Evaluation of Alternative, Fixed, and Conventional Furrow Irrigation on the Yield of Onion, Jimma Zone South Western Oromia

Efficient use of limited irrigation water is essential for sustaining crop productivity in water-scarce regions of Ethiopia. Onion (Allium cepa L.), a high-value horticultural crop, is widely cultivated under small-scale irrigation systems, yet its production is often constrained by inefficient water management. This study evaluated the effects of three furrow irrigation methods — Alternative Furrow Irrigation (AFI), Fixed Furrow Irrigation (FFI), and Conventional Furrow Irrigation (CFI) — combined with three irrigation levels (50%, 70%, and 100% ETc) on the growth, yield, and water use efficiency of onion in the Jimma Zone of southwestern Oromia. A randomized complete block design with three replications was used over two cropping seasons. The results demonstrated that irrigation method and irrigation level had significant impacts on key agronomic traits, bulb yield components, and water use efficiencies. The highest marketable bulb yields were obtained from CFI100% ETc (9.3 t/ha) and CFI70% ETc, followed closely by AFI100% ETc (8.7 t/ha), which produced statistically comparable yields while using 50% less irrigation water. Deficit irrigation under AFI showed remarkable water-saving benefits without substantial yield penalties. AFI50% ETc and AFI70% ETc produced moderate yields but achieved the highest irrigation water use efficiency (IWUE) and crop water use efficiency (CWUE), reaching 74.37 kg/mm and 55.73 kg/m<sup>3</sup>, respectively. In contrast, FFI50% ETc produced the lowest yield performance due to prolonged water stress in non-irrigated furrows. Overall, AFI100% ETc provided the best balance between high yield and efficient water use, demonstrating its suitability for water-limited environments. The findings suggest that AFI, particularly at full irrigation, can serve as a sustainable alternative to conventional furrow irrigation, helping farmers optimize water productivity without compromising crop output. The study recommends wider adoption of AFI100% ETc in regions facing irrigation water shortages.