Long-Term Production Performance and Stability of Alfalfa/Grass Mixtures in the Longdong Loess Plateau of China: Subjected to Various Species Combinations and Seeding Ratios

Stable productivity is the basis for efficient and sustainable use of perennial grasslands, holding both ecological and economic importance. Alfalfa-based mixtures have great potential to achieve this goal. There was limited information on the impact of species combination and seeding ratio on their long-term production performance and stability. We investigated forage yield, quality, and temporal stability over six years in alfalfa (Medicago sativa)/timothy (Phleum pretense) and alfalfa/smooth bromegrass (Bromus inermis) mixtures at varying seeding ratios. Alfalfa/grass mixtures showed a yield advantage over grass monocultures with greater yield at higher alfalfa seeding proportions (50% or more). The mixtures showed advantages in crude protein and neutral detergent fiber. Crude protein content tended to increase with increasing alfalfa seeding proportion, while fiber contents barely changed. As stands grew older, forage yield increased and then declined and showed greater stability in mixtures compared with monocultures. The percentage of alfalfa yield tended to increase over the life of the stand. In contrast, forage quality varied over the life of the stand, with greater variability in mixtures than monocultures. Considering forage yield, quality, and stability across years, smooth bromegrass would be more compatible with alfalfa in a mixture compared to timothy for the Longdong Loess Plateau of China and areas with similar climates.