Seedling Growth and Nodulation of Arrowleaf, Crimson, and Subterranean Clovers1

Abstract

AbstractCool‐season annual clovers (Trifolium spp.) are overseeded in warm‐season perennial grasses to extend the grazing season and to incorporate symbiotically fixed N in the pasture system. Overseeding grass sods with clover often fails because of grass competition and unfavorable climatic conditions during the establishment period. Seed size and its effect on seedling vigor was determined on three cultivars of arrowleaf (Trifolium vesiculosum Savi.) clover, crimson (Trifolium incarnatum L.) clover, and subterranean (Trifolium subterraneum L.) clover. Each fall for 3 years clover seedlings were excavated 3 and 7 weeks after planting in 1976 and 1977, and 5 and 13 weeks in 1978. Nodules, leaves, and weight per seedling, percent protein, and total dry matter production were determined.The species seed weight ratio for arrowleaf:crimson:subterranean was 1:2.9:6.8 with minor differences between cultivars within species. Subterranean clover means were always highest for nodules, leaves, and weight per seedling except for the 13‐week sampling in 1978. Arrowleaf clover means were always lowest with crimson being intermediate. The most dramatic species difference was for seedling weight with subterranean seedlings three to four times and crimson seedlings two to three times heavier than arrowleaf seedlings. Seedling weight differences between species decreased with time and did not affect total forage production for the season. There was a high correlation of seed weight with nodule and leaf number and at the earlier samplings for seedling weight. Percent protein and yield were not significantly correlated with seed weight. Ranking of the three clover species for nodules, leaves, and weight per seedling in this study was identical to that for seed weight. Thus, subterranean clovers should be the least difficult to establish and most competitive, followed by crimson and then arrowleaf clover.