Yield Dynamics of Canopy Components in Alfalfa‐Grass Mixtures

Relationships between alfalfa ( Medicago sativa L.) and associated grasses in a plant community are complex. A concern has developed whether alfalfa was, in fact, benefiting from grass association. A field study was conducted to describe the changes in canopy components of alfalfa‐reed canarygrass ( Phalaris arundinacea L.) and alfalfa‐orchardgrass ( Dactylis glomerata L.) mixtures. Alfalfa‐grass mixtures of one row of grass between two rows of alfalfa and one row of alfalfa between two rows of grass were planted in a repeating pattern. Monocultures of each species and four binary mixtures were sampled for total, alfalfa and grass component, and stratified alfalfa yields were measured at 10, 20, 30, 40, and 50 d of spring and summer regrowth for 2 yr. Planting pattern, grass species and season of growth affected botanical composition and yield of alfalfa‐grass mixtures. Alfalfa‐grass mixtures yielded more than alfalfa monocultures during only one spring growth cycle. During summer regrowth, alfalfa‐grass mixtures were less productive than alfalfa monocultures. In spring, reed canarygrass accounted for a greater proportion of the total yield than orchardgrass, whereas the two grasses were similar during summer. Grass yields of mixtures were not affected by alfalfa association. The results of this study suggest that alfalfa‐grass mixtures offer little yield advantage over alfalfa monocultures when harvested as hay.