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Desarrollo de funciones de edafo-transferencia para la caracterización hidráulica de andosoles

Abstract:

The hydraulic characterization of the soil, that is required for modelling studys, implies a lot of work and high costs. Indirect methods to estimate the water retention curve and the hydraulic conductivity have gained recognition. Among these methods we have the Pedo-Transfer Functions that are obtained from the relationships that exist between soil hydraulic properties, with other basic properties (texture, bulk density, organic matter, etc.). The present work was carried out with the purpose of develop equations that allow to estimate the CRHS and the Ks from soil properties easy to obtain for Andosols. Pedo-Transfer Functions were obtained to estimate 6 independent points of the soil water retention curve, to estimate the Ks and the 4 parameters of the van Genuchten model for the Andosols of Ecuador. The database that was used consists of 87 samples for the development of FET and 13 for its validation. For the development of FET, multiple linear regression models (MRLM) and artificial neural networks models (MRNA) were used. It was determined that for estimate individual points of the CRHS both methods are similar in effectiveness. On the other hand it was found that the MRLM and the MRNA would not be adequate to develop FET that estimate the parameters of the van Genuchten model for Andosols. In general with the FET developed based on MRLM for points of the CRHS, good results were obtained (R2 values higher than 0.6) and estimated the CRHS better than the FET of Rawls et al. (1982), when they were compared using the validation data set. In the estimation of Ks the FET based on MRLM presented R2 values ranged from 0.5 to 0.7. Additionally they were compared with the FET of Rosetta (Schaap et al., 2001) and RETC (van Genuchten et al., 1991) programs. This comparison revealed a better performance, of FET developed in this study, in the estimate of the CRHS. Finally, measurements were made to compare the Ks in samples taken in vertical direction and in horizontal direction, in an area of the Ecuadorian Austro páramo. It was found that isotrophy conditions would exist for the Andosols where the experiment was made. This would simplify some aspects of the study of soil water movement.