Effects of elevated carbon dioxide on arbuscular mycorrhizal fungi activities and soil microbial properties in soybean (Glycine max L. Merrill) rhizosphere

Arbuscular mycorrhizal fungi (AMF) help in promoting plant growth and mediating key belowground processes, however, little is known about AMF responses to the continuous increase in the atmospheric carbon dioxide (CO2). This has led to considerable interest in its impacts on AMF and belowground processes in recent years. The study investigated the effect of elevated CO2 on AMF sporulation and root colonization and soil properties in the roots of soybean. The pot experiment consisted of two levels of CO2 (ambient; 350 ppm and elevated; 550 ppm) and three soybean cultivars (TGx 1440-1E, TGx 1448-2F and TGx 1480-2F) conducted in open top chambers, laid out in randomised complete block design, replicated thrice. The results showed that elevated CO2 increased the AMF spore density and root colonization of the soybean cultivars. Elevated CO2 increased the microbial biomass carbon (34.2% - 45.4%), microbial biomass nitrogen (44.6% - 54.9%), soil nitrogen (30.3 – 50.6%), available phosphorus (20.8 – 45.7%) in the rhizosphere of the soybean cultivars compared to the ambient CO2. These could have resulted in higher dry biomass, pod number, seed number 100-seed weight and seed yield observed under elevated CO2. From the results of this study, increased atmospheric CO2 regulates AMF activities, microbial properties and improve soybean performance. Thus, this study may help to better understand the responses of AMF and belowground process with increasing atmospheric CO2.