Interference Effect of Redroot Pigweed (Amaranthus retroflexus L.) on Maize (Zea mays L.) Yield and its Morphological Characteristics

Maize is one of the important cereal crops in Iran. Moghan, in Ardabil province, is an appropriate region to grow it in the country. Redroot pigweed (Amaranthus retroflexus L.) is one of the major noxious weed in maize fields worldwide and also in Iran. To study the interference of effect of this weed on maize seed yield and its morphological characteristics, a factorial experiment based on randomized complete block design with three replications was carried out at the research field of Agricultural and Natural Resources Research Center of Ardabil (Moghan) in 2012. The experimental factors were maize plant densities with four levels (70000, 75000, 80000 and 85000 plant.ha-1) and redroot pigweed densities with four levels (0, 4, 8 and 12 plant/m per row). The results showed that increasing density of maize and redroot pigweed, grain yield, biological yield and chlorophyll content of maize leaves were significantly reduced. The highest grain yield (11.88 t.ha-1) at density corn of 80000 plants.ha-1 of maize under weed free condition and lowest grain yield (7.92 t.ha-1) at maize density of 75000 plants.ha-1 with the presence of the 12 plant/m per row of redroot pigweed. The highest biomass of redroot pigweed (497.8 g/m per row) was produced at density of 85000 plants.ha-1 of maize with the presence of the 12 plant/m per row of redroot pigweed. Generally, the results of this research showed that 80000 plants.ha-1 of maize resulted in highest control of redroot pigweed and grain yield.