Effect of NPS Rates and Row Spacing on Production of Faba Bean (Viciafaba L.) at High-land of North Shewa Zone of Oromia, Ethiopia

Plant density and poor soil fertility are among the major factors that limit faba bean production in the study areas. Therefore, a field experiment was conducted to determine the optimum NPS (nitrogen, phosphate, and sulfur with the ratio of 19% N, 38% P2O5, and 7% S) rate and appropriate inter-row spacing for faba bean production in the highlands of the north Shewa zone of Oromia, Ethiopia. Factorial combination of four rates of NPS (0, 50, 100, 150 kg ha-1) and four inter-row spacing (30, 40, 50, 60cm) were laid out in a Randomized Compete Block Design (RCBD) with three replications. The result of the study indicated that the soil required amending with organic fertilizers to enhance soil fertility. Both the main and the interaction effects of NPS and inter-row spacing significantly influenced the faba bean phenological and growth parameters. However, NPS had more profound effects in enhancing the growth response of the crop than inter-row spacing. Increasing the rate of NPS from nil to 100 kg ha-1 resulted in a 30% increase in grain yield, with no further increases noted beyond this level. However, the result revealed that increased inter-row spacing from 30cm to 60cm decreased grain yield. Decreasing inter-row spacing implies high plant density, which consequently correlates with high yield. The total yield per unit area depends not only on the performance of individual plants but also on the density of plants per unit area, as confirmed in this study. The maximum net benefit of 91,639.5 ETB ha-1 with an acceptable marginal rate of return 486.3% was obtained from the application of 100 kg ha-1 NPS rate and 30 cm inter-row spacing. Thus, this rate and inter-row spacing are suggested for faba bean production in the north shewa zone.