Interactions between azospirillum and va mycorrhiza and their effects on growth and nutrition of maize and ryegrass

Interactions between the N₂-fixing bacterium Azospirillum brasilense and the mycorrhizal fungus Glomus mosseae were studied in relation to their effects on the growth and nutrition of Zea mays (C₄) and Lolium perenne (C₃) plants. Although roots from plants inoculated with Azospirillum exhibited C₂H₂ reduction activity no significant effect of inoculation on N concentration in the plant shoots was found. With non-mycorrhizal plants, inoculation with Azospirillum resulted in increased dry matter production at the first harvest compared to the effect achieved by supplying N as fertilizer, but this trend was reversed at the last harvest. However, with mycorrhizal maize plants, Azospirillum, which stimulated the development of VA mycorrhiza, was still effective in improving plant growth and nutrient uptake at the last harvest. Azospirillum and N behaved similarly in enhancing the growth and nutrition of mycorrhizal maize. The dual inoculation of maize by Azospirillum and Glomus produced plants of a similar size, N content, and a higher P content, than those supplied with N and P.