alfalfa, alfalfa dry matter yield, herbicides, weed control
Abstract
Field trials were conducted during 2008 – 2010 to evaluate weed control in dormant alfalfa (Medicago sativa L.) with metribuzin, imazetapyr and pronamide. The weed population in all experimental years was consisted mainly of annual winter and spring grass and broadleaf weeds, and some perennial weeds. The number of weed species and weed density increased with the years of alfalfa growing, from second to the fourth year. Weed density in the untreated control plots was 201.0, 217.2 and 240.5 plants per m2 in 2008, 2009 and 2010, respectively. The most dominant weeds were Anthemis cotula, Capsell bursa-pastoris and Taraxacum officinale in 2008, Alopecurus myosuroides and Poa pratensis in 2009 and Millium vernale and Arabidopsis thaliana in 2010. Efficacy of herbicides in control of weeds was ranged of 91.8% (pronamide) to 98.4% (metribuzin 1.0 kg*ha-1) in 2008, 93.1% (imazetapyr) to 97.3% (metribuzin 1.0 kg*ha-1) in 2009 and 92.1% (imazetapyr) to 97.3% (metribuzin 1.0 kg*ha-1) in 2010, respectively. Efficacy of herbicides in control of prevailing weeds during the 3 years field trial period was ranged of 48.5% to 100.0%. No visual alfalfa injured was determined by any rates during the experimental period, and consequently, none of the applied herbicides reduced first-harvest alfalfa yields. Alfalfa yield was markedly affected by herbicide efficacy in all experimental years, particularly in the second year, where yields of herbicide treatments were similar to that of the weed free control.
