Interference of lambsquarters (Chenopodium album) with grain corn, cultivar 604

An experiment was carried out to evaluate the competitive effects of lambsquarters (Chenopodium album L.) on corn (Zea mays L.) grain yield, in Tabriz in 2008. Factorial experiment was established on randomized complete block design with three replications. Factors were five weed densities (1, 4, 8, 12 and 16 weeds m-1 of row) and four relative times of weed emergence (emerged with corn; 10, 20 and 30 days after corn emergence) including a weed free. Interaction of lambsquarters density and time of emergence on weed leaf area index at 75 days after corn emergence was significant. Leaf area index in weed ranged from in the highest to 0.19 at the lowest competitive condition. With increasing of weed density and delaying in emergence time its biomass reduced. Weed competition was caused a significant loss in grain yield and time of weed emergence is more effective than weed density. Yield loss of corn at different weed emergence times were 64%, 38%, 15%, 8%; and at different weed densities were zero, 23%, 35%, 46%, 53%, respectively, compared with control. Emergence of minimum four lambsquarters plants per meter of corn row before 20 days after crop emergence and competition until late growth season was the economical threshold of this weed.