The Critical Period of Red Root Pigweed (Amaranthus retroflexuxs L.) Control in Green Bean (Phaseolus vulgaris L.)

In order to determine the critical period of redroot pigweed control in green bean, two experiments were conducted in experimental field of Islamic Azad University of Tabriz, Iran, during 2004 and 2005. The experimental design was randomized complete block design with three replications. The treatments included weed infested and weed-free conditions in the same periods. In the both years, in weed-infested experiment, redroot pigweed was seeded immediately after green bean planting and removed after 0, 2, 4, 6, 8, 10 and 14 weeks after green bean emergence (WAE). In weed-free experiment, redroot pigweed was transplanted in green bean plots at 0, 2, 4, 6, 8, 10 and 14 WAE. Results indicated that years had significant effects on all of the traits except pod yield at the first and second harvesting time. All measured traits were affected by different interference regimes, significantly. The early 4 weeks redroot pigweed infestation and weed-free until 10 WAE didn,t decrease green bean above ground biomass. At boths years, the highest yield loss obtained in the full season weed infestation condition. The critical period of redroot pigweed control based on 5 and 10% green bean yield loss were determined as 13 to 60 and 19 to 55 days after emergence, respectively.