Effect of Bradyrhizobium Inoculation on Nodulation, Biomass Production and Yield of Mungbean

Legumes are considered to be an important component of subsistence cropping systems because of their ability to form nodules in symbiotic process with Rhizobium bacteria, which convert atmospheric nitrogen (N2) into assimilable form of ammonia, to add substantial amount of organic matter to the soil and to grow better than many other crops with low inputs under harsh climatic and edaphic conditions. The global concern about sustainable agricultural systems further highlights the significance of legumes, which offer a renewable source of energy through biological nitrogen fixation (BNF). Annual global BNF has been estimated at around 175 million tons of N of which about 79% is accounted for terrestrial fixation1. Mungbean (Vigna radiata L Wilczek) is one of the most important conventional pulses grown in Bangladesh. It plays an important role in improving the soil fertility by fixing atmospheric nitrogen into available form with the help of rhizobial species present in the nodules of its roots and also important in human diet. However, under agro-ecological conditions of Bangladesh, the nodulation of mungbean is poor, which is one of the major causes of its low yield. Rhizobium inoculation in mungbean increased number of pods and seed yield2-3. Thakur and Panwar4 and Solaiman et al.5 found an increase in seed yield of mungbean with Rhizobium seed inoculation. There is common notion that legume crop does not need nitrogenous fertilization for their proper growth. Nodulation, biomass production and yield of mungbean by different mungbean cultivars may vary considerably due to variation in genotype, soil and environmental factors influencing the process of symbiosis between the macroand the microsymbionts. Among the various factors, soil N or added N fertilizer and the type of legumes/crop cultivars, are considered to be the major factors influencing nodulation, N2-fixation and biomass production by the legumes. Bangladesh Agricultural Research Institute (BARI) and Bangladesh Institute of Nuclear Agriculture (BINA) have recently developed and released a number of high yielding varieties of mungbean for use by the farmers of the country. Nodulation, biomass production and seed yield by these varieties are worth to be compared to make a good selection for inclusion into rice-wheat cropping system.