The experiment was carried out on a Dark Red Latosol, with 53% clay and 4,5% organic matter, to study the ef ficiency and selectivity of post emergence her bicides on soybean cv União. The her bicides were applied when the weeds had 3 to 5 leaves. The following treatments (kg a.i./ha) wer e used: tank mixes of alloxydim - Na, at 1,125, and of sethoxydim, at 0,221, with benta zon, at 0,72; combination of diclofop, at 0,84, with acifluorfen, at 0,224; diclo-fop, sethoxydim, 0,147, 0,184 and 0,221, fluaz ifop - but yl, 0,25 and 0,37, CGA 82725, 0,35, all in combi nat ion with benta zon at 0,72. As che ck treatments, oryza lin + met ribuzin (1,125 + 0,42), hoeing and no hoeing wer e used. The grass weeds her bicides, for the combinat ions, wer e applied 3 days after aciflu orfen or bentazon. The control of Brachiaria plantaginea Link. Hitch. and of Ehcinochloa crusgalli L. Beauv. was defficient only for the treatments with alloxydim - Na. Digitaria sanguinalis L. Scop. was not controled by the treatments with diclo - fop, alloxydim - Na and with the lower dosage of sethoxydim. Among the dicotiledoneous, only Sida rhombifolia L. was not controlled by acifluorfen. The tank mix of alloxydim - Na + bentazon decreased the effect of the grass herbicide, while sethoxydim + bentazon did not show this antagonism. Phytotoxicity was greater in the treament diclofop with acifluorfen. Soybean plant height and plant population, seemed not to be influen - cend by the herbicides. The highest yield (2.416 kg/ha), which was 5,4% higher than the hand hoed treatment (2.292 kg/ha), was obtained with fluazifop - butyl in its higher dosage, plus bentazon. The treatments oryzalin + metribuzin, with the two higher dosages of sethoxydim and its mixture, and the lower dosage of fluazifop - butyl were also superior to hand hoeing.
Post emergence herbicides; soybean; control; selectivity