Plastic greenhouse for growing wax apple: a strategy to meet the challenge of climate change

Wax apple (Syzygium samarangenes Merr. et Perry) is one of the most promising tropical fruits industry in Taiwan. Concerning the issues of dramatic climate change and the food safety. We simulated two models of greenhouses in coastal Yunlin County to investigate the development of wax apple plant and weather conditions in the greenhouse. Both greenhouses are mostly 5-m high arch strengthened truss plastic multispans, one is south to north, and one is east to west. The photosynthetic photon flux density (PPFD) in a new plastic greenhouse at winter daytime was around 600-700 μmol m^-2 s^-1 (while the average PPFD outdoor is 1700-1800 μmol m^-2 s^-1) but down to 300-500 μmol m^-2 s^-1 within a year because of the film aging and covering with sand and small particles. The pruning of the tree is under investigation for a more open shape to capture more incidences light. The maximum temperature of the multispans in summer was 40-43°C (36-34°C outdoor) while the minimum in winter was above 10°C (6-8°C outdoor). The side wall winches, circulation fans and top exhaust fans were helpful for ventilation. The drip irrigation supported with spray accessories were set to replenish water for plants. For organic practice in greenhouse, the control of diseases was easier than the control of pests. Moreover, the interactions between the microclimate of multispans and the nature of wax apple are new to explore, and we hope further greenhouse production would help to encourage the wax apple industry in Taiwan.