Effect of Minimum Temperature on Budbreak and Subsequent Fruit Growth and Quality in Plastic House-grown ‘Maekawa Jiro’ Persimmon

Abstract

The purpose of this study was to determine the minimum air temperature to conserve energy under covering in forcing culture of 'Maekawa Jiro' persimmon. The plastic house was covered with a film and heated annually from 1997 to 2001 beginning in early January to keep the minimum air temperature above 10, 15, 18, or 20°C, until heating became unnecessary. Such temperatures affected the time of bud break and full bloom, but not the growth and quality of fruits. The number of days from covering to bud break (period I) and from bud break to full bloom (period II) was quadratically correlated with the mean minimum air temperatures during the respective periods. The quadratic regression equation suggests that bud break and full bloom was the earliest if the minimum air temperatures during periods I and II were kept at 16.5 and 16.7°C, respectively. However, lowering of the minimum air temperature by 3 and 2°C, respectively, would delay bud break and full bloom by only one day. Thus, by taking the heating cost into account, setting the thermostat at 13.5°C and 14.7°C during the periods I and II, respectively, is recommended.