Competition among pasture plants. II. The influence of density on flowering and seed production in annual pasture plants.

Abstract

Inflorescence and seed production were studied in swards of varying 5 density of two annual Mediterranean pasture plants, Trifolium subterraneum L. and Lolium rigidum Gaud., each in pure culture. While the maximum level of dry matter production, achieved at moderate densities, was maintained at all higher densities, seed production showed a peak at moderate densities and thereafter a progressive decline. The greatest number of inflorescences was produced at densities exceeding those of peak seed production. Although the most widely spaced plants had the greatest numbers of inflorescences and seeds per plant, they had smaller seeds and fewer seeds per inflorescence than did substantially denser swards, apparently owing to intense intra-plant (inter-inflorescence) competition at the widest spacings. It is suggested that the results can be explained in terms of the changing competitive relationships between and within the plants of the sward at the times of initiation of flower primordia, of floral development, and of seed production. Dense swards give most of the attributes needed in the use of these plants for grazing purposes; for seed multiplication swards of moderate densities give the highest yields of seed per unit area.