Seedling Emergence of Yellow‐Flowered Alfalfa as Influenced by Seed Weight and Planting Depth

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AbstractYellow‐flowered alfalfa [Medicago sativa L. subsp. falcata (L.) Arcangeli] is well‐adapted to rangeland sites in the central and northern Great Plains, but its early seedlings vigor is poor compared to that of purple‐flowered alfalfa (M. sativa L. subsp. sativa). The objectives of this study were to (i) develop germplasms with a high percentage of falcata traits and (ii) determine the effect of seed weight and depth of planting on seedling emergence. Germplasm with 18 seed‐weight classes (1.0 to 2.1 g/l000 seeds) was developed and evaluated for seedling emergence from a 1.9‐cm depth of planting in a Nunn clay loam soil (fine, montmorillonitic, mesic Aridic Argiustolls) on two dates of planting at Fort Collins, CO, in 1986. Seed weight was significantly (P ≤ 0.01) correlated with seedling emergence at both the first (r = 0.69) and second (r = 0.79) dates of planting. The 18 classes were consolidated into six classes whose mean seed weights were 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 g/1000 seeds. The six classes were evaluated for seedling emergence from 1.3‐, 2.5‐, and 3.8‐cm depths of planting at Fort Collins, from 1987 through 1990. The six seed‐weight classes and three depths of planting differed significantly (P ≤ 0.05 or ≤ 0.01) for seedling emergence at each of six planting dates. In general, the heavier seedweight classes had the highest seedling emergence over all depths of planting and, as expected, seedling emergence decreased with increased depth of planting. Seedling emergence of yellow‐flowered alfalfa can be increased by selecting for high seed weight.