University of Mohaghegh Ardabili Water and Soil Management and Modelling 2783-2546 2 3 2022 09 23 Sensitivity analysis of Hydrus software to input data in simulating water movement and root uptake of grass as a reference plant Sensitivity analysis of Hydrus software to input data in simulating water movement and root uptake of grass as a reference plant 94 107 1704 10.22098/mmws.2022.10847.1090 FA Majid Raoof Associate Professor/ Department of Water Engineering, Faculty of Agriculture and Natural Resources, Water Management Research Center, University of Mohaghegh Ardabili, Ardabil, Iran Zeynab Akbari Baseri M.Sc. Graduated Student/ Department of Water Engineering, Faculty of Agriculture and Natural Resources, University Mohaghegh Ardabili, Ardabil, Iran Ali Rasoulzadeh Professor/ Department of Water Engineering, Faculty of Agriculture and Natural Resources, Water Management Research Center, University of Mohaghegh Ardabili, Ardabil, Iran Javanshir Azizi Mobaser Associate Professor/ Department of Water Engineering, Faculty of Agriculture and Natural Resources, Water Management Research Center, University of Mohaghegh Ardabili, Ardabil, Iran 0000-0001-7801-2720 Journal Article 2022 05 28 Introduction Understanding the movement of water in the soil and the process of root water uptake is critical. Numerical simulation is an effective solution for optimizing water management in the field. Accurate prediction of water movement in the soil and root water uptake, to create optimal moisture conditions in the root zone, is important for better plant performance. Investigating the phenomenon of water absorption by roots in hydrological and plant models requires a quantitative description of water absorption by plant roots. Accuracy of model simulation in predicting soil water transfer and root absorption, as temporal and spatial variables, is the most important criterion in agricultural issues. Materials and Methods The water movement in the soil and root water uptake were simultaneously simulated using HYDRUS-3D software. For this purpose, the grass plant was cultivated in three lysimeters with the same soil texture. The grass plant was irrigated every three days at 10 am. The soil water content of the depths of 5, 15, 25, 40, 60, and 80 cm was measured every day at 10 am and 6 pm. The volume of water drained from the lysimeters was measured every day. The measurements were done over a period of 81-day. Soil’s physical properties were measured in the laboratory. Results and Discussion The results showed that in all simulations, the minimum and maximum relative errors were obtained at 0.79 and 35.1%, respectively. The cumulative measured volume of drainage water in the whole period is 162.75 liters and the cumulative volume of simulated drainage water in the whole period is 133.79 liters. The relative error between these two values is equal to 5.28%. Rainfall amounts have a significant effect on estimating the volume of simulated drainage water and its difference from the measured volume of drainage water. With the increase of initial moisture and soil hydraulic conductivity, the relative error between the measured and estimated drainage water data increases, and with the increase of saturated moisture and residual moisture in the soil, the relative error decreases. The values of root water uptake (Minimum 0.5 and maximum 3.5 liters in one irrigation interval), showed that in the third stage of growth, root absorption has the maximum value and by comparing the actual and potential root absorption, which have a low difference, no stress has been applied to the plant. Conclusion The change in the input parameters causes a change in the estimated volume of drained water at the beginning of the period. When the initial moisture and residual soil moisture are considered as 0.3 and 0.15325, respectively, the relative error between the measured and estimated drainage water data is the lowest. The root water uptake values were also estimated using the model. According to the values of actual and potential root water uptake, in the whole period, which has very small differences, no stress has been applied to the grass plant and sufficient water has been provided to the plant. Introduction Understanding the movement of water in the soil and the process of root water uptake is critical. Numerical simulation is an effective solution for optimizing water management in the field. Accurate prediction of water movement in the soil and root water uptake, to create optimal moisture conditions in the root zone, is important for better plant performance. Investigating the phenomenon of water absorption by roots in hydrological and plant models requires a quantitative description of water absorption by plant roots. Accuracy of model simulation in predicting soil water transfer and root absorption, as temporal and spatial variables, is the most important criterion in agricultural issues. Materials and Methods The water movement in the soil and root water uptake were simultaneously simulated using HYDRUS-3D software. For this purpose, the grass plant was cultivated in three lysimeters with the same soil texture. The grass plant was irrigated every three days at 10 am. The soil water content of the depths of 5, 15, 25, 40, 60, and 80 cm was measured every day at 10 am and 6 pm. The volume of water drained from the lysimeters was measured every day. The measurements were done over a period of 81-day. Soil’s physical properties were measured in the laboratory. Results and Discussion The results showed that in all simulations, the minimum and maximum relative errors were obtained at 0.79 and 35.1%, respectively. The cumulative measured volume of drainage water in the whole period is 162.75 liters and the cumulative volume of simulated drainage water in the whole period is 133.79 liters. The relative error between these two values is equal to 5.28%. Rainfall amounts have a significant effect on estimating the volume of simulated drainage water and its difference from the measured volume of drainage water. With the increase of initial moisture and soil hydraulic conductivity, the relative error between the measured and estimated drainage water data increases, and with the increase of saturated moisture and residual moisture in the soil, the relative error decreases. The values of root water uptake (Minimum 0.5 and maximum 3.5 liters in one irrigation interval), showed that in the third stage of growth, root absorption has the maximum value and by comparing the actual and potential root absorption, which have a low difference, no stress has been applied to the plant. Conclusion The change in the input parameters causes a change in the estimated volume of drained water at the beginning of the period. When the initial moisture and residual soil moisture are considered as 0.3 and 0.15325, respectively, the relative error between the measured and estimated drainage water data is the lowest. The root water uptake values were also estimated using the model. According to the values of actual and potential root water uptake, in the whole period, which has very small differences, no stress has been applied to the grass plant and sufficient water has been provided to the plant.

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