Effect of planting space on bulb yield and yield components of onion (Allium cepa L.) in Gamo Zone, South Ethiopia

The experiment was conducted at Arba Minch Zuria and Mirab Abaya districts during 2020 and 2021 cropping seasons to determine the best planting pattern for bulb yield and yield components of onion and to indentify optimum planting space for onion production. It consisted of 12 treatments (20x5, 30x5, 40x5, 20x10, 30x10, 40x10cm, 30x15x5, 40x20x5, 50x25x5, 30x15x10, 40x20x10 and 50x25x10cm inter and intra row spacing) and arranged in Randomized Complete Block Design with three replications. The results revealed that plant height, bulb diameter, marketable and unmarketable bulb yield were significantly affected by planting space. The highest marketable bulb yield was obtained from 30x15*5cm without significant variation with 20x5cm, 30x15*10cm and 50x25*5cm spacing at both locations. The lowest marketable bulb yield was recorded from planting space of 40x10cm and 30x5cm at two locations. From this study, it was also observed that the use of single and double row at 20x5cm (inter and intra row, respectively) and 30x15x5cm planting space, respectively resulted better onion bulb yield in study areas. Based on partial budget analysis, growing of onion under double row planting pattern at the planting space of 30x15x5cm gave maximum net benefit and marginal rate of return at both locations. Therefore, double row planting pattern at 30x15x5cm planting space could be optimum to obtain better onion bulb yield and highest net benefit and recommended for small-scale onion growers in the study areas and other areas with similar agro-ecological conditions.