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Performance of Alfalfa (Medicago sativa L.) Blends Consisting of Long- and Short-Lived Varieties¹

In the United States, blends (seed mixtures) of alfalfa (Medicago sativa L.) varieties were planted on approximately 8.75% of the acreage planted to alfalfa in 1969. Combinations of short-lived highly productive varieties and long-lived moderately productive varieties are assumed to be more productive than the long-lived variety in the early years of the stand and to provide enough plants for an adequate stand after the short-lived plants have died. To test these assumptions, blends containing a mixture of one long-lived variety, ‘Vernal,’ and two short-lived varieties, ‘Moapa’ and ‘Stride,’ were seeded at 4.5, 9.0, 13.5, and 18.0 kg/ha in April and August. Hay yields were determined through four harvest seasons. Stand counts were made in the 1st and 4th harvest years following the August planting.

Inclusion of Stride, a winter-hardy, wilt-susceptible variety, in a blend with Vernal increased yield 1.7 mt/ha in the 1st harvest year over Vernal seeded alone. Stride-Vernal blend yields were not significantly different (5% level) from Vernal seeded alone in the second harvest year, but significantly less than Vernal in the third and fourth harvest years. Moapa plants died in the first whiter after seeding. First harvest-year yields of Moapa- Vernal blends were significantly less than Vernal alone. Differences in the second production year were smaller and in the 3rd and 4th harvest years blends containing 33% Moapa seed yielded about the same as Vernal seeded alone (20.35 vs 20.75 mt/ha).

After the Moapa plants died in the first winter after seeding, the remaining Vernal plants gave a stand nearly as productive as Vernal seeded alone. When the Stride plants died after 2 or 3 years the remaining stand of Vernal plants was less productive than Vernal seeded alone. There was little advantage of the blends studied over a single well-adapted variety.

Key Words: Vernal • Moapa • Stride • Bacterial wilt • Winter-hardy

² Professor of Crop Production and Professor of Plant Breeding and Genetics.

Received for publication April 13, 1972.