Bensulfuron-methyl and metsulfuron-methyl dissipation in water and soil ofrice fields.

Mobility and persistence of two sulfonylurea herbicides, bensulfuron-methyl and metsulfuron-methyl, were studied in order to evaluate the environmenta l risk following application of SIGMA(R) 60DF (58% bensulfuron-methyl and 2 % metsulfuron-methyl) to paddy fields. Trials were carried out in 1994-1996 at three locations in the Italian rice growing area. The results showed th at concentrations of both herbicides in the paddy water decreased to 50% of the initially applied amount after two days. Metsulfuron-methyl was not detected in soil. Bensulfuron-methyl was detecte d in the 0-15 cm depth through the first 5 days of the study (average level : 1.2 mu g kg(-1)) and was undetectable (<1 mu g kg(-1)) 60 days after appl ication. In the 15-30 cm depth the residues reached maximum concentration ( 0.3 mu g kg(-1)) after two days and decreased to undetectable levels 10 day s after the treatment. Bensulfuron-methyl was observed below 30 cm depth at two sites with loamy-sand and silt-loam soils (0.19 and 0.29 mu g kg(-1) r espectively).