Harvest frequency and cultivar influence on yield and protein of alfalfa-ryegrass mixtures

Binary mixtures of alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) are commonly grown for forage in the U.S. Northeast. The competitiveness of ryegrass with alfalfa as modified by management practices has not been extensively studied. Two experiments were conducted to measure the influence of harvest frequency and ryegrass ploidy level on production, botanical composition, and crude protein concentration of alfalfa-ryegrass mixtures. The first experiment used six replicates of a factorial treatment structure (three ryegrass cultivars x three harvest cycles) in a split-plot design. The second experiment used three replicates of three cultivars x three harvest treatments. Increasing the length of the harvest cycle from 20 to 40 d increased alfalfa and total dry matter production (10.1 to 14.9 Mg ha(-1)) while decreasing ryegrass production and proportion (49 to 18%) of grass in the stand. Ryegrass was nearly eliminated from the stand at the 40-d harvest cycle, but when the cutting cycle was changed to 20 d the next year, it became productive and contributed one-fourth to one-half of the total forage yield. Alfalfa, which had low productivity (7.3 to 8.4 Mg ha(-1)) in a 20-d cycle, became very productive (16.4 to 17.4 Mg ha(-1)) when the cycle was changed to 40 d the next year. Crude protein concentration in alfalfa decreased from 248 to 200 g kg(-1) as harvest cycle increased from 20 to 40 d. Ryegrass crude protein increased from 163 to 184 g kg(-1) as harvest cycle increased. Frances and Diplomat perennial turfgrass ryegrasses were as productive and persistent as Citadel perennial forage ryegrass in binary mixtures with alfalfa.