Effect of Rhizobium and PGPR Inoculation in Mungbean on Productivity and Soil Properties in Mungbean-Wheat Sequence

Abstract

A field experiment was carried out at Pantnagar in Mollisols during 2017-18 to study the performance of mungbean (Vigna radiata L.) as influenced by seed inoculation with Rhizobium sp. and plant growth promoting rhizobacteria (PGPR), alone and in combination. Their residual contribution was assessed on productivity of succeeding wheat (Triticum aestivum L.) at three N levels and soil properties. Rhizobium sp. alone gave significant increases in nodule number by 24.6 per cent, nodule dry weight by 19.3 per cent and plant dry weight by 16.3 per cent over the uninoculated control at 45 DAS. The PGPR alone gave significant increases in nodule number by 13.7 per cent, nodule dry weight by 16.1 per cent and plant dry weight by 9.6 per cent over the uninoculated control at 45 DAS. However, combined use of Rhizobium sp. and PGPR resulted in significantly more nodule number by 44.5 per cent, nodule dry weight by 23.9 per cent and plant dry weight by 40.4 per cent over the uninoculated control. Conjoint use of Rhizobium sp. and PGPR also resulted in 8.6 and 11.7 per cent increases in mungbean grain and straw yields, respectively over control. It also significantly improved available N, P and K in soil, by 18.8, 55.8 and 17.1 per cent, respectively over the uninoculated control at the harvest. Irrespective of N levels, Rhizobium sp. and PGPR inoculation in mungbean resulted in 3.85 and 3.87 t ha-1 wheat grain yield as compared to 3.65 t ha-1 with uninoculated mungbean crop. Their combined application further increased the wheat grain and straw yields by about 9.1 per cent over the uninoculated mungbean. Different inoculation treatments also significantly improved the various yield attributes of wheat. Dual inoculation of Rhizobium sp. and PGPR in mungbean also significantly increased soil available N by 15.3 and 16.9 per cent and soil available P by 26.8 and 49.0 per cent, at 45 and 75 DAS of wheat over the uninoculated mungbean, respectively. This treatment also recorded 28.0 and 24.4 per cent more dehydrogenase activity, 8.6 and 11.5 per cent more microbial biomass carbon, 21.1 and 25.1 per cent more acid phosphatase and 18.1 and 25.3 per cent more alkaline phosphatase activity in soil at 45 and 75 DAS over the uninoculated control, respectively. Increasing levels of N significantly increased the wheat grain and straw yields, available N and P, microbial biomass carbon and dehydrogenase, acid and alkaline phosphatase activities in soil at 45 and 75 DAS.