Effect of seed planting depth and sowing time on winter wild oat populations (Avena ludoviciana) and wheat competition (Triticum aestivum)

Wild oat is considered as one of the most problematic weeds in cereals due to compatibility with ecological conditions and competition. The emergence pattern of this weed allows its presence and competition with wheat throughout the growing season. To evaluate the effect of sowing time and depth on wheat and winter wild oat competition, a field experiment was conducted in a split-split plot designe with three replications in 2016-2017. Main plots were two sowing dates of wheat and wild oat (November 10 and December 15), subplots were six wild oat populations (Shiraz, Kurdistan, Mashhad, Kermanshah, Karaj and Ahvaz) and sub-sub-plot were seed sowing depth of wild oats (2 and 5 cm). The results showed that emergence rate of wheat was higher than wild oat populations in both sowing dates. In November sowing date treatment, wheat produced more individual weight in competition with wild oat. Competition with wild oat was effective on wheat height. Ahvaz population had the greatest (wheat height 74.16 cm) effect on reducing wheat height in November sowing date. In December sowing date, Karaj population had the least (wheat height 89.66 cm) effect on reducing wheat height. Depending on sowing date and the population of wild oat, seed depth had different effects, so that in November sowing date and 5 cm depth, wild oat biomass (205.212 g/m2) was less than December (379.294 g/m2). Also, Karaj and Ahvaz populations had the lowest seed number in competition with wheat. Generally, the sowing date and seed planting depth of wild oat populations were effective on emergence model and competitive ability of this weed with wheat. These results we can be used to plan for the application of weed management methods such as selection of tillage systems.