Due to the great losses caused by weeds to the crop, it is necessary to continue testing new herbicides that may be more efficient than the herbicides used that can reduce competition between weeds and crops, Therefore, a field experiment was carried out in the experimental field of the Department of Field Crops, College of Agricultural Engineering Sciences, University of Baghdad (Al-Jadriya) during the winter season of 2021-22 in order to evaluate the efficiency of the herbicide H-199 and compare it with some herbicides used in controlling companion weed to three cultivars of wheat and its effect in the yield and its components. The experiment was applied according to the randomized complete block design with split-plot arrangement with four replicates, as the cultivars (IPA 99, Sham 6 and Rasheed) represented the main plots, while the herbicides (H-199, Chevalier, Pallas, Atlantis, and weedy treatment) represented the sub-plots. The results showed the superiority of Pallas by giving the best results, it gave the lowest weed density after 30, 60 and 90 days of application the herbicide, which amounted to 0.2, 4.3 and 0.2 plants/m2, respectively, and the highest weed control percentage amounted to 99.85%, compared with the control treatment, which gave the highest weed density (116.3, 171.0 and 168.7 plants/m2) and the lowest weed control percentage (0.00%), which was reflected in the yield components. Pallas gave the highest number of spikes, the highest number of grains per spike, the highest grain yield, and the highest harvest index, which reached 314.6 spikes/m2, 55.99 grains/spike, 4.597 t/ha and 32.08%, respectively, compared with the weedy that gave the lowest number of spikes (122.7 spikes/m2), the lowest number of grains per spike (33.87 grains/spike), the lowest grain yield (0.937 t/ha) and the lowest harvest index (19.69%). Moreover, Atlantis gave the highest weight of 1000 grains, which was 26.35 g, compared with the weedy treatment. which gave the lowest weight of 1000 grains (22.80 g), The results also showed the superiority of the Sham 6 cultivar, as it gave the lowest weed density, the highest number of spikes, the highest weight of 1000 grains, the highest grain yield and the highest harvest index. We conclude that Pallas and Sham 6 (cultivar) recorded the best results.
