Nutritive value and yield of reduced-lignin alfalfa cultivars in monoculture and in binary mixtures with perennial grass

Improvements in alfalfa (Medicago sativa L.) forage nutritive value through reduction in lignin content have the potential to increase economic returns when it is fed to dairy cattle, either as a pure species or in mixture with perennial grasses. Our objective was to assess yield and nutritive value of reduced-lignin alfalfa in monoculture and in binary mixtures with perennial grass. Studies were seeded in the spring of 2016 in Ithaca, NY, Lexington, KY, and Rosemount, MN, and harvested in 2016, 2017 and spring of 2018. WL 355.RR and Hx14376 reduced-lignin alfalfa were seeded as pure stands and in mixture with festulolium [Festulolium loliaceum (Hudson) P.V. Fournier], meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.; syn. Festuca pratensis Huds.; syn. Lolium pratense (Huds.) Darbysh.], or orchardgrass (Dactlyis glomerata L.). The experimental design was a randomized complete block, with a split plot arrangement of cutting management treatments in Ithaca and Lexington, harvesting at alfalfa first bud and first flower stages, and one harvest treatment in Rosemount at first flower. Samples were hand-harvested for dry matter (DM) and nutritive value determinations. Reduced-lignin alfalfa averaged between 11 and 18.5% less lignin over the 3 yr of the study, and averaged between 5.8 and 10.6% greater fiber digestibility, compared to a normal cultivar. Alfalfa response was relatively consistent across regions, but grass response was variable across regions for both grass proportion in mixtures and nutritive value. Perennial grasses grown with alfalfa must be evaluated on a regional basis to produce meaningful results.