Evaluation of chemical control of broad-leaved weeds in new seeded alfalfa (Medicago sativa L.)

In order to study of the efficacy of herbicides in weed control of new seeded alfalfa, an experiment was conducted in Hamedan and Yazd cities, Iran during 2009-2010. The treatments were Bentazone (Bazagran) (SL 48%) two, three and four L.ha-1, 2,4-DB (Butress) (EC 42.3%) 2.5, 2.8, 3.1 and 3.5 L.ha-1, Imazethapyr (Pursuit) (SL 10%) 0.4, 0.7 and one L/ha and without herbicide control treatment. The herbicides effect on alfalfa biomass and the biomass and density of weeds was studied during three cuttings. In Yazd, 2,4-DB 3.5 L.ha-1 was the best treartment for controlling weeds and increasing alfalfa biomass. 2,4-DB 3.5 and 2.8 L.ha-1 controled the density and biomass of Malva and Lactuca to 100 and 88 percent, respectively. In Hamedan, herbicides treatments had no phytotoxocity on alfalfa. Only Bentazone caused chlorosis in alfalfa that recovered that after one to two weeks. 2,4-DB not only was suitable in control ling broad leaves weeds, but also was successful in field bindweed control. Overall. 2,4-DB seems to be an efficient herbicide