Weed control in alfalfa (Medicago sativa L.) is most critical during the establishment period. Good weed control is critical for yield, quality, and stand longevity of the alfalfa crop. Incorporation of livestock manure is a common practice prior to establishment of alfalfa; however the manure may contain viable weed seeds that exacerbate weed problems during establishment.  The development of genetically modified alfalfa with tolerance to the herbicide glyphosate presents an alternative to traditional herbicide programs during establishment.  The objective of this study was to compare weed control during alfalfa establishment between conventional alfalfa varieties and a glyphosate tolerant alfalfa variety.  Alfalfa was established at two locations under furrow irrigation in Colorado.  Establishment year yields and weed biomass will be compared for the first two cuttings.  Forage yield and quality determinations will be used in an economic analysis of the two contrasting establishment approaches.