Abstract

Soil water retention curve is necessary for many studies of water and solute transport in soils. Among the developed mathematical models, one of the most widely used models to describe the water-retention curve of soils is van Genuchten model. Its four parameters are the key to application of this model. In this study we introduced in detail the parameter estimation procedure of the model using DPS system based on the retention data (namely soil water suctions and corresponding soil water contents for cinnamon soil in northeastern China), and obtained the values of the four parameters. The water content values calculated by established model and the measured values were analyzed with the methods of variance analysis and residual analysis. The results showed that the nonlinear regression model had good estimate effects, and the relationship between estimated and observed values was significant at to 0.0001 levels. Additionally, the root mean square residual (RMSR) between measured and estimated water contents was less than 0.008 cm³ cm^-3and the absolute values of relative error of soil water contents was in the range of 0.05 to 7.0%. Although the estimated parameter values of van Genuchten model using DPS had the same precision as those estimated with MATLAB, the efficiency and universality was improved obviously as compared to those using MATLAB. Therefore, this method is practical and feasible to obtain values of four parameters of van Genuchten model for soil scientists.

Key words: Soil water retention curve, van Genuchten model, degree of phosphorus saturation (DPS) system.