Response of Common Bean (Pharsalus vulgaris L.) Cultivars to Combined Application of Rhizobium and NP Fertilizer at Melkassa, Central Ethiopia

Soil fertility is one of the factors limiting the production of common bean in Ethiopia. Thus, field experiment was conducted to assess the effect of Rhizobium and NP fertilizers combination on nodulation, growth, yield components and yield of common bean cultivars and economically beneficial combination of NP and inoculants for each cultivar. The experiment was conducted at Melkassa Agricultural Research Center under rain fed conditions during the main cropping season. The experiment plot was laid at split plot design in three replications. Seven common bean cultivars (sub-plot factor) with five levels of NP fertilizer combined with inoculant (main-plot factor) (full recommended rate of NP fertilizer or 46 kg ha-1 of P2O5 and 41 kg ha-1of N alone, Rhizobium with 23 kg ha-1 of P2O5 and 20.5 kg ha-1of N, Rhizobium with 11.5 kg ha-1 of P2O5 and 10.25 kg ha-1of N, Rhizobium alone, and control) used as treatments. The main effects of combination of NP with inoculant significantly influenced, nodule number, nodule color, plant height and number of primary branches. All inoculated treatments recorded highest nodulation parameters over uninoculated. The combination of 23 kg ha-1 of P2O5 and 20.5 kg ha-1 of N with inoculant recorded highest nodule number (17.14) per plant. Among the cultivars, Nassir was best for nodulation parameters. The interaction of combined application of NP fertilizer with inoculant and cultivars had significant effect pods per plant, 100 seed weight and grain yield. Analysis of variance for net benefits significantly affected due to common bean cultivars, combine application of NP fertilizer with inoculant and interaction of cultivars and combined application of NP fertilizer. The Economic analysis indicated that full recommended rate of NP fertilizer had economical advantage for only cultivar Awash-1. Among the cultivars Batu, DRK and Nassir recorded the highest marginal rate of return due to inoculation relative to other tested combination. Finally, Study conclude that, rhizobium strain (EAL 429) is more effective than that of indigenous soil Rhizobium population. Cultivar Nassir seemed to be more responsive to infection by inoculated strain EAL 429. However, the results presented here need to be further evaluated for sound recommendation.f