Abstract

Field experiment was conducted at Karaj, Iran to evaluate the growth and yield responses of winter wheat to
various densities of wild barley and nitrogen (N) application rates. The experimental design was split-plot with 3
replications. The main factor was four N levels of 0, 130, 260, and 390 kg Urea per ha and the sub factor was weed
densities. Results showed that in unfertilized plots, wild barley densities of 80 and 160 plants per sq. meter
significantly decreased wheat plant height, LAI and tillers. In comparison to excess N and N deficiency treatments,
the optimal N rate decreased wheat LAI losses at weed densities of 80 and 160 plants per sq. m. Wild barley had
greater plant height and the number of tillers per plant at densities of 20 and 40 plants per sq. meter. At 130 kg N
per ha, weed densities of 20, 40, and 80 plants per sq. meter did not reduce the number of crop ear compared to
hand-weeded plots. On unfertilized plots with 40, 80, and 160 weed plants per sq. meter, the reduction in number
of grains per ear were 18 and 38%, respectively. Nitrogen rates of 130 and 260 kg per ha increased crop and weed
GNCs, whereas their STNCs were increased by N rate up to of 390 kg per ha. Added N resulted in higher winter
wheat ANUE compared to weed ANUE.

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