This work was carried out to evaluate the efficacy of the herbicides imazethapyr and chlorimuron-ethyl under pre-sowing conditions in soybean crop. Weed control before sowing and emergence reduction during the crop season were evaluated. The experiment was established in the field soybean had been cultivated, under no tillage, arranged in a randomized block design in a factorial design (4 x 4) + 1. Four herbicide treatments [glyphosate (1.62 kg ha-1); glyphosate (1.62 kg ha-1 ) + imazethapyr (100 g ha-1 ); glyphosate (1.62 kg ha-1 ) + chlorimuron-ethyl (10 g ha¹ ); glyphosate (1.62 kg ha-1 ) + chlorimuron-ethyl (20 g ha-1 )] were combined with four application intervals between herbicide application and sowing time (0, 1, 3 and 7 days). The variety MG/BR 46 (Conquista), with rows spaced 0.50 m was also used as control, with no herbicide application. The addition of the herbicides [imazethapyr (100 g ha-1 ) and chlorimuron-ethyl (10 ou 20 g ha-1)] to glyphosate did not improve weed control nor decreased late re-growth of the following species: Digitaria insularis, Tridax procumbens and Leptochloa filiformis. Three days was the minimum interval in which the three species were not injured by the mechanical sowing process. The herbicide treatments did not affect the number of emerged plants of the following species: Sida santaremnensis, Digitaria insularis, Eleusine indica, Chamaesyce hirta, Bidens pilosa e Senna obtusifolia. Only Althernantela tenella had its emergence rate decreased by herbicide addition to glyphosate, showing pre-sowing efficiency. All the herbicide treatments during pre-sowing increased soybean yield, compared to the control. Herbicide addition to glyphosate did not result in increasing yield.
herbicide; weed; Glycine max; glyphosate
