Winter Wheat (Triticum aestivum L.) Nitrogen Yields as Affected by Wild Barley (Hordeum spontaneum Koch) Population Densities and Nitrogen

Field experiments were conducted to evaluate the wheat nitrogen yields responses to densities of wild barley and nitrogen (N) levels. The experimental designs were split-plot with 3 replications. The main factor was nitrogen levels of 0, 130, 260, and 390 kg ha-1 and the sub factor was different wild barley densities. At Shiraz, crop GNY, STNY, and NHI decreased with increasing weed density and increased with increasing N levels. Without N, weed GNY was more than that of crop at all weed densities indicating more competitive ability of weed than crop. Crop and weed ANUE values showed that wheat used nitrogen more efficiently than wild barley because of its higher potential for grain production. Wild barley showed higher ANRE than wheat because of its higher GNC and STNC. At Karaj, 130 and 260 kg N ha-1 increased crop and weed GNCs, whereas both plant STNCs were increased by N rate up to of 390 kg ha-1. Maximum crop and weed BNYs were obtained at 260 kg N ha-1. On unfertilized plots, weed GNY was more than that of crop. With and without N, wheat BNY was more than that of wild barley, whereas wild barley NHI was higher than that of wheat. Each level of added N resulted in higher wheat ANUE compared to wild barley ANUE. Wild barley took up more N than wheat at all N application rates