Interactive effect of Rhizobium strains and P on soybean yield, nitrogen fixation and soil fertility

Pot studies under natural conditions were undertaken to determine the effect of various exotic Bradyrhizobium japonicum strains viz., TAL 377, 379, 102 used alone or in mixture with and without phosphorus on soybean growth, yield and nitrogen fixation parameters. Surface sterilized soybean seeds (NARC-4 var.) coated with Rhizobium strains were sown in earthen pots. Phosphorus (P) was applied as single super phosphate (SSP) at the time of sowing in the soil. Nitrogenase activity, pink bacteriodal tissue volume and specific nitrogenase activity was determined at flowering stage. These parameters were relatively higher when mixed rhizobial strains were applied in combination with P. However, efficiency of different rhizobial strains for specific nitrogenase activity and other parameters was TAL102>TAL379>TAL377 either alone or in combination with P. Application of Rhizobium strain and P also increased the growth and yield of soybean and also improved soil fertility and NPK uptake by plant tissues. It is concluded that increase in soybean yield can be achieved by applying Rhizobium mixed culture with phosphorus, which also improved soil fertility for sustainable agriculture system.