تأثير تداخل زماني علف هرز تاج خروس ريشه قرمز (Amaranthus retroflexus L) بر عملكرد لوبيا چشم بلبلي (Vigna unguiculata L)

Effects of red root pigweed, Amaranthus retroflexuxs L. interference times on yield of cowpea, Vigna unguiculata L

Red root pigweed is the third dicotyledonous dominant weed of crops in the world from view point of yield loss. In order to quantify the interaction of cowpea yield to different times of red root pigweed (RP) interference, an experiment was conducted at research field of Islamic Azad University of Tabriz, Iran, based on randomized complete block design with three replications. The treatments were RP interference times (2, 4, 6, 8, 10 weeks after cowpea emergence), full season interference and weed free plot as control. In all treatments, RP was seeded immediately after cowpea planting and removed after treatment levels. Analysis of variance indicated that effect of treatments on all traits was significant. The highest (79%) and the lowest (25%) green cover percentages were measured at flowering stage in weed free, and full season interference treatments, respectively. Cowpea biomass in weed free plot (3895 kg haʹ1) was similar to treatment of two weekly RP interference in early growth stage of cowpea (3889 kg haʹ1). With increasing RP interference time, pod numbers in each plant decreased more than other traits. The highest reduction in thousands seed weight (70.13%) compared to control was observed in full season RP interference. Crop yield in full season RP interference treatment decreased up to 98.49% compared to control. With considering of maximum acceptable yield loss (10%) and results of this research, interference time of RP must not be longer than 4 weeks in early growth stage of green bean.