Use of pedotransfer function for estimation of hydraulic parameters of silty soils (Argentinean Flatlands)

In this work, different procedures have been used to estimate hydraulic properties of silty soils, representative of a sector of the Argentinean flatlands. It was used grain size, and physical-chemical information of soil maps printed by the National Agriculture Technology Institute (INTA). Characteristic reference values (Rawls et al., 1982; Carsel and Parrish, 1988; Zimmermann 2006a, 2006b), pedotransfer functions (PTF) included in the codes SOILPAR (Acutis and Donatelli, 2003) and Rosetta (Schaap et al., 1999) together with linear regressions among hydraulic parameters and physiques properties (Zimmermann and Basile, 2006, 2007) were used for 321 analyzed samples of soils. Forecasts are compared with values obtained by calibrations of hydrological mathematical models and results of field data of INTA. Results showed that the procedures, which use PTFs had better prediction of hydraulic parameters, mainly the code Rosetta. From a hydrological point of view, it could be simplify the soil profile behavior in two main processes: (a) the retention of moisture which is handled by properties of horizon "A" (silty loam) and (b) the transmission of the vertical flow which is handled by characteristics of horizon "B" (silty clay). In contrast to a good forecast of average values of the hydraulic parameters, a great dispersion among the different used procedures was found. Consequently the methods should be used with caution.