COMPARATIVE GROWTH OF WHEAT, BARLEY, AND ANNUAL RYEGRASS (LOLIUM-RIGIDUM) IN MONOCULTURE AND MIXTURE

The growth and development of wheat, barley, and annual ryegrass (Loli um 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) tha n 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 ry egrass at both sites. As a result, barley was more able to suppress ry egrass in mixtures and to maintain its yield than wheat. Sensitivity a nalysis of a growth simulation model suggested that the early rate of leaf production was likely to be influential in determining the magnit ude of biomass reduction at anthesis; relative phenological developmen t and height growth dynamics appeared to have little effect.