| چکیده انگلیسی مقاله |
In this study the effect of wastewater treatment applied in alfalfa field management was simulated under HYDRUS-1D in terms of the effects of wastewater treatment on soil nitrate pollution during four growing seasons. The trend of soil nitrate and ammonium concentration was simulated in plant root growth environment employing the HYDRUS-1D model. The Particle Swarm Optimization (PSO) method was employed to determine soil hydraulic and solute transport parameters in the simulation process of the soil ammonium and nitrate changes. Plant yield was 22000 (kg.ha-1) on average per harvest. Also, based on the results of the simulation process can be said that using wastewater treatment has been able to provide nutrients needed by plant during its growth. The results of the simulation process were indicated that the most trend of soil ammonium changes is in the soil surface layer. So that, decreased soil ammonium concentration with increasing soil depth. In contrast, with increasing soil depth, the soil nitrate concentration was increased. Studied solute had oscillating trend in the soil surface layer, even though the trend of soil nitrate changes is less than soil ammonium changes. Fluctuating soil ammonium concentration was related to irrigation water volume, convert soil ammonium to soil nitrate, and soil ammonium adsorption. The trend of soil nitrate and ammonium simulation represented the ability of HYDRUS model to predicate the trend of solute changes under mentioned irrigation method. The obtained results of the statistical indices of RMSE and NSE, from topsoil to the plant root zone showed increasing model accuracy in assessing the trend of soil solute changes. The highest and lowest values of RMSE were 0.01 and 0.004 in model validation process, and 0.008 and 0.001 in model calibration process, respectively. The model accuracy in term of NSE index was obtained 0.94 and 0.98 in the plant root zone in validation and calibration process, respectively. The highest value of soil nitrate in the root zone environment was 0.145 (mg.cm-3 soil). The values of RMSE and NSE indices were obtained 0.0013 and 0.97 in the topsoil, and 0.0009 and 0.87 in the plant root zone respectively. According to the obtained results can be said that HYDRUS model is able to predicate soil ammonium changes based of its input fluctuations and its conversion using optimized soil parameters. Considering the plant yield and the accumulation of nitrate in the soil, it can be said that using unconventional water in compliance with environmental health concerns is a suitable source to supply plant nutrients, improve soil condition in terms of organic matter and provide water required of plant during the growing season in arid and semi-arid regions. |
