Buffer strip effect on terbuthylazine, desethyl-terbuthylazine and S-metolachlor runoff from maize fields in Northern Italy

The effectiveness of a 6 m-wide vegetative buffer strip for reducing runoff of S-metolachlor, terbuthylazine and desethyl-terbuthylazine was studied in 2007-2008 in Northern Italy. Two cultivated fields, with and without the buffer strip, were compared. Residues of the chemicals were investigated in runoff water collected after runoff events and their dissipation in the soil was studied. The highest concentration of the chemicals in water occurred in samples collected from the unbuffered field at the first runoff events. Losses of terbuthylazine and S-metolachlor in runoff waters were particularly high in 2007 (2.6% and 0.9% of the amount applied, respectively). Soil half-life of terbuthylazine and S-metolachlor ranged between 13.5 and 8.9 days and 16 and 7 days, respectively. Presence of desethyl-terbuthylazine was related to parent compound degradation. The buffer strip allowed important reduction of chemicals content in water (>90%), in particular during the first runoff events.