Growth and Bulb Yield of Onion ( Allium cepa L .) in Response to Plant Density and Variety in Jimma, South Western Ethiopia

In appropriate use of plant spacing and lack of evaluation of improved varieties across agro ecologies are the predominant agronomic practices that reduce the productivity of onion. The present study therefore, has been designed to investigate the influence of variety, intra-row spacing and their possible interaction on growth and yield of onion. The study was conducted under irrigation during the year 2016/2017 at Jimma University College of Agriculture and Veterinary Medicine, on experimental site of horticultural crops. Four onion varieties (Adama Red, Nafis, Melkam and Nasik Red) and three intra-row spacing (7,10 and 13 cm) with inter-row spacing of 20 cm. The experiment was designed in RCBD with three replications. The results of the study showed that both variety and intra-row spacing had a significant effect (P˂0.05) on all parameters, except for the leaf diameter which was only affected by intra-row spacing. Leaf number per plant was significantly affected by interaction of variety and intra-row spacing. The highest leaf number (13.9) obtained from variety Nafis with intra-row spacing of 13 cm. In general, leaf number per plant, leaf length, plant height and leaf diameter were higher at wider intra-row spacing (13 cm). Nafis variety was superior in terms of leaf number per plant (13.9), bulb diameter (5.67 cm), average bulb weight (74.50 g), marketable yield (36.26 t ha-1) and total bulb yield (36.28 t ha-1). Onion plant grown at closer intra-row spacing (7 cm) showed very promising result for average bulb weight, marketable yield and total tuber yield. Moreover, the closest intra-row spacing (7 cm) gave higher marketable and total bulb yield than the wider intra-row spacing. Thus, growers in the study area can be benefited from closer intra-row spacing, however, it is paramount important to test the feasibility of the other closest intra-row spacing e.g., 6 cm and 4 cm.