growth analysis and evaluation of solar energy conversion in soybean (glycine max (l.) merrill, uberaba) unver field conditions and four doses of metribuzin (0,0;0,35; 0,70 and 1,05 kg i.a.ha-1) were performed in this study. maximum solar energy conversion was 0,75% for pla nts tre ate d wit h 1,05 kg i.a.ha -1 metribuzin. the aver age of solar energy conversion throughout the entire crop cycle were 0,32, 0,31 , 0,32 and 0,33% for the increasing metribuzin doses. in general, the control showed lower figures for all growth values studied than the treated during the vegetative phase. during the reproductive phase, however, they surpassed those tre ated with metribuzin, showing that in the critical period of competition weeds were more harmful than the phytotoxicity produced by metribuzin.