The weed community affects yield and quality of soybean (Glycine max (L.) Merr.)

BACKGROUND: The relationship between the weed community and soybean (Glycine max (L.) Merr.) seed yield and quality was assessed in two experiments in Illinois, USA. In one field different proportions of target weeds (Ambrosia trifida L., Amaranthus rudis J. Sauer, and Setaria faberi F. Herrm) were sown into experimental plots, and the other field was naturally infested with these and other weeds. The composition of the weed communities in both fields was compared to soybean yield, biomass, canopy cover and quality (% protein, oil, relative water content, and seed weight) using non-metric dimensional scaling ordination. RESULTS: In the experimentally sown plots, low yield and low quality soybeans were harvested from plots dominated by the target weeds, particularly A. trifida, and a suite of subordinate volunteers. In the naturally infested field, highest soybean protein was associated with S. faberi early in the season and Ambrosia artemisiifolia and Ipomea hederacea later in the season, and low amounts of A. rudis throughout the growing season. CONCLUSION: Similar results from the two experiments indicate that soybean seed yield and quality are affected by the composition of the weed community. Producers need to manage the weed community to optimize seed quality. (c) 2007 Society of Chemical Industry.