Common lambsquarters (Chenopodium album L.) is an important weed of maize fields in Iran. In order to study the effect of common lambsquarters relative time of emergence on maize (Zea mays L.), an experiment was designed with different densities of the weed. The experimental design was split plot based on a randomized completed block design with three replications. The emergence time of lambsquarters was assigned as main plots with three levels: emergence of the weed 14 and 7 days earlier and simultaneously with maize. Density of weed was the subplot treatment with 6 levels: 0, 4, 8, 12, 16 and 20 plants per m2. The results showed that height and leaf area index of maize decreased with earlier emergence time and increasing lambsquarters density, so that 14 days earlier emergence of weed at high densities (16 and 20 plants per m2) was led to maximum reduction. In contrast, height and LAI of lambsquarters increased with earlier emergence time especially at high densities. Common lambsquarters was a stronger competitor when emerged 14 days earlier than maize. Maize yield decreased more than 70% in the 7 and 14 days earlier emergence of lambsquarters at high density. It could be concluded that relative time of weed emergence compare to its density had a greater effect on maize growth. Therefore, controlling lambsquarters before maize emergence at any density is recommended to prevent maize growth and yield loss.

Keywords