Revista Brasileira De Herbicidas 2001; 2(1-2): 49-56
Sequential application of burndown herbicides in the establishment of no-tillage systems in common bean
The sequential application ofherbicides at pre-planting can be used as a strategy to reduce the effect of weed competition with bean plants through the elimination of the first flushes of emergence of weeds. The objective of this research was to evaluate the advantages of sequential application ofburndown herbicides in beans grown under no-tillage, with the elimination of first emergance flushes of weeds prior to planting, and their impacts on the effectiveness of post-emergence herbicides. The experimental design used was randomized blocks with four replications and the treatments in the main plots consisted of bumdown herbicides: sulfosate (396 g/ha a.e.) at 20 days before planting with a supplementary treatment of paraquat (200 g/ha), paraquat + diuron (200 + 100 g/ha), diquat (200 g/ha), paraquat/diuron + diquat (100/50 + 100 g/ha) at planting (sequential application of bumdown – SAB); application of sulfosate + 2,4 0(594 + 720 g/ha a.e.) 10 days before planting (only one bumdown application – OBA) and an untreated control. The sub-plots consisted of post-emergence herbicides: fomesafen + fluazifop-p-butyl (100 + 80 g a.i. ha’), (fomesafen + fluazifop-p-butyl) + bentazon « I00 + 80) + 420 g a.i. ha’) and an untreated control was also included. At 7 days after planting there was no difference between the SAB and OBA, both which controlled up to 85% ofthe weeds. There was no difference between the two post-emergence herbicides, both with effectiveness in the control of weeds up to 98%, independent of applícation ofbumdown herbicides. At the time of planting, the plots with OBA had lower weed density (71 %) than the plots treated with SAB. In addition, at the time of postemergence herbicide application, the density ofweeds was lower (41 %) with the SAB than the OBA plots, with a more favorable stage of development ofweeds for the post-emergence control.
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