Yield and Yield Components of Onion as Influenced by Intra-Row Spacing and Nitrogen Fertilizer Levels in Rift Valley, Ethiopia

Background and Objectives: Farmers currently employ nationally approved fertilizer rates and plant spacing when growing onions, but knowledge of plant population density and fertilizer rates that may produce the best bulb production for different cultivars and locations is limited. As a result, gardeners frequently use nonspecific plant population densities for various cultivars, resulting in sub-optimal bulb yields. Materials and Methods: A field experiment was conducted in 2019 from August to December to study the effects of intra-row plant spacing and levels of nitrogen on yield and quality of onion (Allium cepa L.) variety Nafis under irrigation. Results: The main effect of intra-row spacing on stand count and both nitrogen levels and intra-row spacing on plant height and the number of leaves per plant was observed. The interaction of nitrogen level and intra-row distance affected days to maturity, leaf length, leaf diameter, bulb diameter, mean bulb weight, marketable and unmarketable bulb yield, and all bulb size categories. Increased intra-row spacing to 10.5 cm and N rate of 82 kg ha-1 increased marketable and total bulb yield by approximately 3.14 and 3.21 t ha-1, respectively, spacing and decreased unmarketable bulb yield by 1.38 t ha-1. Conclusion: The use of 82 kg ha-1 N at the intra-row spacing of 10.5 cm was optimum for bulb production of onions. 82 kg ha-1 N at 10.5 cm intra-row spacing resulted in the highest net benefit.