Competitive growth of capeweed (Arctotheca calendula) and some annual pasture species

Abstract

A comparison of the relative growth rates (RGR) of plants of capeweed (Arctotheca calendula), subterranean clover (Trifolium subterraneum) and annual ryegrass (Lolium rigidum) under high soil fertility conditions showed capeweed to have a higher RGR in the early weeks of growth, offsetting the effect of smaller seed size. However, when grown in mixed swards with the clover, under conditions of high NPK and water availability, capeweed did not readily suppress clover growth. If the capeweed and clover began growth together, clover growth was reduced by associated capeweed only after twelve weeks of growth, and then only slightly. If the capeweed was established four weeks before the clover there was a marked reduction of clover growth at the harvest eight weeks after the clover was sown. The results suggest that 'smothering' of clover by capeweed through competition for light is unlikely in grazed pastures in southern Australia.