A field experiment was carried out to find out the effect of some herbicides(Pallas, Crash, U46) on the companion weed to three cultivars of the oat crop (Shefa, Hamel, and Pimula) and the yield and its components of these cultivars. The results showed the superiority of the two treatments of spraying weed herbicides (T1 and T2 ) by giving the best results, as they recorded the lowest number of weed plants after 30 days of spraying reached 1.44 and 1.67 plant/m2 . Besides, the lowest weed dry weight was 0.11 and 0.00 g/m2, and the highest inhibition percentage in dry weight was 98.44% and 100.0% of the two treatments, respectively. The treatment T2 was also superior by giving the highest control percentage of 93.28% compared to the comparison treatment T3 (Weedy), which gave the highest weed number after spraying, the lowest control percentage %, the highest weed dry weight, and the lowest inhibition percentage of 21.56 plant/m2 , 0.00%, and 5.00 g/m2 and 0.00% for the above-mentioned traits, respectively. Whereas treatment T2 was superior by giving the best grain yield, which reached 6,590 ton/ha, the highest weight of 1000 seeds was 29.33 g and the highest number of seeds per spike was 52.02 seed/spike. Furthermore, T2 did not differ significantly from the treatment T1 by giving the highest number of spike/m2 amounted to 491.1 and 480.0 spike/m2 for treatments T1 and T2 , respectively, compared with the comparison treatment T3 . It gave the lowest grain yield, the lowest weight of 1000 seeds, the lowest seeds per spike, and the lowest number of spike/m2 , which amounted to 4,819 ton/ha, 22.82 g, 43.27 seed/spike, and 378.8 spike/m2 respectively. The cultivars did not record any response or competitiveness to the companion weed.
