ABSTRACT
Abstract Three field trials were carried out in order to assess the effects of the traditional and no-tillage system upon runoff and herbicide transport. Two were conducted in a wheat crop under rainfed conditions, during the winters of 1993/94 and 1994/95, at two different sites on a Haplic Luvisol, and the herbicide used was isoproturon. The third trial, corn irrigated with a center pivot, was carried out in the summer of 1994, on a Gleyic Luvisol, and the herbicides under study were atrazine and metolachlor. In all trials, the total runoff volume and sediment yield was higher under traditional tillage. The total amount of herbicides found in the runoff water was higher under the traditional tillage treatment, although the concentration of the herbicides in the runoff water from the first rainfall or irrigation/runoff event had been higher under the notillage treatment. The concentration of all the herbicides in the runoff water was considerably higher in the first and second rainfall or irrigation/runoff event, decreasing rapidly in subsequent events. The results show that care should be taken when adopting the no-tillage system since the residues and vegetation at the field surface may intercept much of the applied pesticides, where they are bound weakly and may be washed off easily. Keywords:, Herbicides, no-tillage, runoff, sediments, tillage.
