Abstract
Abstract: In order to efficiently solve the shading problem between the upper layer and lower layer in the same cultivation system and between adjacent cultivation systems in multi-layer stereo-cultivation of strawberry, and to improve the fixed A-shaped frame system, a novel sun-tracking cultivation system was developed, which could keep the line of cultivation frame parallel to sunray to make the best use of direct light. In this study, some instruments, including the CANUOL intelligent remote control door opener, supporting multi-function controller, and the time control switch, were installed on the fixed A-shaped frame. So the fixed frame could rotate about its central axis according to a preset procedure, and the door opener revolved through the multi-function controller operation, thus boosting the cultivation frame motion. Time controller may set the start time of cultivation shelf running, running times, running time interval and the time length of operation as cultivation shelf homing according to the different needs of different seasons. The operating parameters of the cultivation frame were determined according to the changes of solar elevation and azimuth of the sun in winter in Beijing, based on the characteristics of the light environment of Beijing. This test set the running time of the sun-tracking frame to be 9: 00-16: 00 every day from November 2015 to March 2016, rotating once every 55 min, and turning 9 times every day. In November and next February and March, the total daily movement angle was 103.5°, each rotation angle was 11.5°, and each exercise took 4 s; the total daily movement angle was 96°, each rotation angle was 10.5°, and each exercise took 3.6 s in December and January next year. Parameters could be adjusted according to the actual situation in the process of actual production and application. In this study, the strawberry planting time was September 8th, 2015, and the harvest time was from January 13th to March 17th, 2016. Experimental design was that 5 sun-tracking frames were set as the test group, and 5 fixed frames were as a control group; then the difference between the 2 light environments was compared, and the temperature of canopy and root, the yield and the profit of strawberry were used to validate whether the sun-tracking frames could improve light environment and increase the production. Results showed that integrated photosynthetic photon flux density (PPFD) of sun-tracking system was higher than that of fixed system on both middle and lower layers. Within 3 months of winter, compared with fixed system, integrated PPFD on upper, middle and lower layer of sun-tracking system increased by 28.0%, 79.3% and 38.6% respectively in the east side and 30.1%, 41.0% and 18.2% respectively in the west side. So, the sun-tracking frame could change the light-shielding. The strawberry canopy and rhizosphere temperature of the sun-tracking cultivation were better than the fixed stereo cultivation frame, and the minimum value of the cultivated strawberry rhizosphere temperature of fixed frame at each layer was lower than the sun-tracking cultivation frame. Meeting the most suitable rhizosphere temperature of 15-20 ℃ for upper, middle and lower layer of west side, the time of the sun-tracking cultivation frame was 60, 40 and 120 min longer than the corresponding position of the fixed cultivation frame, respectively. Accordingly, the time of the former canopy temperature below 5 ℃ was 130, 170, 230 min shorter than the latter, respectively. The strawberry yield per plant on sun-tracking frame was higher than the corresponding position on fixed frame. During the trial, compared with the fixed system, the strawberry output of the sun-tracking system was increased by 214.8 kg/667 m2. Benefits were increased by 6 498.5-12 942.5 yuan. So, the sun-tracking system can improve the light and temperature environment condition, which promotes the output of strawberry and benefit. Therefore, it is valuable cultivation technology and should be widely applied.
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