EVALUATING THE EFFICIENCY OF SOME HERBICIDES IN CONTROLLING WEEDS OF NEWLY PLANTED AND ESTABLISHED ALFALFA
In order to control weeds of alfalfa in the south of Alborz province, a randomized complete block experiment with four replications was conducted in the fields of Iranian Research Institute of Plant Protection located in Meshkindasht, Karaj, during the crop year of 2014-2016. The experimental treatments were one-time application of herbicides including EPTC (5 lit/ha), Metribuzin (750 g/ha), 2,4-DB (3 and 3.5 lit/ha), Bentazon (3 lit/ha) and Imazethapyr (0.5 and 1 lit/ha) on newly planted and established alfalfa, as well as control treatments without weed control and control treatments with manual weeding in all weed seasons. The results showed that the application of herbicides had a significant effect on the weed control efficacy and dry weight of alfalfa; so that, the weed control efficacy were significantly reduced with the application of herbicide treatments. One-time spraying with 2,4-DB (3.5 lit/ha) had a suitable weed control performance. One-time spraying with Metribuzin and Imazethapyr (1 lit/ha) could reduce the dry weight of weeds by 96 and 92% in the first harvest, 89 and 86% in the second harvest. Imazethapyr and EPTC herbicides did not harm alfalfa and significantly increased its yield. Although Metribuzin had an effective performance in controlling weeds, it caused plant burning and damage in the first harvest. One-time spraying with Imazethapyr (1 lit/ha and 0.5 lit/ha) had the highest dry weight yield. These treatments were able to increase the dry weight of alfalfa by 28 and 32% in the first harvest, 22 and 31% in the second harvest. Therefore, due to weed control efficiency and increased yield, it is recommended to apply one-time spraying with Imazethapyr herbicide (1 lit/ha).