Abstract:

The study aims to find out the difference and relationship between the orchard temperature and meteorological temperature of late-maturing citrus in Nanchong of Sichuan Province in winter, as well as the change and difference of temperature and humidity in small area under different weather conditions and cold prevention measures, and lay a foundation for exploring and summarizing suitable, efficient and safe overwintering technology of late-maturing citrus in Nanchong. In this study, a systematic field-test was carried out for the first time in Nanchong, which used common plastic film, cold-proof cloth, single-layer fruit bag, double-layer fruit bag with white outside and yellow inside to conduct comparative experiments. The temperature and humidity changes of each treatment under different weather conditions were monitored, and the orchard temperature and corresponding meteorological temperature were observed and compared. It was found that the orchard temperature and meteorological temperature had discrepancy under different weather conditions. When the meteorological temperature was high, especially at noon on a sunny day, the orchard temperature would be higher than the meteorological temperature, and when the meteorological temperature was low, such as under frost, rain and snow, the orchard temperature would be lower than the meteorological temperature. Through the linear regression analysis of the orchard temperature and meteorological temperature, the relationship expressions of Jialing (T₁) and Xichong (T₂) test points were T₁=1.458T_Q-3.114(R²=0.931) (T_Q stands for meteorological temperature) and T₂=1.379T_Q-2.293(R²=0.909), respectively. That was, when the meteorological temperature was about 0.76℃ and 0.21℃ in the two test points respectively, the orchard temperature would reach -2℃, and citrus fruits would suffer from freezing damage. Under different cold protection measures and different weather conditions, common plastic film and cold-proof cloth had the best effect on maintaining and improving orchard temperature. Cold-proof cloth could also significantly reduce the number of days of low temperature and the duration of low temperature, at the same time, no matter what kind of weather conditions, the variation range of humidity in cold-proof cloth treatment was the smallest, and the internal environment was relatively stable. According to the results of this study, cold-proof cloth is the best choice for winter routine protection of late-maturing citrus in Nanchong, and it is very important to establish a linear relationship model between orchard temperature and meteorological temperature for late-maturing citrus to overwinter.

Key words: late-maturing citrus, overwintering, meteorological temperature, orchard temperature, cold-proof cloth