RESPONSE OF SOYBEAN TO PHOSPHORUS FERTILIZER UNDER THE EFFECT OF SOME PLANT GROWTH PROMOTING RHIZOBACTERIA

Abstract

Two-field experiments were conducted at Nubaria Agricultural Research Station, ARC. in summer seasons of 2006 and 2007; consecutively to study the response of soybean cultivar Giza 111, inoculated with Bradyrhizobium japonicum, to different rates of phosphorus fertilizer in the presence of Bacillus megatherium, Bacillus polymyxa or a mixture of both to give a highlight on the role of these microorganisms in increasing enzymatic activity in soil after 75 days of sowing and in increasing soybean yield and N, P and K seeds contents under the calcareous soil conditions in Nubaria. With respect to nitrogenase activity of nodules and rhizosphere and nodules weight, data show that the inoculation increased significantly nitrogenase activity (N2- ase) of nodules in both seasons, while it gave a significant increase in nodules weight of the 2nd season. N2- ase of rhizosphere soil increased significantly in the 1st season as a result of inoculation. Regarding the effect of inoculation and phosphorus fertilizer on dehydrogenase activity (DHA) of rhizosphere soil, results indicated that inoculation with both bacteria led to a significant increase in DHA only in the 2nd season. Results showed also that inoculation of soybean seeds with a mixture of both bacteria plus 30 kg P2O5/fed gave the highest significant grain yield, 100-grain weight, protein yield and N, P, and K contents of soybean seeds in both tested seasons over uninoculated treatments. Consequently, results revealed that inoculation of soybean seeds with B. polymyxa combined with 30 kg P2O5/fed produced significantly the highest oil yield as compared to uninoculated treatment. It can be concluded that the improvement of soybean yield and its quality could be achieved by the application of 30 kg P2O5/fed together with inoculation of seeds with (Bradyrhizobium japonicum and a mixture of B. megatherium, B. polymyxa) under calcareous soil conditions.