DEVELOPMENT AND EVALUATION OF PEDOTRANSFER FUNCTIONS FOR ESTIMATING CATION EXCHANGE CAPACITY OF SOILS IN KADUNA STATE, NIGERIA

Investigation of soil properties like Cation Exchange Capacity (CEC) plays important roles in agricultural production and environmental researches, which led to development of indirect methods in estimation of this soil characteristic. Laboratory procedures for estimating CEC are cumbersome, expensive, and time-consuming, it is essential to develop an indirect approach such as Pedotransfer functions (PTFs) for the prediction of this parameter from more readily available soil data. The aim of this study was to develop various PTFs models for estimating CEC in soils, and to select the best models to be used in the study area. Sixteen profiles were sunk in the Kaduna State, and eight from each zone (Northern and Southern Guinea Savannah). The profiles data were categorized into three groups as; Northern Guinea Savannah (NGS-Model), Southern Guinea Savannah (SGS-Model), and Kaduna General (KG-model). In each of the category, the data were divided into two sets for PTFs development and evaluation. Multivariate regression analysis was used to develop the models. Two CEC models were developed from each of the three categories. Four statistical evaluation parameters (Mean Error, Root Mean Square Error, Coefficient of Determination, and Index of Agreement) were used to test the performance of generated models on validation data set. The results showed SGS-CEC2 model was the best (ME = -0.39, RMSE = 2.28, d-index = 0.99) for estimating CEC when tested on soils of the other zone, followed by SGS-CEC1 model (ME = -1.18, RMSE = 3.32, d-index = 0.99), and then KG-CEC2 (ME = -2.69, RMSE = 8.06, d-index = 0.99).The study revealed that, the developed PTFs models will served as an alternative method for estimating CEC in soils, which might reduce cost, labor and time. Furthermore, this study has brought out clearly relevant soil information that can guide decision related to the use and management of soils on sustainable basis. It is recommended that developed PTFs should be tested in many soils before used, and many PTFs models should be developed for other soil properties. Keywords: Cation Exchange Capacity, Pedotransfer Functions (PTFs), NGS-Model, SGS-Model, KG-model