To evaluate the effect of different corn / redroot pigweed densities and reduced herbicide doses of 2, 4- D+ MCPA on corn growth and yield and control of redroot pigweed, a field experiment were conducted at the Agricultural Research Station, Ferdowsi University of Mashhad, in 2007. A strip block design on the basis of randomized comlete block design with three replications was applied. The experiment consisted of three factors: weed density (3, 6, 9 and 12 plant⁄m 2) as vertical factor, herbicide dose (0, 50 and 100 % of recommended doses) as horizontal factor and crop density (7, 9 and 11 plant⁄m 2) which splitted on vertical factor. Results showed that herbicide application reduced weed dry weight and leaf area index (LAI). In contrast, corn dry weight and LAI increased as herbicide application doses increased. Corn grain yield and yield components increased significantly by increasing corn density. The herbicide efficiency increased, when herbicide was applied to corn of upper crop density and corn yield losses decreased. The increase in herbicide efficiency was significant in reduced dose treatment, but in recommended dose a little increase was observed. Corn grain and biological yield, grain numbers per row, 100 seed weight and harvest index decreased significantly by
increasing pigweed density, but rows number per cob was not affected. The results of this research indicated that herbicide dose could be decreased by using high corn density, without significant decrease in grain yield. |
