Influence of rhizobacteria on the performance of urdbean (Vigna mungo)-rhizobium symbiosis

Field and laboratory experiments were conducted to examine the influence of plant growth promoting Rhizobacteria (PGPR) on the competitive ability and performance of inoculated Rhizobium sp. on symbiosis in urdbean. Field study was conducted during kharif 2004–05 in mollisol at Pantnagar Research Farm. The soil was sandy loam of pH 7.3 having 0.61% of organic C and 160.0, 16.0 and 296.0 kg/ha available N, P and K, respectively. Treatments consisting of four PGPR (PUK-171, PUK-46B6, PUK-315 and KB-133), alone and with Rhizobium sp. and control, were tested in RBD. The test crop variety was PU-35. All PGPR stimulated Rhizobium growth in in vitro conditions. Rhizobium sp. alone inoculation significantly increased the nodulation, plant dry matter, grain yield and N, P accumulation in urdbean and residual N and P in soil after crop harvesting. Different PGPR alone inoculation also improved the root nodulation, grain yield by 24.2 to 54.2%, straw yield by 18.0 to 45.5%, N and P uptake and residual N and P over control. The different PGPR also gave increase of 4.5 to 29.6% in grain yield and 13.5 to 30.3% in straw yield over Rhizobium sp. alone inoculation. Dual inoculation of different PGPR with Rizobium sp. further improved the various growth parameters and yield; however, significant increase in grain and straw yield over Rhizobium sp. was recorded only with Rhizobium sp.+PUK-46B6 and Rhizobium sp.+KB-133. Both these treatments also gave significantly more number and dry weight of nodule at 30 and 45 DAS, N and P uptake by grain and straw and residual P in soil.