PERFORMANCE EVALUATION OF CHEMFLO MODEL IN SIMULATING FERTILIZER SOLUTE TRANSPORT THROUGH LATERITIC SOILS

摘要

Predicting contaminants in the vadose zone is a challenging task because of the complex nature of underlying flow fields. The present study was carried out to investigate NO_3~- and K~+ transport through the lateritic soil profile and to assess the efficacy of the CHEMFLO transport model in simulating the transport process in the lateritic soil. An experimental plot was developed for the present study and KNO_3 was applied in slug form, which was displaced by maintaining a constant depth of water forabout 4.5 days, Leachates from different depths, and the water samples from nine vadose zone observation wells were collected at regular intervals for chemical analysis. The results revealed that NO_3~- and K~+, concentrations in the soil-water in all the layers up to a depth of 148 cm were maximum just one day after the start of slug displacement. Moreover, the CHEMFLO model was calibrated and used to simulate the temporal variation of NO_3~- and K~+ concentrations at different soil depths. The simulated NO_3~-and K~+ concentrations were compared with the observed ones. The results of the simulation analysis indicate that the CHEMFLO model could not simulate the peak concentration satisfactorily at any depths. The performance of the model was evaluated based on statistical indicators, viz., mean error (ME), relative error (RE), root mean square error (RMSE), coefficient of variation (C_v) and model efficiency (EF). These goodness-of-fit statistics for NO_3~-and K~+ concentrations suggest that the current version of the CHEMFLO model could not reasonably simulate water and solute transport through the lateritic soil under study, The shortcomings of the model are highlighted and the need for evaluating some better transport models is emphasized.