Effect of NPS Fertilizer Rate and Intra Row Spacing on Growth and Yield of Common Bean (Phaseolus vulgaris L.) at Metu, South western Ethiopia

The production of common bean has been increasing in Ethiopia because of its high importance as a source of protein, and foreign exchange earnings. Low available phosphorus, total nitrogen and sulphur are the major yield limiting factors for common bean production in the study area. The use of optimum intra row spacing is also one of the agronomic practices to increase its productivity. Thus, an experiment was conducted at Metu in 2019 (July-October), to evaluate the effect of NPS fertilizer rates and intra row spacing on growth and yield of common bean and to identify economically feasible combination of the two factors. The experiment was laid down in randomized complete block design in factorial arrangement with three replications. Hence, factorial combinations of four NPS fertilizer rates (0, 50, 100 and 150 kg ha1 ) and three levels of intra row spacing (5cm, 10cm and 15cm) were tested. Result showed that NPS rates had highly significant effect on number of days to 50% flowering, which showed the highest value (48.00) for application of 150 kg NPS ha1 , Similarly, NPS rates and intra row spacing had highly significant effect on the number of days to 90% physiological maturity, plant height, pod length, number of pods per plant, hundred seed weight, total above ground dry biomass yield, and harvest index. The highest number of days required to physiological maturity (101.56 and 97.17), number of pods per plant (24.53) and (17.52), pod length (11.43cm) and (10.83cm), hundred seed weight (55.24g and 49.19g), harvest index (0.314 and 0.287) were recorded for 150kg NPS and 15cm intra row spacing respectively. The highest leaf area (2751.39cm 2 ) was recorded for the interaction of 150kg NPS ha1 and 15cm plant spacing. Maximum plant height with the respective values of 77.83cm 59.35cm was recorded for 150kg NPS ha1 and 5cm intra row spacing. The highest above ground dry biomass yield (11449.1 and 11052.1 kg ha1 ) was recorded for 150kg NPS ha-1 and 15cm intra-row spacing, respectively, while maximum grain yield (4041.67) was recorded for the interaction of 150 kg NPS ha-1 and 5cm intra row spacing. The Longest plant (77.83cm) and (59.35cm) was obtained at 150kg NPS ha1 and 5cm intra row spacing respectively, the highest above ground dry biomass yield (11449.1 kg ha1 ) and (11052.1) was recorded at 150kg NPS ha1 and 5cm plant spacing respectively, number of branches, number of nodules, and number of seeds per pod were high significantly and significantly affected by NPS rates and intra row spacing respectively. The highest number of branches (3.11) and (2.35) was recorded at 150kg NPS ha1 and the next result recorded for 10cm and 15cm plant spacing respectively. The highest number of seeds per pod (7.88 and 7.63) was recorded for 150 kg NPS ha1 and 15cm intra row spacing respectively, the highest number of nodules (77.44 and 63.89) was recorded at 150kg NPS ha1 and 5cm intra row spacing respectively. The highest agronomic efficiency (56.1) was recorded for 50kg NPS ha1 . The economic analysis also indicated that the highest net return (46, 148 ETB ha1 ) was obtained from 5cm intra row spacing with application of NPS at the rate of 150 kg ha1 with marginal rate of return of 861.2%. Based on the results of this study, it can be tentatively concluded that application of 150 kg NPS rate of 150 kg ha1 combined with 5cm intra row spacing would be appropriate for common bean production in the study area.