Dissipation of herbicides in soil and grapes in a South Australian vineyard

The persistence of herbicides applied in vineyards has become a concern in recent years due to their wide use. Investigations into the fate of herbici des in a vineyard in the Barossa Valley, South Australia, have been directe d towards the dissipation of herbicides in soil and on grapes. Concentratio ns of the herbicides, norflurazon, oxadiazon, and oxyfluorfen in soil were monitored following their application in the vineyard. With the exception o f oxyfluorfen, dissipation of these herbicides in the vineyard soil was cha racterised by fast initial loss followed by slow degradation. For oxyfluorf en the dissipation was slow throughout the period of the study. The half-li fe for norflurazon in surface soils varied from 50 days in 1996 to 22 days in 1997 while that for trifluralin was 27 days in 1996 and 30 days in 1997. Oxyfluorfen had a very low dissipation rate with a half-life of 119 days. Oxadiazon had a relatively short half-life of 14 days. Dissipation of the h erbicide residues on grapes in the Roseworthy campus vineyard showed that t rifluralin and oxyfluorfen were not detected 4 days after treatment, while norflurazon and oxadiazon remained on grapes I month after treatment. This study showed that the dissipation of herbicides in soil and on grapes was d ependent on the physicochemical properties of the herbicides and environmen tal conditions. The use of these relatively persistent herbicides in vineya rds has the potential to harm vines and to contaminate grapes and the wine made from them. (C)2000 Elsevier Science B.V. All rights reserved.