Modelling of soil cation exchange capacity for some soils of east gharaf lands from mid-Mesopotamian plain (Wasit province/Iraq)

Abstract

This work was carried out in an area located at the mid-Mesopotamian plain, Wasit province/Iraq, and nearly 15 km. south of Kut city and aimed to develop a pedotransfer function to aid in predicting cation exchange capacity value using readily measured soil physicochemical properties. Soil data were subjected to descriptive statistics (minimum, maximum, standard deviation, the coefficient of variation, the coefficient of skewness and kurtosis). Three different combinations of soil physicochemical attributes bulk density (Bd), porosity (p), volumetric moisture content (Pv), texture class (T.C), total available water content (Taw), soil color (col.), clay (C), sand (S), silt (Si), cation exchange capacity (CEC), soil reaction (pH), electrical conductivity (Ec), sodium (Na+), potassium (K+), calcium (Ca+2), magnesium (Mg+2), organic matter (O.M), sodium adsorption ratio (SAR) and exchangeable sodium percentage (Esp) were used in developing models. Consequently, 25 mathematical models were generated. The generated model was cross-validated by means of coefficient of determination (R2), standard estimated error (SEE), root mean squared error (RMSE), mean absolute error (MAE), relative error (RE). In addition, the accuracy and precision of the constructed models were checked by assessing the strength of the relationship between observed and estimated values of cation exchange capacity. The results showed that the model physicochem.1.1 (Y = a * TC + b * Bd + c * T.a.w + d * col. + e * SAR + f * EC + g * Ca+2 + h) was best in predicting the value of soil cation exchange capacity with R2 = 0.98, SEE = 2.243, RMSE = 0.709, MAE = 0.510, RE = 0.016, r = 0.99, S = 0.745.