Influence of different CO2 levels on the growth, competition and herbicide sensitivity of some important weeds in maize (Zea mays L.)

The aim of this study was to investigate the effect of different CO2 levels on the growth, competition and herbicide sensitivities of Sorghum halepense, Echinochloa cruss-galli, Amaranthus blitoides and Solanum nigrum in maize (Zea mays L.). The effect of two different CO2 level on the emergence of weed was investigated as the first step of the studies. This step was followed by studies concerning the growth of weeds and maize under ambient and elevated CO2 conditions each with and without concurrence with maize/weeds. The last step of the study was to compare the herbicide sensitivities of the weeds under tested CO2 conditions. Results showed that elevated CO2 resulted with higher emergence rates in the case of some weeds. Maize growth was influenced by CO2 levels depending on the competitive conditions, so that under elevated CO2 conditions maize plants produced less biomass without competition while the biomass of maize was higher in the case of competition with weeds. Weed competition reduced in some experiments weed biomass significantly under ambient CO2 conditions, while no biomass reduction occurred under elevated CO2 conditions in most cases. Also weed response to elevated CO2 was variable depending on competitive conditions. Weed growth was generally improved by high CO2 under competitive conditions with weeds. Results of herbicide sensitivity experiments showed that elevated CO2 caused in general lower herbicide effects. The results of these studies showed that the increase in the future atmospheric CO2 level would influence the competition between maize and weeds, as well as the success of weed control measurements.