Co-inoculation with Mesorhizobium ciceri and Azotobacter chroococcum for improving growth, nodulation and yield of chickpea (Cicer arietinum L.)

Rhizobia have the exceptional ability to form nodules on roots or stems of leguminous plants. Free living diazotrophs promote the rhizobial efficiency by altering root architecture providing more niches for nodulation and thus enhance the N2-fixing ability of legumes. Field experiment was conducted to assess the co-inoculation potential of symbiotic i.e. Mesorhizobium ciceri and non-symbiotic diazotrophs i.e. Azotobacter chroococcum on the yield of chickpea. Chickpea seeds (cv. Bittle-98) were inoculated with peat-based inocula and sown following randomized complete block design with three replications. Two levels of nitrogen i.e. 30 (recommended) and 15 kg ha(-1) were applied as urea while P was applied at 60 kg ha(-1) to all the treatments as single super phosphate. Results revealed that introduction of A. chroococcum had positive impact on chickpea with and without rhizobial inoculation and the effect was more prominent when applied in combination as compared to non-inoculated control at low nitrogen level. It was observed that inoculation with M. ciceri or A. chroococcum produced significant increase in biomass and grain yield but the response was more pronounced with co-inoculation i.e. 3456 and 1772 kg ha(-1), respectively, as compared to control (2903 and 1489 kg ha(-1), respectively) at 15 kg N ha(-1). Higher nodule number plant-1 and nodular mass was observed with co-inoculation (42 and 0.252 g plant-1). Percent N and P content in chickpea plant were higher in the co-inoculated treatments (1.683 and 0.283%) than that of their respective controls. Similar trend was observed in grains except the rhizobial inoculation alone which produced higher N content (3.62%) than coinoculation (3.59%). Percent N and available P in soil were also higher in the inoculated treatments. The results imply that co-inoculation with Mesorhizobium and Azotobacter could be a useful approach for improving growth, nodulation and yield of chickpea by reducing dependence on chemical fertilizers and saving similar to 50% of recommended N fertilizer. However, more comprehensive and detailed studies in different ecological zones on the farmer's field for cost effective crop production should be carried out to confirm this approach.