Plant Growth, Bulb Yield and Quality of Two Onion (Allium cepa L.) Cultivars as Affected by Storage Conditions of Three Set Sizes

Abstract

The objective of this research was to investigate the effect of storage conditions of different onion set sizes on plant growth, yield and quality of the bulb crop. Treatments comprised two cultivars (Kamlin and Saggai), two storage conditions (refrigeration at 2-4 ○c and room temperature around 32○c) and three set sizes (large-bulb diameter 2.2-2.7 cm, medium 1.6-2.1cm and small 1-1.5 cm). Experimental design was split-split plot design with three replications. Cultivars were in the main plots, set sizes in the sub-plots and storage conditions in the sub-sub plots. Sets were stored in the cold storage for 8 weeks; the other set lot was kept at room temperature in the shade for the same period. Results indicated that refrigerated storage of sets resulted in significantly higher plant fresh and dry weights than room storage. Large set size gave significantly more vegetative growth than medium and small set size. Response of cultivars was not consistent in both seasons for vegetative growth. Set size and set storage temperature did not significantly affect average bulb weight, total and marketable yields, bulb shape index and dry matter. Yet, refrigerated storage of sets resulted in an increase in average bulb weight ranging from 5 % to 13 % and in total yield
from 9 % to 18 %. Large sets resulted in increase in total yield ranged from 21 % to 23 %. The proportion of marketable yield to the total yield ranged from 67 % to 90 % in Kamlin and from 51 % to 84 % in Saggai cultivar.
Regarding bulb quality, cultivars were not significantly consistent in their effect on bulb diameter and shape index in both seasons. Bulb dry matter was significantly higher in Kamlin than Saggai. Pre-mature bolting was negligible, if not at all, in the first season. Refrigerated storage of planted sets did not significantly affect bulb attributes in the first season. In the second season, however, it significantly affected bulb diameter, splitting and bolting such that it was more promotive than room temperature storage. Set size significantly affected bulb splitting and bolting such that large sets gave the highest percentage (undesirable) and the small size sets gave the lowest (desirable). It is concluded that refrigerated storage of onion sets significantly enhanced early vegetative growth, increased total and marketable yields, but also increased bulb splitting and bolting