The evaluation of infiltration characteristics and some parameters of infiltration models such as sorptivity and final steady infiltration rate in soils are important in agriculture. The aim of this study was to evaluate some of the most common models used to estimate final soil infiltration rate. The equality of final infiltration rate with saturated hydraulic conductivity (K s ) was also tested. Moreover, values of the estimated sorptivity from the Philip's model were compared to estimates by selected pedotransfer functions (PTFs). The infiltration experiments used the doublering method on soils with two different land uses in the Taleghan watershed of Tehran province, Iran, from September to October, 2007. The infiltration models of Kostiakov-Lewis, Philip two-term and Horton were fitted to observed infiltration data. Some parameters of the models and the coefficient of determination goodness of fit were estimated using MATLAB software. The results showed that, based on comparing measured and model-estimated infiltration rate using root mean squared error (RMSE), Horton's model gave the best prediction of final infiltration rate in the experimental area. Laboratory measured K s values gave significant differences and higher values than estimated final infiltration rates from the selected models. The estimated final infiltration rate was not equal to laboratory measured K s values in the study area. Moreover, the estimated sorptivity factor by Philip's model was significantly different to those estimated by selected PTFs. It is suggested that the applicability of PTFs is limited to specific, similar conditions. Additional key words: final infiltration rate, saturated hydraulic conductivity, sorptivity. Resumen Evaluación de algunos modelos de infiltración y de algunos parámetros hidráulicosEn la agricultura es importante evaluar las características de la infiltración y de algunos parámetros de los modelos de infiltración, como sortividad y tasa de infiltración constante final de los suelos. El objetivo de este estudio fue evaluar algunos de los modelos utilizados más frecuentemente para estimar la tasa de infiltración final del agua en el suelo, así como estudiar la relación de la tasa de infiltración final con la conductividad hidráulica saturada (K s ) y comparar los valores estimados de la sortividad según el modelo de Philip con los estimados según funciones seleccionadas de edafotransferencia (PTFs). Se realizaron unos experimentos de infiltración en la cuenca de drenaje Taleghan, Teherán, Iran, desde septiembre a octubre de 2007, mediante el método del doble anillo, en suelos con dos diferentes usos. Se ajustaron los modelos de infiltración de Kostiakov-Lewis, el de dos términos de Philip y el de Horton a los datos de infiltración observados. Se estimó la bondad del ajuste de algunos parámetros de los modelos y el coeficiente de determinación mediante el software MATLAB. Al comparar la tasa de infiltración medida y estimada según los modelos, utilizando la raíz del cuadrado medio del error (RMSE)...

Changes in land use can significantly affect soil properties. This study was conducted in the Taleghan watershed of Tehran Province, Iran, to determine the effects of land use changes on soil organic matter (SOM) and soil physical properties including soil aggregate stability, saturated hydraulic conductivity, infiltration rate, available water content, total porosity and bulk density (BD). In the present study, two sites contained adjacent land uses of natural pasture and dryland farming were selected. Soil samples were taken from depths of 0-15 and 15-30 cm for each land use. The results indicated that the conversion of natural pasture to dryland farming led to a significant decrease in SOM at 0-30 cm in the first and second sites (24.7 and 44.2%, respectively). In addition, a significant increase in BD was observed at a depth of 0-30 cm in dryland farm soils (1.39 g cm -3 ) compared to pastureland (1.20 g cm -3 ) at the first site. An increase in BD was also observed at the same depth of dryland farm soils (1.46 g cm -3 ) and pastureland soils (1.42 g cm -3 ) at the second site. In addition, total porosity, mean-weight diameter of aggregates, saturated hydraulic conductivity, available water content and estimated final infiltration rate showed significant differences between land uses. The results showed that the conversion of natural pasture to dryland farming alters soil properties that negatively affect soil productivity and erodibility.

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