Evaluation of a simulation model for predicting soil-water characteristics of selected agricultural fields

Abstract

The ability of the Soil Water Characteristics-Hydraulic Properties Calculator (SWC-HPC) model in predicting soil-water characteristics of agricultural fields in Zaria, Nigeria, was tested and reported in this study. The goal was to establish the predictability and reliability of the model, and hence, its use in determining water characteristics of soils in the study area. Fortty soil samples collected from four irrigation sites were used in the evaluation. The soils particle size distribution (specifically, percent clay and sand) and organic matter contents were inputted into the model to simulate soil moisture status at saturation, field capacity and wilting point, soil bulk density and saturated hydraulic conductivity. The model outputs were statistically compared with observed parameters from laboratory tests using root mean square error (RMSE), coefficient of variation (CV), modeling efficiency (BF) and coefficient of residual mass (CRM). The model accurately simulated the observed bulk densities of the soil tested, satisfactorily simulated soil moisture content at field capacity, and moderately simulated moisture content at saturation and wilting point. The model however, poorly simulated saturated hydraulic conductivity of the soils tested. The SWC-HPC may therefore be used only to simulate soil bulk densities and moisture status at saturation, field capacity and wilting point inthe study locations.