Operation effects of wind machines for frost protection of tea trees on different time scales

Frost protection effect experiments in tea fields were conducted according to wind machine operation timing on different time scales. The treatments of starting to use wind machines before tea sprouting,starting before frost occurrence and stopping after sunrise were set up respectively. And the impact of wind machine operation on the growth of tea trees,temperature rise in the canopy and protection coverage was measured. The results indicated that starting to use wind machines 20 d,15 d and 7 d before tea sprouting increased the length of young shoot,bud density and 100-bud weight by over 20% compared with the control test; Starting wind machines 2. 0 h,1. 5 h and 1. 0 h before frost occurrenceled to better protection and enlarged the coverage radius by more than 60% compared with the control test. Delayed stopping of wind machines by 2. 0 h,1. 5 h and 1. 0 h after sunrise reduced the temperature rise of the canopy by 45. 76% in the first hour,and narrowed the reduction of the photosynthetic intensity of tea leaves. Therefore,to protect tea trees from late frost cold for better growth and yield,the appropriate application of wind machines should be more than 7 d prior to the tea budding, and the operation timing of starting and stopping for a certain frost event should be 1. 0 h before frost occurrence and 1. 0 h after sunrise,respectively.