The influence of seed pre-treatment with Rhizobium and plant growth promoting rhizobacteria on nodulation and nitrogen fertilizer optimization in soybean (Glycine max L.)

In order to study the influence of soybean (Glycine max L.) seed pre-treatment with Rhizobium japanicum and plant growth promoting rhizobacteria (PGPR) on nodulation and nitrogen fertilizer optimization, a spilt plot experiment based on randomized complete block design with three replications was conducted in 2011 at the research farm of the Islamic Azad University, Ardabil Branch. Factors were: nitrogen fertilizer rates at four levels (0, 25, 50 and 75 kg urea/ha) in the main plot and soybean seed pre-treatment with Rhizobium and plant growth promoting rhizobacteria (PGPR) in four levels containing of without seed inoculation as control, inoculation seed with Rhizobium japanicum, Azotobacter chroococcum strain5, Azosprilium lipoferum strain OF. The results showed that with increasing the amount of fertilizer, fertilizer use efficiency was reduced. Maximum number (16) and dry weight (16 mg) of nodules was obtained in seed inoculation with Rhizobium japanicum along with application of 50 kg urea/ha and minimum of these traits were observed in without of urea fertilizer application and seed inoculation. So, the highest plant height (117.22 cm), number of pod per plant (54.72), grain hundred weight (28.26 g) and grain yield per area (267 g/m2) was obtained in Rhizobium japanicum whit application of 75 kg urea/ha. At the level of 75 kg urea/ha fertilizer, inoculation with Azosprilium, Azotobacter and Rhizobium bacteria increased seed yield (14.4, 21.4 and 40.6 percent, respectively) compared to non-inoculation. Based on the results, it was concluded that application of 75 kg urea/ha in seed inoculation with Rhizobium can be recommended for profitable soybean production in the study area.