Evaluation of Co-inoculation of Bradyrhizobium japonicum and Phosphate Solubilizing Pseudomonas spp. Effect on Soybean (Glycine max L. Merr.) in Assossa Area

An experiment was conducted at Assossa Agricultural Research Center (AARC) station during 2008 cropping season in order to study the effects of co-inoculation of Bradyrhizobium japonicum (TAL-378 and TAL-379) and phosphate-solubilizing bacteria (PSB) (Pseudomonas spp.), and conventional farmers’ fertilizer level (combined and individual application of 46N kg ha-1 and 46 P2O5 kg ha-1) on nodulation, seed yield and yield components of soybean (Glycine max L. (Merr.)). Analyses of variance indicated that most of the parameters measured were significantly (P>0.05) affected by the treatments. Accordingly, dual inoculation with TAL-378 and PSB significantly increased plant height at harvest, number of nodules per plant, nodule volume per plant, nodule fresh weight per plant, and shoot height at late flowering and early pod setting compared to the other treatments. Similarly, co-inoculation with TAL-378 and PSB, and dual fertilization of nitrogen (N) and phosphorus (P) fertilizers significantly increased number of pods per plant, number of seeds per pod per plant and seed yield ha-1 compared to the other treatments. Analysis of plant tissue also indicated that dual inoculation of TAL-379 and PSB yielded the highest total N whereas the lowest was recorded for the negative control. Likewise, dual inoculation with TAL-378 and PSB and the positive control gave the highest plant P compared to all other treatments. The data revealed that, there was no significant difference (P>0.05) in days required for emergence, flower bearing and maturity, number of seeds per pod, 300 seeds weight and root length among the investigated treatments. Thus, the dual inoculation of TAL-378 and PSB is recommended to achieve maximum seed yield of soybean in Assossa area.