Investigation of Empirical Models for Simulation of Soil Wetting Pattern With Drip Irrigation Under Point Source

For drip irrigation systems, to obtain improved water use efficiency, distance between emitters and emitter flow rates must be matched to the soil wetting characteristics, and timing of water to be supplied to the crop. The information on depths and widths of wetted zone of soil plays the great significance in design and management of these systems. The depth and the width of wetted zone is related to soil properties, water application rate, total amount of water in the soil and initial moisture content. In this investigation, an empirical model was developed to simulate dimensions of soil wetted zone under drip source. For this purpose, the field experimental data which was measured in Pardis agricultural farm of Karaj, was used to evaluate semi-empirical model of Zur-Schwartzman and empirical model of Amin-Ekhmaj. The coefficient of these equations determined with both nonlinear regression approach and optimization with least square approach. Predicts of equations obtained from nonlinear regression and optimization approach, predicts of Zur model and predicts of Amin model compared with the observed data. The evaluation of models based on comparison of statistical parameters of simulated data with that observed data. The parameters used were Mean Error (ME), Root Mean Square Error (RMSE) and model efficiency (EF). Very good agreement between theoretical and experimental results improves the validity of these equations. To evaluate above mentioned models also two available published experimental data by Risse et al. (1989) and Li et al. (2004) was used. The results show that suggested equations can be used for wider range of discharge rate and other soil types.