The effects of weed control measures in established alfalfa (Medicago sativa L.) on forage yield and quality were investigated at three sites with varying alfalfa densities and weed populations. Herbicide treatments were 0.56 and 1.12 kg/ha metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] applied in fall or spring, respectively, 1.68 kg/ha pronamide [3,5-dichloro (N-1,1-dimethyl-2-propynyl)benzamide] applied in fall, and combinations of these treatments. First-harvest forage yields (weeds plus alfalfa) were either reduced or unchanged by herbicide treatments. Total forage yield was not altered by the herbicide treatments, but first-harvest and total alfalfa yield as well as first-harvest forage protein content were increased by several treatments, depending on stand density and weed pressure. Little effect was observed on in vitro digestible dry matter or acid detergent fiber content.
