Yield and Yield Attributes Responses of Soybean (Glycine max L. Merrill) to Elevated CO2 and Arbuscular Mycorrhizal Fungi Inoculation in the Humid Transitory Rainforest

Abstract

Variations in yield components and grain yield of arbuscular mycorrhizal fungi (AMF) inoculated soybean varieties (Glycine max L. Merrill) grown in CO₂ enriched environment in the humid rainforest were tested.  A screen house trial was established with soybean varieties (‘TGx 1448-2E’, ‘TGx 1440-1E’ and ‘TGx 1740-2F’), AMF inoculation (with and without) and CO₂ enrichment (350±50 ppm and 550±50 ppm) in open top chamber, arranged in completely randomised design, replicated three times. A field trial was also conducted; the treatments were arranged in a split-split plot configuration fitted into randomised complete block design. In the main plot the variant was CO₂ enrichment, the sub-plot consisted of AMF inoculation (with and without), while the sub-sub plot consisted of soybean varieties, replicated three times. Both trials had significantly higher grain yield at elevated CO₂ than ambient. This could be attributed to improved yield attributes, more spore count and root colonisation. In both trials, inoculated soybean had significantly higher dry pod weight than un-inoculated, which could suggest the increased grain yield observed on the field. AMF inoculated soybean varieties outperformed un-inoculated in both CO₂ enriched and ambient concentrations. AMF inoculated soybean variety ‘TGx 1740-2F’ is most preferable in CO₂ enriched environment, while variety ‘TGx 1448-2E’ had the most stable grain yield in all growth environments.