Two field experiments were carried out during 1999 and 2000 seasons at the Experimental Farm, Fac. of Agric. Moshtohor to study the effect of dual inoculation with Bradyrhizobium japonicum and vesicular arbuscular mycorrhizae( Glomus mosseae ) in presence of either super phosphate or rock phosphate on the modulation N2-fixation, mycorrhizal root infection percentage, macro and micro-nutrients
content, growth and yield of soybean plants. Results of this study showed that inoculation with B. iaponicum and VA-mycorrhizae increased N2-ase activity , mycorrhizal Key words: Bradyrhizobium, Mycorrhizae, soybean, Inoculation, Rock phosphate,
Superphosphate, Growth and yield infection percentage, plant growth and macro nutrients (N,p and K) and micro-nutrients (Fe, Zn and Cu) contents of the plants compared to the application of each inoculum singularly. Application of rock phosphate rather than super-phosphate increased the above mentioned parameters.Super -phosphate
captivation gave lower records of nodulation , N2-ase activity, mycorrhizal root infection compared to rock phosphate application. Yield and yield components of soybean plants
were significantly increased in treatments inoculated with either Bradyrhizobium or VAM fungus as well as the combination of them and fertilized with rock phosphate compared to that inoculated and fertilized with super-phosphate. The highest records of protein and oil yield were observed in the treatment of dual inoculation and fertilization
with rock phosphate. Therefore, rock phosphate using combined with dual
inoculation by Bradyrhizobium and Endomyconhizae can be recommended as an
alternative for super-phosphate to reduce the production costs of soybean.