EFFECT OF RHIZOBIUM INOCULATION, PHOSPHORUS AND GYPSUM APPLICATION ON NODULATION, YIELD COMPONENTS AND YIELD OF COMMON BEAN (Phaseolus vulgaris L.) AT FADIS, EASTERN ETHIOPIA

Ensuring food security is one of the greatest challenges facing the world scientific community to feed the ever-increasing human population in a sustainable way. The low soil fertility is one of the major constraints which limit crop production in sub-Saharan African countries including Ethiopia. The major soil related constraints in the study area are strongly alkaline condition, high soil pH, low soil OM, low available P and medium total N. Therefore, a field experiment was conducted at Fadis Agricultural Research Center under rainfed condition during 2016 main growing season to evaluate the effect of phosphorus (P), gypsum (G) and Rhizobium inoculation (R) on nodulation, yield and yield components of common bean. The experiment comprised of three factors with four levels of P (0, 23, 46 and 69 kg of P2O5 Kg ha-1), two levels of G (with and without G) and three levels of R (uninoculated, HURIPV-16 and CIAT-899). The treatments were arranged factorialy in Randamized Complete Block Design (RCBD) with three replications. Common bean-Awash Melka variety was used as a test crop. Analysis of the results revealed that the main effect of P and G as well as their two-way interaction (P×G) significantly affected nodule parameters, phenological charaterstics, yield and yield components of common bean. However, the main effect of R and its interaction with other factors did not influence any of the studied parameters. The highest mean total number of nodule per plant (24.59) was obtained in response to application of 69 kg P2O5 ha-1 whereas the highest mean effective number of nodule per plant (24.24) and nodule volume per plant (1.882 gm) were obtained in response to application of 69 and 46 kg P2O5 ha-1 with G application which resulted in 61.88%, 146.59% and 80.44% increased over the control check, respectively. The highest mean days to 50% flowering (51.56days) was obtained at 23 kg P2O5 ha-1. The highest mean days to 90% physiological maturity (100.1days) was recorded from the P and G control check. The highest mean plant height (36.58 cm), number of branches per plant (6.078), number of pods per plant (28.78),grain yield (2402 kg ha-1), and harvest index (34.99%) were obtained in response to application of 46 kg P2O5 ha-1 with G whereas hundred seed weight (20.27 gm) was obtained under combined application of 69 kg P2O5 ha-1 with G and the highest mean above ground dry biomass (6394.06 kg ha-1) was obtained from G application alone. The economic analysis revealed that the highest net return (50,320ETB ha-1) with a marginal rate of return of 1214.88% was obtained from combined application of 46 kg P2O5 ha-1 with G. Hence, it can be tentatively concluded that combined application of 46 kg P2O5 ha-1 plus gypsum is found to be appropriate combination. However, this research needs to be evaluated over locations and seasons to give a conclusive recommendation for common bean production in the study area.