Control of Yellow Nutsedge (Cyperus esculentus) and Other Weeds Before Summer Planting of Alfalfa (Medicago sativa)

After land was plowed in the spring and prepared for planting, yellow nutsedge (Cyperus esculentus L.) was allowed to develop to heights of 10 to 12 and 20 to 25 cm. Either glyphosate [N-(phosphonomethyl)glycine] or paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was applied to emerged yellow nutsedge and other annual weeds at rates of 0.5, 1, 2, and 4 kg/ha. Half of the plots were double-disked 3 days after herbicide applications, and then all plots were planted with alfalfa (Medicago sativa L. ‘Cayuga’). Disking alone and application of glyphosate or paraquat alone did not satisfactorily control all weeds. However, the combination of a herbicide and disking controlled weeds enough to allow excellent establishment of alfalfa. In the year after establishment, the first cutting yields from the better combination treatments ranged from 3000 to 4400 kg/ha, which is normal for mid- to late-summer plantings in the region. Glyphosate was better than paraquat for control of grass weeds. Paraquat approached glyphosate in effectiveness when a supplemental disking treatment was added. Disking was as effective as the herbicide treatments for control of yellow nutsedge but not for control of broadleaf or annual grass weeds.