Effect of N and NPSB Fertilizer Rates on Growth, Yield and Yield Components of tef (Eragrostis tef (Zucc.)Trotter) Varieties in Gechi District, Southwestern Ethiopia

Background: Tef [Eragrostis tef (Zucc) Trotter] serves as a crucial staple meal for around 57.2 million individuals in Ethiopia, or over 64% of the nation's entire population, and is a significant source of sustenance and income. However, its growth and yield are mainly constrained by inappropriate soil fertility management and lack of site- and variety-specific fertilizer recommendations. Therefore, a field experiment was conducted during the 2020 main cropping season under rainfed conditions on a farmer's field in the Gechi district, southwestern Ethiopia. The study aimed to assess the impact of varying rates of N + NPSB fertilizer on the growth, yield, and yield components of tef varieties, as well as to determine the economically optimal amounts of N + NPSB fertilizer for enhanced yields of tef varieties in the testing environment. Methods: The treatment was laid out in a 3*6 factorial RCBD consisting of tef varieties and N + NPSB fertilizer rates with three replications. SAS versions 9.3 was used to record growth, yield, and yield component data and perform an analysis of variance (ANOVA). Results: Except for days to 50% flowering (DF), days to 90% physiological maturity (DPM), and harvest index (HI), the results indicated that the main and interaction effects of variety and fertilizer rates were significant (p < 0.05) for all the variables examined. The highest grain yield (2565.4 kg ha ^-1 ), thousand seed weight (0.30 g), and harvest index (30.64%) were recorded from the Kora variety under an application rate of 34.5 kg N + 200 kg NPSB fertilizer ha ^-1 . Based on partial budget analysis, the combination of Kora variety and 34.5 kg N + 200 kg NPSB fertilizer ha⁻¹ ^{gave the highest net benefit of 93,447.45 Birr ha⁻¹ with a marginal rate of return (MRR) of 1082.4% Birr ha⁻¹, which could be considered as profitable for the farmers in the study area.The Kora variety exhibited the maximum agronomic efficiency, applying 23 kg N + 150 kg NPSB fertilizer ha⁻¹. Conclusions: The study suggests that farmers in the study area can use 34.5 kg N + 200 kg NPSB and Kora variety. However, since the data is obtained from only one season and location, it will be worth repeating the experiment under field conditions across different seasons and locations to draw sound conclusions and recommendations.}