Sward growth of monocultures and binary mixtures of phalaris, lucerne, white clover and subterranean clover under two defoliation regimes

Abstract

Sirosa phalaris, WL5 15 lucerne, Haifa white clover and Seaton Park subterranean clover were grown in monocultures and binary mixtures on a cracking clay soil and cut at 4- and 8-week intervals over 3 growing seasons at Scone, New South Wales (32�S.). The plots were given supplementary irrigation between mid April and November to prevent water deficits. The deep-rooted perennials dominated mixtures under infrequent cutting, with cumulative dry matter yields for the growing season reaching 11 t/ha for lucerne-based mixtures. Frequent defoliation increased the contribution of the clovers in mixtures, and mixtures and monocultures containing clovers were more productive than other plots in winter, 1986. Frequent defoliation reduced the vigour and density of lucerne, resulting in balanced mixtures with phalaris and subterranean clover in the third year. Only lucerne plots contributed large amounts of dry matter yield (up to 4 t/ha) between December and April. Regeneration of subterranean clover from seedlings, and white clover from seedlings or stolons, was better in clover-only plots than in mixtures with phalaris. The growth of mixtures in response to mean daily air temperature in spring could be divided into 2 distinct patterns, with growth peaking at about 15�C for determinate (annual or dormant) mixtures, and at about 18�C for lucerne mixtures and pure white clover. In autumn, growth patterns were determined by the method of regeneration (i.e. by seedings or dormant crowns).