Influence of Nitrogen Rates on Growth, Yield and Quality of Onion (Allium cepa L.) Varieties in West Dembia District, North Western Ethiopia

Abstract

 Onion (Allium cepa L.) is highly important vegetable in the daily diets of Ethiopians as flavoring
of dishes, sources of important carbohydrate, protein and several nutrient elements. However, its
productivity is low mainly due to low soil fertility, improper fertilizer application and limited use
of improved onion varieties. Hence, a field experiment was conducted under irrigation to
evaluate the effects of nitrogen rates on growth, yield, and quality of onion varieties. The
treatment consisted of a factorial combination of six levels of nitrogen rates (0, 46, 69, 92, 115
and 138 kg N ha-1) and two improved onion varieties (Adamared and Bombayred), which were
laid out in a randomized complete block design in three replications. The collected data were
analyzed using SAS software. The analysis of variance showed that the main effect of nitrogen
rates on all tested parameters was significant while the main effects of varieties had significant
effect on all parameters except plat height, number of leaves and unmarketable yield. Adamared
variety gave higher marketable bulb yield (15.56 t ha-1) than Bombayred (13.89 t ha-1). The
application of 138 kg N ha-1 gave the highest marketable bulb yield (19.23 t ha-1) and the
maximum net benefit (253965 birr ha-1) with acceptable marginal rate of return (2804%).
However, application of 138 kg N ha-1 reduced quality parameters of onion bulbs. It increased
neck diameter, decreased dry matter content and total soluble solids. It also caused the highest
percent rots, sprouts and weight losses of bulbs during the eight month storage life. It can be
concluded that application of 138 kg N ha-1 for Adamared variety can be used for better
productivity in the study area.