Enhancing sesame (Sesamum indicum L.) seed yield and yield components through optmized NPSB fertilizer rates and variety selection in Buno Bedele, southwest Ethiopia

Sesame is Ethiopia’s second most important agricultural export after coffee, generating over $449 million annually. A field experiment was conducted during the 2021 cropping season to evaluate the response of sesame varieties to varying rates of NPSB (nitrogen, phosphorus, sulfur, and boron) fertilizer in Bedele and Dabo Hana districts, Southwest Ethiopia. The study used a randomized complete block design with a 4 × 3 factorial arrangement and three replications. Treatments included four NPSB fertilizer rates (0, 50, 100, and 150 kg ha⁻¹) and three sesame varieties (Chalasa, Obsa, and Dicho). Data were collected on phenological, growth, and yield-related parameters. Results showed that both NPSB fertilizer rates and variety significantly ( p < 0.05) affected flowering, branching, capsule number, biomass yield, and seed yield. The Dicho and Obsa varieties significantly ( p < 0.05) outperformed Chalasa in seed yield. Applying 100 kg ha⁻¹ of NPSB fertilizer to the Dicho variety resulted in the highest biomass and seed yields, while Obsa produced the highest oil yield at 150 kg ha⁻¹. Economic analysis revealed the highest net benefit ratio and return from 100 kg ha⁻¹ NPSB in both districts. In conclusion, applying 100–150 kg ha⁻¹ of NPSB fertilizer combined with Dicho or Obsa varieties can maximize sesame yields in the study area and similar agro-ecologies.