Fig. 4. Root mean squared residuals (RMSRs) for several matric potential values for the direct fitting of the van Genuchten equation and using four selected models (M2, M3, M5, M9) and each of the data sets used to develop pedotransfer functions. HUN, Hungarian data set; EUR, European data set; ICO, intercontinental data set. Input parameters of the four models are listed in Table 2.