Technical Abstract: Weed control is the biggest obstacle for farmers involved in organic soybean production. One answer to this problem is development of new varieties that compete better with weeds. The most likely approach to more competitive varieties is selection for those that cover the ground sooner after emergence and shade out weeds better. However, to do this, soybean breeders need good screening protocols to identify the most competitive genotypes. This purpose study was to compare two screening methods, determine which was best, and also to determine the optimum time after emergence for screening. The two methods were measurement of a) percent light interception by a soybean canopy using light sensors under the canopy, and b) percent ground cover using overhead photography. In 2007 and 2008 we tested two screening tactics to non-destructively estimate canopy coverage during the first 7 weeks after emergence, the critical period for weed competition. Overhead photography at three and five weeks after emergence and light interception measurements at four and six weeks after emergence were compared in ability to predict soybean and weed biomass at the end of the critical period for weed competition. Photograph digital image processing techniques were compared. Overhead photography at five weeks after emergence was most effective at predicting weed free soybean biomass but overhead photography at three weeks after emergence was best able to predict weed biomass associated with soybean genotypes at the end of the critical period for weed competition.