A Comparison of Seed Quality and Seedling Vigor in Birdsfoot Trefoil

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Abstract
Seed quality, seedling vigor and field establishment were estimated in seed lots of three forage legumes, birdsfoot trefoil (Lotus corniculatus L.), alfalfa (Medicago sativa L.) and red clover (Trefolium pratense L.) in 1979 and in birdsfoot trefoil in 1980. Birdsfoot trefoil showed greater variability for germination than either red clover or alfalfa. Among 49 seed lots of birdsfoot trefoil tested in 2 years, 18 had less than 75% germination with a range of germination from 19 to 100%. Seed lots with poor germination generally had poor seedling vigor as measured by electrical conductivity, speed of germination and rate of seedling elongation. The maximal values of seedling vigor in birdsfoot trefoil were comparable to minimal values observed in alfalfa, except for electrical conductivity measurements which were similar between species. Quality measurements which were significantly correlated (p=0.01) with field establishment of birdsfoot trefoil (1980 data) were germination (r2=.66), electrical conductivity (r2=.59), speed of germination (r2=.66) and rate of seedling elongation (r2=.25). Seed weight was not significantly correlated with field establishment. Electrical conductivity had the highest correlation with establishment when measured after 24 hours soaking, compared to 1 and 6 hours soaking periods.In seed lots of birdsfoot trefoil with over 75% germination, field establishment was still significantly different between lots. Some of this variability can be accounted for by differences among the cuitivars Leo, Empire, Maitland and Viking. For example, the cultivar Leo had superior speed of germination and field establishment compared to Empire. Seed size was not a reliable indicator of seedling vigor between seed lots of the same variety. Electrical conductivity was not reliable for comparisons among cultivars. Germination, speed of germination, seed size, electrical conductivity, and other unidentified factors contributed to successful field establishment, but the most limiting factor varied among seed lots. Thus, the prediction of a seed lot's field establishment based on only one measure of seed quality is tenuous.