Evaluation of the biological activity of 16 sulfonylureas in soil by Nasturtium officinale R. Br. bioassay

Biological activity of 16 sulfonylureas, of which 13 commercialized in Italy, was evaluated in soil using Nasturtium officinale R. Br. as indicator plant. The data confirmed the extraordinary biological activity of this class of herbicides which presented ED50 (dose required to give 50% reduction of the plant fresh weight with respect to the control) values ranging between 0.2 and 20 ng g(-1). However, the phytotoxicity strongly varied as a function of the active ingredients. The most active sulfonylureas in soil were those introduced into the market between 1982 and 1990. Viceversa, most of the active ingredients registered after 1990 showed a 4-50 fold lower activity in soil. These newer sulfonylureas show lower risk of carry over and environmental pollution. Finally, the bioassay with N. officinale confirmed its potentiality as an alternative analytical procedure for the detection of this class of herbicides in soil at ng g(-1) concentration levels.