Growth and Bulb Characteristics of Extremely Early-Maturing Onion by Air Temperature Variation at Different Altitudes
2018
Song, E.Y., National Institute Horticultural Herbal Science, Rural Development Administration, Jeju, Republic of Korea | Moon, K.H., National Institute Horticultural Herbal Science, Rural Development Administration, Jeju, Republic of Korea | Wi, S.H., National Institute Horticultural Herbal Science, Rural Development Administration, Jeju, Republic of Korea | Oh, S., National Institute Horticultural Herbal Science, Rural Development Administration, Jeju, Republic of Korea
A study was carried out to determine the influence of climatic environments on the growth characteristics and bulb quality of extremely early-maturing type onion grown at different altitudes, such as 60m, 200m, 350m and 700m above sea level (ASL). The mean air temperature during the growing season of extremely early-maturing type onion (October 18 to April 27) was 10.8℃, 9.6℃, 8.1℃ and 6.1℃ at 60m, 200m, 350m and 700m ASL. The mean air temperature during the bulb growth period (March 16 to April 14) was recorded 10.5℃, 9.4℃, 7.9℃ and 6.0℃ at 60m, 200m, 350m and 700 m ASL. Plant height, neck diameter, leaf number, leaf area, top fresh weight and top dry weight were significantly increased in growing of extremely early-maturing type onion at 60m ASL. Bulb/neck diameter ratio increased rapidly under the same temperature regime. The diameter and weight of the bulb were also the largest at 60m ASL during the bulb growth period (daily mean temperature of 12.5℃). At 60m ASL, there was the highest bulb size like a height, diameter and weight of bulb related directly on onion yield in the bulb growth period from March 16 to April 14. In contrast, yield and bulb quality were considerably decreased at 700m ASL during the bulb growth stage (daily mean temperature of 8.4℃). The quantity of extremely early-maturing type onion has gradually decreased as the daily average temperature drops below 12.5℃ during the bulb growth stage (March 16 to April 14). As a result, the lower temperature (daily mean temperature below 12.5℃) during the bulb growth stage significantly decreased the size and quantity of bulb in direction proportion.
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