To evaluate the effect of bio-fertilizers on physiological traits in soybean under water deficit condition, a
greenhouse experiment was conducted in 2011, at faculty of Agriculture, Tarbiat Modares University,
using a factorial design based on RCBD with three replications. The experimental treatments were
different irrigation regimes including non-stress (40% water depletion), moderate stress (60% water
depletion) and severe stress (80% water depletion) and four methods for application of mixed of
Azotobacter and Azosperilium on plant or seed. Results showed that the highest yield and yield
components were observed in non-stress and spraying of bacteria on leaf + seed inoculation conditions.
The highest catalase enzyme activity was observed in moderate stress and seed inoculation + spraying of
bacteria on leaf condition. In addition, the highest proline content was showed in severe stress and nonbacterial
inoculation and was three times more than the minimum treatment. The results generally
indicated that using bio-fertilizer in moderate stress can reduce the destructive effects of stress and
decrease of yield, but severe stress led to increase of cost of production and could not effect on increasing
of yield significantly.