Comparative growth of wheat, barley, and annual ryegrass (Lolium rigidum) in monoculture and mixture

The growth and development of wheat, barley, and annual ryegrass (Lolium rigidum Gaud.) were studied in monoculture and in additive mixtures at two sites of contrasting climate and soil type in New South Wales. Although smaller, annual ryegrass paralleled the behaviour of the two cereals in monoculture in all respects. The phenological development of all three species was more rapid at the wheatbelt site (Forbes) than on the coastal plain (Camden); yield loss was also greater at Forbes. The early growth rate of barley was greater than that of wheat or ryegrass at both sites. As a result, barley was more able to suppress ryegrass in mixtures and to maintain its yield than wheat. Sensitivity analysis of a growth simulation model suggested that the early rate of leaf production was likely to be influential in determining the magnitude of biomass reduction at anthesis; relative phenological development and height growth dynamics appeared to have little effect.