This study reports the effectiveness of some selected rhizobium strains in enhancing nitrogen fixation and nutrient uptake in Vicia faba L. Multi-location field experiments were conducted for two years (2016 and 2017) using a split-plot in randomized complete block design. Treatments comprised six rhizobium strains as the main plot factor and three varieties of Vicia faba as the sub-plot factor. Non-inoculated plants with or without N fertilizer served as +N and −N controls, respectively. Peat carrier-based inoculant of each strain was applied at the rate of 10 g kg−1 seed. Data on nodulation were taken at the late-flowering stage, whereas nitrogen and phosphorus concentrations in plant parts were analyzed at physiological maturity. The total nitrogen difference method was employed to quantify nitrogen fixation. Location x rhizobium strain x variety interaction had a significant effect on nodule dry weight plant−1. Rhizobium strains significantly enhanced nodulation, nitrogen fixation, nutrient uptake and soil nitrogen balance. Inoculation with NSFBR-12 and NSFBR-15 resulted in the highest nitrogen fixed, nutrient uptake and soil nitrogen balance. Vicia faba inoculated with the two top performing strains, NSFBR-12 and NSFBR-15 fixed respectively 87.7% and 85.5% of the total nitrogen uptake. Non-inoculated plants fulfilled proportionately more of the total nitrogen uptake through nitrogen derived from the soil rather than fixed nitrogen. Soil available phosphorus and pH had appreciable influences on nitrogen and phosphorus uptake of inoculated Vicia faba. Inoculation with competitive and effective rhizobium strains can improve soil nitrogen balance, nitrogen fixation and nutrient uptake of Vicia faba.
NITROGEN FIXATION IN THE ROOT NODULES OF VICIA FABA L. IN RELATION TO THE ASSIMILATION OF CARBON. II. THE DARK FIXATION OF CARBON DIOXIDE
