDRUS model is a useful tool for management of water and fertilizer in furrow irrigation.
m y; j s; Mohammad Ebrahim Banihabib; a r; a r; e s
Abstract
Due to extensive agricultural activities on the plains and the use of chemical fertilizers containing nitrogen, significant amount of this element enter the aquifer. On the other hand, effluent of wastewater treatment plants is used in irrigation and drainage networks as an alternative or supplementary ...
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Due to extensive agricultural activities on the plains and the use of chemical fertilizers containing nitrogen, significant amount of this element enter the aquifer. On the other hand, effluent of wastewater treatment plants is used in irrigation and drainage networks as an alternative or supplementary source of surface water. Therefore, adoption of strategies for reducing and controlling the amount of nitrogen that enters the soil and aquifer is an important issue. The aim of this research was to develop a cropping pattern optimization model by quantitative-qualitative conjunctive use of unconventional surface water (wastewater) and groundwater. The three objectives of the model were maximizing profits from cropping pattern, reducing nitrogen leaching, and improving the rate of aquifer recharge. In order to integrate management of wastewater and irrigation water resources, the nonlinear three-objective optimization model was run for 7 scenarios (one-objective, two-objectives, and three-objectives) in water year 2012-2013, for Varamin irrigation network. The input data required for the model were collected in two ways: regional testing and obtaining information from various institutions.Solving one-objective model by first objective (first scenario: improving the network’s profit) showed the 49 percent improvement in the network’s net profit. The second objective (second scenario: reducing of fertilizer consumption) showed 95% reduction of fertilizer consumption, and the third objective (third scenario: improving the aquifer recharge) showed 120% improvement in the aquifer recharge, in comparison to the current situation. Solving the three-objective model (seventh scenario: combined objectives of improving network’s net profit, reducing fertilizer consumption, and improving the aquifer recharge) showed a reduction of 23% in cultivated area, 71% in nitrogen fertilizer consumption, and 13% in conjunctive withdrawals of wastewater and groundwater. Also, these reductions increase net benefit by 6%, aquifer recharge by 29%, and water productivity by 22%. Therefore, the seventh scenario was chosen as the best scenario. The results of this research could be adopted for optimum use of water resources, increasing farmers’ benefit, and decreasing nitrogen leaching in irrigation network projects. However, it is to be noted that, generally, use of wastewater for irrigation of food crops is not recommended.