Relationships between growth and competitiveness of four annual weeds.
Abstract
Competitive relationships among Amaranthus retroflexus, Chenopodium album, Echinochloa crus-galli and Solanum nodiflorum were investigated under field conditions at Davis in 1983 by replacement series experiments. 6 complete series, matching each sp. with all other spp., yielded a consistent hierarchy of aggressiveness in the order E. crus-galli > A. retroflexus > C. album > S. nodiflorum. The primary interaction was competition for similar resources. Growth analysis performed simultaneously with the competition experiments showed that RGR did not vary significantly among the 4 spp. Canopy area index was 0.640, 0.761, 0.203 and 0.862 for A. retroflexus, C. album, E. crus-galli and S. nodiflorum, resp.; root:shoot ratio and leaf area ratio were 18.09, 13.89, 30.88 and 13.80, resp., and 147.0, 155.9, 128.4 and 241.3, resp. RGR was poorly correlated with agressiveness of the 4 spp.; the best-fitting linear regression relating competitiveness to growth ability described aggressiveness as a function of plant weight, unit leaf rate and leaf area ratio.