Onion (Allium cepa L.) is considered as one of the most important vegetable crops produced on large scale in Ethiopia and also occupies economically important place among vegetables in the country [1]. The area under onion is increasing from time to time mainly due to its high profitability per unit area and ease of production, and the increases in small scale irrigation areas. Ethiopia has a great potential to produce onion throughout the year both for local consumption and export [2]. Onion is grown primarily for its bulb which is used for flavoring the local stew, ‘wet’ which is considerably important in the daily diet, mostly used as seasonings or as vegetables in stews. It is one of the richest sources of flavonoid in the human diet and flavonoid consumption has been associated with a reduced risk of cancer, heart disease and diabetes. In addition it is known for anti-bacterial, antiviral, anti-allergenic and antil-inflammatory potential [3].
The crop is produced both under rainfed in the ‘Meher’ season and under irrigation in the dry season. In many areas of the country, the dry season cropping (under irrigation) constitutes much of the area under onion production. Despite the increase in cultivated areas, the productivity of onion is much lower than other African countries and the world average. The low productivity could be attributed to the limited availability of quality seeds and associated production technologies used [1]. According to [4], for private farmers’ holdings in ‘Meher’ season 2012/2013, the total area coverage by onion crop in the country was 21,865.4 ha, with total production of 219,188.6t with average productivity of 10.02t ha-1. This is very low yield compared to the world average of 19.7t ha-1 [5]. The low yield level could be due to low soil fertility, salinity effect and inappropriate cultural practice [6].
The Shebelle river banks and sinks along the Gode district are one of the most suitable areas for the production of onion. Recently onion growers in the study area started producing onion for home consumption as well as cash crop by irrigation. Farmers in the study area are mostly engaged in livestock production and few have recently started sedentary agriculture. Thus, productivity of most of the crops, including onion, is low due to poor agronomic and management practices. Moreover, lack of improved varieties and seed, absence of recommended N fertilizer rate and plant spacing are the pertinent problems of the study area. Currently the nationally recommended fertilizer rate of 100 kg DAP ha-1 (46 kg P2O5 ha-1) and split application of 150 kg Urea ha-1 are used along with 10cm plant spacing for onion production with no consideration of soil types [1,7]. However, farmers in Gode area have no experience of applying the nationally recommended fertilizer rate and plant spacing rather they randomly practice undetermined fertilizer rate and plant spacing. Therefoe, the objective of the study was to determine the effect of N fertilizer rates and intra-row spacing on bulb yield characters of onion.