Effect of Weed Interference Period on Forage Yield of Maize (Zea mays cv. 454) as Second Crop

Controling weeds at their critical periods of growth leads to low production costs and injurious effects of using chemical weed controling methods. In this experiment we studied the timinig effects of weed control (interference of weeds after 20, 40 and 60 days and complete control of weeds) and weed interference periods for 20, 40 and 60 days after planting and complete interference) on growth and yield of forage maize CV. 454. The experiment was conducted incomplete randomized blocks design with three replications at the Research Farm of Islamic Azad University of Tabriz Branch in 2013. According to the results, maintenaning the farm for 40 and 60 days under weed interference after 20 days prevented reduction of maize biomass, while weeds interference after 20 days, weed interference and controling weeds after 40 and 60 days resulted in 41.2%, 35%, 25% and 32.5% reduction of forage maize biomass, respectively. Reduction in fresh weight of corn and fresh weight of leaf and stem were also observed due to interference of weeds after 20 days. If weeds are controlled after 60 days, reduction of corn weight and fresh weight of stem will also results in reduction of biomass. Also, if weeds are controlled after 40 days, stem fresh weight of maize will result in biomass reduction. Corn traits were affected by weeds control treatments. Being affected by treatments of weeds interference after 20 days, weeds non-interference, controlling weeds after 40 and 60 days, the height of corn was reduced by 29.9%, 41.4%, 27.6% and 37.2%, respectively. The stem diameter demonstrated a significant reduction, although it was only affected by treatments of weeds interference and weeds control after 60 days. Based on the results of this study, it may be suggested that controling weeds during initial 20-60 days of maize growth would prevent the undesirable effect of weeds on growth, production and biomass production of maize and also results in production costs.