Abstract:
Low available phosphorus, total nitrogen, lack of adequate information on the use of Rhizobium inoculants and nitrogen-phosphorus-sulphure blended fertlizer are the major yield limiting factors for common bean production in the study area. Thus, the experiment was conducted at Bolosso Bombe District in 2016 (July-October), to evaluate the effect of Blended NPS fertilizer rates and Rhizobium inoculation on the yield components and yield of common bean varieties; and to identify economically appropriate combination of blended NPS fertilizer rate and Rhizobium inoculation that give maximum yield of major common bean varieties. Factors studied were three common bean varieties (Red Wolaita, Hawassa Dume, Nasir), three levels of blended NPS fertilizer rate (0, 100, 200 kg ha-1) and two levels of Rhizobium inoculation (with and without). Randomized complete block design in factorial arrangement with three replication was used. Result showed varieties had significant differences on days to 50% flowering, days to 90% physiological maturity and plant height. The highest number of days to 50% flowering (42.89) and days to 90% physiological maturity (82.56) were recorded for variety Red Wolaita. Similarly, NPS rates and Rhizobium inoculation had significant effect on days to 50% flowering and days to 90% physiological maturity. Significantly higher number of days to 50% flowering (42.59) was recorded from Rhizobium inoculation. The highest number of days to 90% physiological maturity (90.83) was recorded at blended NPS rate (200 kg ha-1). There was significant interaction effect of NPS rates with varieties on grain yield and effective nodules. Where, the highest effective nodules per plant (19.32) and grain yield (2373 kg ha-1) were recorded from NPS rate 100 kg ha-1 of for variety Nasir. The combined application of Rhizobium inoculation with NPS rates and varieties had significant effect on number of total nodules per plant and seeds per pod. Where, the highest number of total nodules per plant (68.53) and seeds per pod (7.5) were recorded from Rhizobium inoculation with NPS rate 100 kg ha-1and for variety Nasir. The economic analysis also indicated that the highest net return of 18695.3 ETB ha-1 was obtained from Rhizobium inoculation for variety Nasir and application of NPS rate of 100 kg ha-1with marginal rate of return of 772.3%. Based on the results of this study, it can be tentatively concluded that Rhizobium inoculation with application of NPS rate of 100 kg ha-1 found to be appropriate for common bean variety Nasir as well as for other varieties, where variety Nasir was superior of production in the study area
