EFFECTS OF ELEVATED CO₂ ON GROWTH, YIELD, AND PHENOLOGY OF SOYBEAN

Abstract

Increasing atmospheric carbon dioxide (CO₂) concentrations as a consequence of global climate change may affect the physiological responses, growth, and productivity of soybean (Glycine max L.). However, plant responses to elevated CO₂ remain variable, highlighting the need for further research to understand the responses of different soybean varieties. This study aimed to evaluate the effects of elevated CO₂ concentrations above the canopy on the phenology, growth, and yield of three soybean varieties, namely Dena 1, Deja 1, and Grobogan. The experiment employed a strip-plot design within a randomized complete block design (RCBD), comprising two CO₂ treatments, without and with CO₂ enrichment, and three soybean varieties. The observed variables included plant phenology, growing degree days (GDD), growth, and yield components. The results showed that CO₂ treatment had no significant effects on plant height, leaf number, or seed moisture content, but had highly significant effects on root fresh weight, root dry weight, and 1,000-seed weight. Soybean variety significantly affected shoot fresh weight and shoot dry weight, whereas the interaction between CO₂ treatment and variety had no significant effect on any of the observed variables. These results indicate that soybean growth and yield responses to elevated CO₂ varied among the measured parameters. Under the conditions of this study, elevated CO₂ concentrations did not consistently improve soybean growth and yield.