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SEED PHYSIOLOGY, PRODUCTION & TECHNOLOGY

White Clover Seed Production

III. Cultivar Differences under Contrasting Management Practices

^a Bolsista da Capes, Dep. de Plantas Forrageiras e Agrometeorologia, Faculdade de Agronomia, UFRGS, CP. 776, 91.501-970, Porto Alegre, Brazil
^b National Forage Seed Production Research Center, USDA-ARS, 3450 SW Campus Way, Corvallis, OR 97331 USA

steinerj{at}ucs.orst.edu

Information is needed to determine the optimal combinations of agronomic practices for white clover (Trifolium repens L.) seed production in humid temperate marine climatic conditions. Effects on seed yield were determined for two stand ages (first and second seed year of production), six cultivars varying in leaf size (ladino large-leaf type: Canopy, California Ladino, Osceola, and Regal; and intermediate leaf-type: Louisiana S-1 and White Dutch), grown with and without spring herbage removal, and with and without supplemental irrigation. The experiment was arranged in a modified split-split-split-plot design with four replications. First year seed was harvested in 1997, and first and second year seed was harvested in 1998. Intermediate-leaf size cultivars reached initial bud and flower stages earlier than large-leaf types, but there were no differences between the two leaf types at the time of seed harvest. The number of flowers produced early in the reproductive period for nonirrigated plants was highly correlated with seed yield. Supplemental irrigation delayed flower maturity, but herbage removal did not. First seed year yields were greater than second seed year yields for all cultivars except Osceola, which had similar yields both seed years. Supplemental irrigation only increased seed yields of Canopy. In first seed year stands, White Dutch was the only cultivar that did not recover lost seed yields due to herbage removal when supplemental irrigation was applied. Herbage removal and supplemental irrigation treatments generally did not increase white clover seed yields under the conditions of this experiment, so maximal yields were generally achieved with minimal management inputs.

Abbreviations: GDD, growing degree days • TAGP, total aboveground phytomass