Evaluation of LEACHM model for predicting atrazine movement in two Kansas soils

Atrazine concentration data obtained from a monolith weighing lysimeter experiment was used to calibrate and validate the pesticide version of Leaching Estimation And Chemistry Model (LEACHM). As one of the lysimeter soil was predominantly clay with wide cracks on the surface, the macropore flow component of Root Zone Water Quality model was added to LEACHM in order to better represent the lysimeter conditions. An statistical analyses of predicted and measured data showed that the performance of LEACHM without the macropore flow component was better. But, from the plots of measured versus predicted atrazine concentrations, it was found that the addition of macropore flow component did improve the simulation capability of LEACHM but it caused the model to overpredict the concentrations most of the time. Therefore, although there was a qualitative improvement in predictions, LEACHM needs considerable modifications to represent the physical processes within the lysimeter system.