Forage dry matter yield, nutritive value, and botanical composition of diverse perennial forage species mixtures

This field study examined the forage dry matter (DM) yields, nutritive values, and botanical compositions of 29 perennial forage mixtures and monoculture grasses over 3 consecutive production years in Fairview, Alberta, Canada. Treatments consisted of 6 simple binary mixtures (grass-legume), 18 diversified mixtures (each with 3 or more species, comprising grass-legume, grass-only, and legume-only mixtures), and 5 monoculture grasses (single species) as references. The forage DM yields of grass–legume and legume-only mixtures were the highest during the first (2.4 Mg ha−1) and third (4.9 Mg ha−1) production years, with monoculture meadow bromegrass [Bromopsis biebersteinii (Roem. & Schult.) Holub] producing the highest DM yield (4.8 Mg ha−1) in the second year of production. Averaged across the 3-year period, grass–legume and legume-only mixtures had greater DM yields compared to monoculture grasses or grass-only mixtures. Legume mixtures had the highest crude protein (CP) followed by grass–legume mixtures. The grass–legume mixtures had the lowest neutral detergent fiber (NDF) and acid detergent fiber (ADF). Total digestible nutrients (TDN) were highest in a five‑species blend of a grass-only mixture, whereas NDF digestibility over 48 h was highest in monoculture grasses and grass-only mixtures. Among legumes, alfalfa (Medicago sativa L.) dominated the botanical composition relative to sainfoin (Onobrychis viciifolia Scop.), cicer milkvetch (Astragulus cicer L.), and birdsfoot trefoil (Lotus corniculatus L.), whereas the AC Success hybrid bromegrass (Bromus spp.) was the dominant grass cultivar within the forage mixtures. Highly diversified mixtures, including six- and eight‑species blends , suppressed weeds better than simpler forage combinations.