Response of legumes to co-inoculation with nodule bacteria and plant growth promoting rhizobacteria

Plant growth-promoting rhizobacteria (PGPR) of the genus Pseudomonas have been reported to increase the yield of nonleguminous plants. Inoculation with Pseudomonas has been found by some authors to improve nodulation of legumes. This work examined the response of various legumes to a combined inoculation with Pseudomonas and nodule bacteria in pot experiments under field conditions in gray forest soil of Russia’s southern Moscow Region. Co-inoculation increased the weight of pea and soybean grain, alfalfa and clover shoots in comparison with nodule bacteria alone. Addition of mixed bacterial cultures promoted macroand micronutrient uptake by legumes from soil. Pseudomonas improved N nutrition of pea and soybean by increasing amounts of N derived from air, soil and N-labelled starter fertilizer. Nodulation and N2 fixation of soybean inoculated with Pseudomonas and nodule bacteria were promoted by addition of P fertilizer in a greenhouse pot experiment. The beneficial effect of combined inoculation resulted from the promotion of symbiotic N2 fixation and nutrient uptake by leguminous plants without any considerable change in the chemical composition of produce. PGPR-based inoculants can be used to increase the yield of leguminous crops without microfertilizers added.