Yield and profitability responses of potato to nitrogen and blended fertiliser rates in the Bule district of Ethiopia

Low potato yields in Ethiopia, particularly in the Bule District, present a significant challenge to food security and the livelihoods of farmers, primarily due to poor soil fertility. There is a critical lack of localised data on the effectiveness of nitrogen (N) and blended 19% N, 38% P2O5, 7% S, and 0.1% B (NPSB) fertilisers in this specific district. To address this gap, a field study was conducted to assess how varying levels of nitrogen (0, 46, 69, 92 kg ha⁻¹) and NPSB (0, 146.25, 195, 243.75 kg ha⁻¹) fertilisers influence potato yield and profitability. The experiment employed a factorial combination in a randomised complete block design with three replications. The results demonstrated significant impacts on above-ground biomass (AGBY), marketable tuber yield (MTY), and total tuber yield (TTY). The highest TTY (42.55 t ha⁻¹) was observed with the maximum application of 92 kg N ha⁻¹ combined with 243.75 kg NPSB ha⁻¹, while the lowest yield (19.51 t ha⁻¹) was recorded in the control plot without fertiliser. Based on these findings, the combination of 92 kg N ha⁻¹ and 243.75 kg NPSB ha⁻¹ is economically optimal as an effective management practice for potato farming in the Bule District. This combination produced MTY 37.7 t ha⁻¹ and TY 42.55 t ha⁻¹ (p < 0.001 for main effects), with a net benefit of $8,987.66 ha⁻¹ and MRR 1,295.5%. The marginal rate of return of 1,295.5% further underscores the economic viability and potential for substantial profit margins when adopting this fertiliser application strategy.