Screening Tactics for Identifying Competitive Soybean Genotypes

Abstract

Weed control is the biggest obstacle for farmers transitioning to organic soybean production. The breeding of competitive cultivars may provide organic soybean producers with another weed-management tactic. Soybean breeders need screening protocols to identify competitive genotypes. In 2007 and 2008, we tested two screening tactics to nondestructively estimate canopy coverage during the critical period for weed competition. Overhead photography at 3 and 5 weeks after emergence and light interception measurements at 4 and 6 weeks after emergence were compared in their ability to predict soybean and weed biomass at the end of the critical period for weed competition. Photographic digital image processing techniques were compared. Overhead photography at 5 weeks after emergence was most effective at predicting weed-free soybean biomass but overhead photography at 3 weeks after emergence was best able to predict weed biomass associated with soybean genotypes at the end of the critical period for weed competition.