Effect of Hydrus 3D Input Parameters on Simultaneous Simulation of Water Movement and Sugar Beet Root Water Uptake

The accurate prediction of soil water movement and root uptake are very important to provide optimal root zone moisture conditions for increasing plant yield. In this study, soil water movement and sugar beet root uptake were simultaneously simulated, using HYDRUS 3D software, and the effect of extraction methods of input parameters on the accuracy of simulation were evaluated. For this purpose, sugar beet was cultivated in three lysimeters with identical soil texture. Irrigation was performed twice a week (8 on Sunday and 16 on Wednesday). Volumetric water content and drainage water volume from lysimeters were measured before and after each irrigation, respectively. The volume of drainage water from the lysimeters at different times, was selected as objective function. Using measurement, calculation or simulation, the hydrus 3D software input parameters including initial moisture (with two methods), saturated moisture (with three methods), residual moisture (with two methods) and saturated hydraulic conductivity (with two methods), extracted and simulation were completed. The results showed that if the residual moisture derived from measurement (by pressure plate method), saturated moisture derived from RETC software, initial moisture derived from measurement (measured by weighing method) and hydraulic conductivity derived from Rosetta software, were used in the simulation, the simulation accuracy will be highest. The values of relative error, root mean square error, mean absolute error, geometric mean error ratio and coefficient of determination are 17.58%, 0.759 liters, 0.866, 0.777 and 0.885, respectively. Values of GMER parameter, also, showed that in most simulations the model is underestimated.