EVALUATION OF DIFFERENT HERBICIDES AND RATES OF APPLICATION EFFECTIVENESS ON WEED CONTROL IN MAIZE

Two field experiments were conducted with three replicates according to RCBD at the experimental field of Dept. of Field Crop Sciences - College of Agriculture - University of Baghdad during fall and spring seasons of 2001 to evaluate the effectiveness of herbicides; Imazamox, Atrazine, Bentazine, Isoxafutol, Propaquizefop and Clomayone; and their application rates on maize.The results showed that Atrazine (H69 and H68) at 3.2 kg.ha(-1), after 60 days, was significantly superior to other herbicides by giving less weed population during spring and fall seasons (2.5 and 1.7 plant.m(-2) respectively), while control treatment gave the highest average (16.2 and 11.8 plant.m(-2) respectively). Thus in comparion with control, number of weed were reduced by 84.5% and 85.5% respectively. Using 0.192 kg.h(-1) of Clomazon during spring season gave less average of weed number (3.4 plant.m(-2)) after 90 days, whereas the control gave higher average (25.1 plant.m(-2)), thus the weeds population were reduced by 86.46% in comparion with control. Herbicide behavior was different during fall season. Atrazine (H68) at 3.2 kg.ha(-1) gave less weed population (2.9 plant. m-(2)) while the weed population of the control was 19.9 plant.m(-2), so the weed population was reduced by 85.4. At harvest time, Isoxfotol at 105 kg. ha(-1) resulted in less weed population (17.8 plant.m(-2)), while Atrazine at 2.4 kg.ha(-1) resulted in less weed population during fall season (9.6 plant.m(-2)). From the results above, it was conclude that there were many differences in herbicide behavior in the percentage of weed number reduction after 60 and 90 days and at harvest time. These results confirm declining effectiveness of herbicide 90 days after sowing.