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Field experiment was conducted to determine effects of nitrogen & plant density on growth & bulb yield of onion. Treatments comprised factorial combination of 6 levels of nitrogen and 4 plant densities. A 6x4 factorial experiment was laid out in RCBD with 3 replications.Effects of nitrogen & plant density were assessed by analyzing data on plant growth & bulb yield of onion.Results showed increasing level of nitrogen resulted significantly on plant height,leaf number per plant,LAI,shoot dry weight, highest total bulb yield,higher bulb diameter, maximum average bulb weight, marketable yield & maturity date.But,increasing nitrogen levels had no effect on number of leaves per plant in the 1st 2 days after transplanting, bulb dry mater content, total soluble solid & harvest index. Plant density had highly significant effect on plant height,leaf area index,bulb yield,average bulb weight, marketable yield & maturity date.Bulb yield was maximized at 150 kg N ha-1 & using plant density of 400,000 plants ha-1.But the partial budget analysis indicated that 100 kg N ha-1 with 400,000 plants ha- 1 yielded promising marginal rate of return of 201.32%.

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The author recieved his BSc Degree in Plant Production & Dry Land Farming from Awassa College of Agriculture in 2005. Then after,he worked for 3 years as an Agronomist Expert at Alamata, Southern Tigray.He recieved his MSc in Horticulture from Hawassa University in 2009 & is currently working as a lecturer at Dilla University,Ethiopia.

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