Losses of atrazine, metolachlor, prosulfuron and triasulfuron in subsurface drain water. II. Simulation results

The MACRO model was applied to predicting the losses of atrazine, metolachlor and prosulfuron in subsurface drain water of two experimental fields located in the Po Valley, Cadriano and Carpi (Italy). For the entire simulation period (March 1996 to February 1997) MACRO was able to predict the drain flow of the two experimental sites (111 and 93% of the total measured drainage drain water, respectively, in Cadriano and Carpi). Atrazine and metolachlor losses via the drain were predicted at 46.8% to 29.9% in Cadriano and 45.3% to 20.9% in Carpi, respectively. The losses of prosulfuron were overestimated (200%) in Cadriano whereas they were underestimated (66.7%) in Carpi. The model simulated most of the drainage events but it failed at simulating the concentration of atrazine and metolachlor in the first drainage events after the herbicide application when the highest concentration of the study was observed. Mass losses in each event were clearly a function of the soil and herbicide properties and the model followed this trend well.