Cultivar and Fall Dormancy Affect Alfalfa-grass Yield and Persistence in a Temperate Environment

In the humid temperate area of Argentina, most farmers use alfalfa (Medicago sativa) in grass-legume pastures, but there is little information on how alfalfa cultivars with different fall dormancy (FD) ratings may affect forage production. The objective was to compare the effect of a range of alfalfa cultivars from moderately dormant to non-dormant on forage production over three years when seeded with orchardgrass (Dactylis glomerata). Eleven alfalfa cultivars grouped by FD as moderately dormant (MD), semi-dormant (SD), moderately non-dormant (MN), and non-dormant (ND) were compared for three years under rotational grazing with dairy cows. Alfalfa yield in the first year was not different between FD groups, but there was an important effect of FD in production in the second and third year. The MN group was significantly more productive than MD, and SD and ND had intermediate yields. There were also significant differences among cultivars within FD groups. Orchardgrass yield was independent of the associated alfalfa cultivar, indicating that a higher yield of the alfalfa cultivar resulted in a higher pasture yield. After three years the MN group had better persistence than MD. Most productive and persistent cultivars of SD to ND groups can be used for grazing a grass-legume pasture, at least for a medium-term pasture phase in cropping rotations.