Competitive effects of sorghum cultivars and densities on weed suppression

Field studies were conducted in southern Queensland to determine the impact of sorghum cultivars and crop densities on weed suppression and sorghum yield loss due to weeds. Japanese millet (Echinochloa esculenta (A.Braun) H.Scholtz) was used to mimic barnyard grass (Echinochloa spp.). Results showed that differences in competitive ability of the cultivars were consistent over the two years, with MR Goldrush and Bonus MR being the most competitive cultivars, and 86G87 the least competitive. Sorghum density also had a significant effect on the crop’s ability to compete with millet, with the strongest millet suppression at the highest density of 7.5 plants m. Millet caused significant yield loss, up to 34% in comparison with weed-free plots. These results indicate that sorghum competition against Japanese millet can be improved by choosing competitive cultivars and the use of higher crop densities. Improved sorghum competition provides a non-chemical option for integrated weed management.