Influence of integrated phosphorus supply and plant growth promoting rhizobacteria on growth, nodulation, yield and nutrient uptake in Phaseolus vulgaris
To guarantee a sufficient phosphorus supply for plants, a rapid and permanent mobilization of phosphorus from the labile phosphorus fractions is necessary, because phosphorus concentrations in soil solution are generally low. Several plant growth-promoting rhizobacteria (PGPR) have shown potential to enhance phosphorus solublization and nodulation of legumes when co-inoculated with Rhizobium. This investigation was undertaken to assess the feasibility and compatibility of two mineral phosphorus fertilizers; diammonium phosphate (DAP), triple super phosphate (TSP), poultry manure (PM) and two PGPR strains on the growth, nodulation, yield, nutrient uptake and protein content of common bean (Phaseolus vulgaris) under deficient phosphorus supply. Integrated application of mineral phosphorus (P), PM and PGPR significantly increased shoot height, shoot fresh weight, shoot dry weight and leaf chlorophyll content by 67, 160, 51 and 106%, respectively, while increase in root length, root fresh weight and root dry weight was 79, 161, and 187%, respectively, over unfertilized control without PGPR application. Integrated use of different P sources and PGPR also increased number of nodules per plant, nodule fresh weight and nodule dry weight by 158, 107 and 168% over the control. Treatment with PGPR significantly increased number of pods per plant and grain yield by 224 and 96%, respectively over the control. Co-inoculation with Bradyrhizobium sp. strain MN-S and Agrobacterium sp. strain Ca-18 demonstrated two-fold increase in the proportion of nitrogen (N) and P uptake as well as protein content of the common bean grain was increases by 48%. Therefore, application of PGPR with low P fertilizer rates and PM could be a viable supplementary strategy for maximum benefits in terms of cost of production and sustaining productivity.
Key words: Phaseolus vulgaris L., plant growth promoting rhizobacteria (PGPR), nodulation, yield, phosphorus deficiency, protein.