SPRING DEFOLIATION OF WHITE CLOVER SEED CROPS .2. POTENTIAL HARVESTABLE SEED YIELD AND SEED YIELD COMPONENTS OF CONTRASTING WHITE CLOVER CULTIVARS

The effects of different spring defoliation managements on potential h arvestable seed yield and seed yield components of three contrasting w hite clover cultivars were assessed. The small-leaved cv. S 1 84 produ ced more but smaller inflorescences than the large-leaved cv. Olwen an d Menna, a medium-leaved cultivar. Cultivar Olwen, however, produced m ore ripe and brown (nearly ripe) inflorescences with more florets, see ds per floret and a higher seed yield per ten inflorescences than the other cultivars. Potential harvestable seed yield and individual seed yield components were only influenced by defoliation after bud emergen ce, as defoliation before bud emergence had no effect on seed yield co mponents. Defoliation after bud emergence had a similar effect on all cultivars: the number of ripe inflorescences was unaffected by defolia tion but the number of brown and therefore harvestable (ripe + brown) inflorescences was highest following defoliation three weeks after bud emergence. Florets per inflorescence, seed per floret, 1000 seed weig ht, seed yield per ten inflorescences and potential harvestable seed y ield were not influenced by defoliation after bud emergence. Season ha d a significant effect on seed yield components and influenced the eff ect of defoliation treatments, emphasizing the importance of climate i n white clover seed production. The results are discussed in relation to the spring defoliation of white clover seed crops, harvesting techn iques and the provision of guidelines for optimizing seed yield.