Developing Pedotransfer Functions for Estimating Field Capacity and Permanent Wilting Point Using Fuzzy Table Look-up Scheme

Abstract

Study of soil properties like field capacity (F.C) and permanent wilting point (P.W.P) plays important roles in study of soil moisture retention curve. Pedotransfer functions (PTFs) provide an alternative by estimating soil parameters from more readily available soil data. In this study, a new approach is proposed as a modification to a standard fuzzy modeling method based on the table look-up scheme. 70 soil samples were collected from different horizons of 15 soil profiles located in the Ziaran region, Qazvin province, Iran. Then, fuzzy table look-up scheme was employed to develop pedotransfer functions for predicting F.C and P.W.P using easily measurable characteristics of clay, silt, O.C, S.P, B.D and CaCO₃. In order to evaluate the models, root mean square error (RMSE) and R² were used. The value of RMSE and R² derived by fuzzy table look-up scheme for F.C and P.W.P were (1.65, 0.87) and (1.03, 0.83), respectively.