Azospirillum affects Eh and potential denitrification in a soil

The effect of inoculation withAzospirillum brasilense (strain 7001) on soil Eh under anaerobic conditions (N₂ flux) was examined during 144 h at 26°C and 230 h at 18°C. The Eh values of the control (not inoculated) soil decreased to approximately 80 or 140 mV in both cases, whereas after 24 h of anaerobic incubation, the Eh of theAzospirillum-inoculated soil remained at higher values. After 144 and 230 h of anaerobic incubation, the denitrifying activity (measured in anaerobiosis with excess of e^- acceptor and donor) in the inoculated soil was seven and three times lower respectively, than in the non-inoculated soil. This indicates thatAzospirillum may affect the soil Eh and consequently any highly Eh-dependent microbial activity, such as denitrification.