Perennial and annual pasture species in the control of Silybum marianum

Abstract

Experiments begun in 1958 near Boorowa in the south-west slopes of New South Wales, have demonstrated the superiority of the perennials Hunter River lucerne (Medicago sativa L.) and Phalaris tuberosa L. over the annuals, Wimmera ryegrass (Lolium rigidum Gaud.) and subterranean clover (Trifolium subterraneum L.) in reducing establishment and growth of the annual thistle, Silybum marianum (L.) Gaertn. At one harvest (1959) the fresh weights of thistles varied from 0 in lucerne and 1 or 2 tons an acre in Phalaris to about 11 tons an acre in the annual plots. At another harvest (1960) the dry weight of thistles varied from about 0.2 cwt an acre in lucerne and Phalaris to about 5 cwt an acre in ryegrass plots. In the period of the experiment (mid 1958 to early 1967) there was an 85 per cent reduction in the numbers of apparently viable seeds of Silybum present in the soil of plots sown to lucerne and Phalaris.