تعيين آستانه اقتصادي خسارت تاج خروس ريشه قرمز (Amaranthus retroflexus L.) در مزرعه لوبيا چشم بلبلي (Vigna unguiculata L)

Determination of economic threshold of damage of red root pigweed (Amaranthus retroflexuxs L.) in cow pea (Vigna unguiculata L.) field

In order to determination of economic threshold of damage of red root pigweed in cow pea, an experiment was conducted in agricultural research station of Islamic Azad University of Tabriz, Iran, based on a randomized complete blocks design with three replications. The treatments were red root pigweed interference times at 2, 4, 6, 8, 10 weeks after cow pea emergence until late growth season; full season interference and control weed free plot. Data were analyzed with MSTAT-C soft ware and for mean comparison was used Duncans test. Results showed that the above ground biomass and grain yield of cow pea in control plot was similar to treatment of weed interference at 10 weeks after cow pea emergence until late growth season. Reductions of above ground biomass and yield loss in full season interference were 98.1% and 98.5%, respectively, compared with control. With increasing of weed interference time, pod number in cow pea decreased, significantly. Red root pigweed emergence at density of 8 plants-m"1 of row at early 8 and 10 weeks of cow pea growth stage to later, was caused 10.7% and 2% yield loss, respectively, in comparison with control. With attention to 10% maximum permissible yield loss in cow pea, red root pigweed must be controlled, if it was emerged within a period of 8 weeks of early cow pea growth stage and economic threshold of damage of red root pigweed at studied density level was determined until 8 weeks of early cow pea growth stage.