Symbiotic efficiency vis-à-vis chickpea performance as affected by seed inoculation with Mesorhizobium, phosphorus-solubilizing bacteria, and phosphorus application

Biofertilizers are important for sustainability of agriculture and have the potential to reduce the environmental costs of nitrogen (N) and phosphorus (P) fertilizers in modern intensive farming practices. Field experiments were conducted on two promising strains of P-solubilizing bacteria (PSB) viz. RB-1 (Pseudomonas argentinensis) and RB-2 (Bacillus aryabhattai) identified in the lab studies, in conjunction with N-fixing Mesorhizobium, for improving symbiotic efficiency, growth and productivity of irrigated desi chickpea. An experiment comprised of four biofertilizer seed inoculation treatments (uninoculated control, Mesorhizobium, Mesorhizobium + RB-1 and Mesorhizobium + RB-2), and four P levels (0, 15, 20 and 25 kg P2O5 ha−1) was conducted. Dual inoculation with Mesorhizobium + RB-1 and Mesorhizobium + RB-2 proved more effective in increasing nodulation in chickpea at lower dose of P of 15 and 20 kg ha−1 as compared with Mesorhizobium + 25 kg P ha−1. Chickpea with Mesorhizobium + RB-1 recorded similar leghaemoglobin content in nodules and chlorophyll content in leaves as achieved with Mesorhizobium + RB-2; however, both of these attributes improved significantly over Mesorhizobium alone. Improved plant growth with both Mesorhizobium and PSB resulted in significant grain yield increase up to 7% as compared with Mesorhizobium alone. Investing additional US $0.74 ha−1 on PSB to current growers' practice of single inoculation with Mesorhizobium resulted in additional net returns increase of US $53-71 ha−1. Therefore, biofertilizers that promote N-fixation and P-solubilization need to be adopted in conjunction with each other in chickpea to reduce chemical fertilizer usage and improve profitability.