Losses of atrazine, metolachlor, prosulfuron and triasulfuron in subsurface drain water. I. Field results

The objective of this experiment was to estimate field-scale losses of metolachlor, prosulfuron, triasulfuron, atrazine and two of its metabolites (deethylatrazine and deisopropylatrazine) in subsurface drain water of two experimental sites located in the Po Valley (Italy), from April 1996 to March 1999. Atrazine and metolachlor concentrations in drain water of the two experimental sites showed similar patterns. However, different concentrations were observed. In the Cadriano silty loam, concentration peaks of 20.6 and 18.2 μg·L-1, respectively, for atrazine and metolachlor, were observed. In the Carpi silty clay, higher concentrations were observed (atrazine: 127.0 μg·L-1, metolachlor: 180.0 μg·L-1). The results obtained suggest an involvement of preferential flow in the overall transport of the four herbicides in the soil. Estimated losses of atrazine, metolachlor, prosulfuron and triasulfuron in subsurface drain water were respectively 0.27, 0.61, 2.3 and 0.73% of the applied rate in Cadriano, and 2.14, 1.14, 10.6 and 0.07% of the applied rate in Carpi.