Weeds in grain-lupins. 1. The effect of weeds on grain-lupin yields

Abstract

Narrow-leafed lupins (Lupinus angustifolius) were grown at two densities in weed free conditions and with different levels of either capeweed (Arctotheca calendula) or annual ryegrass (Lolium rigidum). Capeweed that germinated six weeks before the lupins prevented grain production. Germinated with the lupins, 30 capeweed plants m-2 reduced grain yields by 20 per cent compared with 10 capeweed plants m-2, which was not significantly different from the weed free control. Thirty capeweed plants m-2 that germinated six weeks after the lupins did not reduce grain yields. Ryegrass reduced grain yields by 70 per cent when it germinated six weeks before the lupins. Germinated with the lupins, 90 ryegrass plants m-2 reduced grain yields by 47 per cent compared with the weed free control. Ninety ryegrass plants m-2 that germinated six weeks after the lupins did not reduce grain yield.