Abstract
An experiment was carried out between October 2007 and March 2008 at the permanent site of the University of Jos (08°53'E, 09°57'N; 1,159 m above mean sea level) to investigate the effect of day length extension on the yield of onion bulb (Allium cepa L.). Two varieties of onion ('Violet de Galmi' and 'Red Creole') were combined with normal, additional 2, 4 and 6 hours after darkness in a completely randomized design with four replications. The results showed that the mean weight of bulb, size of bulb, diameter of bulb, length of bulb and the mean number of rings per bulb increased with increasing day length extension, ranging from 119.74 g to 223.23 g; 15.39 cm - 25.04 cm; 5.69 cm - 8.60 cm; 4.31 cm - 5.76 cm and 6.13 - 10.25 rings respectively. The variety ''Violet de Galmi'' exceeded the variety ''Red Creole'' in all parameters except the mean bulb length, where it was 4.97 cm as against 5.03 cm in the variety ''Red Creole''. There was significant day length extension and variety interaction on the mean bulb-weight, bulb-size, bulb-diameter, bulb-length and the number of rings per bulb. The variety ''Red Creole'' was observed to be more affected by longer day length extension than the variety ''Violet de Galmi'' in the Jos-Plateau environment. The overall results indicate, however, that the variety ''Violet de Galmi'' might be more suited to the Jos-Plateau environment than the variety ''Red Creole'' in terms of the yield of onion bulb.KEYWORDS: Day length extension, Allium cepa L., Bulb yield
Highlights
Onion (Allium cepa L.) belongs is of the family Alliaceae
Bulb Weight Per Plant: The mean bulb weight increased with increasing day length extension and the difference between the day length hours was significant (P
Mean Number of Rings Per Bulb: The number of rings in each of the three bulbs sampled from each pot was counted and recorded as the number of rings per bulb
Summary
Onion (Allium cepa L.) belongs is of the family Alliaceae. The crop is most extensively grown on light soils, which may be sandy-loam or silt-loam with a pH range of 5.8 to 6.5 (Kochhar, 1986), and in some cases it thrives in a pH of 6.0 to 6.8 in some soils (Costa, 1995). Past the “juvenile” stage of leaf growth, the plant becomes sensitive to the bulbing stimulus that is triggered if the days are long enough (Ibrahim, 2010). When day length is at or greater than the threshold for bulb initiation of a particular cultivar of onion, bulbing occurs only if the average daily temperature is 60 °F (16°C) or above, and the average night temperature is 60–80°F (16–28°C) (Ibrahim, 2010). If the requirement for day length is not met (that is, the days are not long enough when the onion plant is physiologically mature), leaf production continues without bulb formation (Ibrahim, 2010). Bulbing response is reported to be stronger when night-time temperatures are low and the plants are large (Ibrahim, 2010)
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