Production and nutritive value of grazed simple and complex forage mixtures

Sustainability of forage production in the Northeast USA is affected by environmental and climatic variability. Complex forage mixtures may be better adapted than simple mixtures to variable environments and produce greater dry matter (DM) yield more evenly throughout the growing season, thereby increasing sustainability of forage production. A grazing trial was set up to evaluate forage production, nutritive value, and botanical composition dynamics of well-adapted and commonly sown forage species. The forage treatments consisted of simple mixtures (two and three species) and complex mixtures (six and nine species). The experiment was mob-grazed with cow-calf (Bos taurus L.) pairs five times each year. Dry matter distribution during the growing season was independent of mixture complexity; it was, instead, influenced mainly by the weather. When averaged across all 3 yr, mixtures containing six species produced greater (P < 0.001) forage yield (9900 kg DM ha(-1)) compared with two-species (8700 kg DM ha(-1)) or three-species mixtures (8400 kg DM ha(-1)). However, forage production varied within species richness groups. In general, regardless of the initial botanical composition, the predominant species in most mixtures by the end of the experiment were orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), and white clover (Ttifolium repens L.). Variation in nutritive value among mixtures was explained mainly by variation in the proportions of grasses and legumes. We conclude that when it comes to large yields and top nutritive value, the most important consideration is the individual species, not the complexity of the mixtures.