Herbicide losses in runoff events from a field with a low slope: Role of a vegetative filter strip [An article from: Chemosphere]
Description
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Description:
Herbicide runoff and the effects of a narrow vegetative filter strip (VFS) were studied on an arable field in the low-lying plains of the Veneto Region (north-east Italy). Cultivated plots were compared with and without a 6m wide VFS composed of trees, shrubs and grass. Natural and simulated runoff were monitored during 2000 and 2001. Herbicides applied on the field were: metolachlor (2184-2254gha^-^1), terbuthylazine (1000-1127gha^-^1) and isoproturon (1000gha^-^1). The VFS reduced both runoff depth (10.2-91.2%) and herbicide losses (85.7-97.9%) in the monitored rainfall events. Total herbicide loss with runoff was low (0.69-3.98gha^-^1 without VFS, less than 0.27gha^-^1 with VFS), but concentrations were sometimes very high, especially of terbuthylazine and isoproturon during the first events after treatment. In these events there was a high probability of exceeding the ecotoxicological endpoint for algae, but the VFS helped to reduce the potential risk. Two VFS effectiveness mechanisms were identified: (i) dilution, and (ii) a ''sponge-like'' effect, which temporarily trapped chemicals inside the VFS before releasing them.
Description:
Herbicide runoff and the effects of a narrow vegetative filter strip (VFS) were studied on an arable field in the low-lying plains of the Veneto Region (north-east Italy). Cultivated plots were compared with and without a 6m wide VFS composed of trees, shrubs and grass. Natural and simulated runoff were monitored during 2000 and 2001. Herbicides applied on the field were: metolachlor (2184-2254gha^-^1), terbuthylazine (1000-1127gha^-^1) and isoproturon (1000gha^-^1). The VFS reduced both runoff depth (10.2-91.2%) and herbicide losses (85.7-97.9%) in the monitored rainfall events. Total herbicide loss with runoff was low (0.69-3.98gha^-^1 without VFS, less than 0.27gha^-^1 with VFS), but concentrations were sometimes very high, especially of terbuthylazine and isoproturon during the first events after treatment. In these events there was a high probability of exceeding the ecotoxicological endpoint for algae, but the VFS helped to reduce the potential risk. Two VFS effectiveness mechanisms were identified: (i) dilution, and (ii) a ''sponge-like'' effect, which temporarily trapped chemicals inside the VFS before releasing them.
