Comparing and evaluating pesticide leaching models: results for the Tor Mancina data set (Italy)

This paper describes the results of an evaluation of pesticide leaching mod elling, using data collected on four lysimeters in Italy. The experimental data were collected during a 3 year period at Tor Mancina (Rome, Italy), on a clay-loam calcareous soil. Monitored variables are the soil water draina ge, the bromide leaching and the metolachlor leaching. Two different irriga tion schedules were considered in the experimental design. The models inade quately described the monitored breakthrough of water, bromide and pesticid e. Poor modelling performance was firstly attributed to an inappropriate mo del structure, poorly representing the specific conditions of Mediterranean soils. In particular, the models did not allow to represent correctly the preferential flow that was observed during some of the flow events. Secondl y, deficiencies were identified in the calibration procedures, and the appl ication of a well defined modelling practice, The lack of such a good model ling practice induced user subjectivity in the estimation of the model para meters, which had an impact on the modelling results. (C) 2000 Elsevier Sci ence B.V. All rights reserved.