DURÉE D’INTERFÉRENCE DU CHIENDENT, Agropyron repens (L.) Beauv. DANS LA LUZERNE, Medicago sativa L.

Abstract

A study was conducted at St-Augustin, Quebec, in 1984 and repeated in 1985 to determine the tolerable period of interference between alfalfa (Medicago sativa L.) and quackgrass (Agropyron repens (L.) Beauv.) during the year of establishment. Glyphosate was used prior to seeding of alfalfa to control quackgrass. Haloxyfop-methyl, a selective grass herbicide, was sprayed at different periods after crop emergence to control quackgrass. This herbicide was applied at 3, 6 and 9 wk after alfalfa emergence. A 3-wk period of interference provided equivalent proportion of alfalfa in forage and the same level of forage quality as the quackgrass-free control. Delaying haloxyfop-methyl treatments to more than 3 wk resulted in an increased proportion of quackgrass in forage which caused a reduction of the protein content and an increase of the cell wall contents (NDF and ADF). Alfalfa density did not differ between 0 and 3 wk of interference of quackgrass, but tended to be reduced with a longer period of interference.Key words: Quackgrass, alfalfa, duration of interference, haloxyfop-methyl, glyphosate, forage quality