INTERACTION OF WHITE BEAN (PHASEOLUS-VULGARIS L) CULTIVARS, ROW SPACING, AND SEEDING DENSITY WITH ANNUAL WEEDS

Field experiments were conducted at the Elora Research Station, Elora, Ontario, in 1988 and 1989 to quantify the inherent competitive abilit y of three white bean cultivars: OAC Gryphon, OAC Sprint, and OAC Lase r growing with a naturally occurring population of annual weeds. An at tempt was made to increase the competitive ability of these cultivars by altering row spacing and seeding density. Uncontrolled populations of weeds reduced white bean yields by 70%. OAC Gryphon and OAC Laser r educed weed biomass by 10 to 35% compared to OAC Sprint. The ability o f cultivars to reduce weed biomass was further enhanced in medium and narrow rows compared to traditional wide rows. Cultivar, row spacing, and seeding density combinations which maximized leaf area index when grown under weedy conditions also had significantly less weed biomass. However, cultivar selection, row spacing, and seeding density did not reduce weed density. A significant negative correlation was observed between weed biomass accumulation and final yield of white bean. For e ach kg ha-1 increase in weed biomass the corresponding white bean yiel d loss averaged 0.380 kg ha-1. Season-long weed competition significan tly reduced total number of pods per plant, number of seeds per pod, a nd 100-seed weight.