Measurement and improvement of thermal environment in asparagus greenhouse

Abstract

Asparagus (Asparagus officinalis L ) is conventionally grown outdoors However due to natural disasters and vermin affecting yield and quality asparagus has been grown in greenhouses in recent years Taiwan is located in the subtropical zone and thus greenhouses there tend to retain heat and produce high temperatures When the surface temperature of the soil exceeds 33°C the asparagus spear tends to split at the tip which reduces its market value To increase the yield of greenhouse asparagus the environmental changes in a greenhouse must be understood as the basis for subsequent improvement of the internal thermal environment In this study vertical monitoring was adopted to record the temperature humidity and soil moisture content of the greenhouse Cameras were also employed to record the greenhouse environment and the process of asparagus growth A computational fluid dynamics simulation was conducted to determine the optimal mechanical ventilation plan The research results revealed that the environmental temperature and moisture content in the soil were critical for asparagus yield This study adopted an innovative strategy to reduce the local temperature in the soil There are many ways to cool the greenhouse which needs to be adjusted according to the crops grown and the local climate conditions In order to obtain efficient mechanical ventilation through FlowDesigner to simulate mechanical ventilation The airflow distribution and wind speed are simulated and analyzed in different scenarios and finally the optimization strategy of fan installation is obtained It can reduce the air temperature of 35℃ in the greenhouse to 33℃ Specifically we used temperature-controlled drip irrigation equipment to improve the asparagus growth environment After implementing this improvement the yield was higher than that of the conventional canal irrigation method This method is expected to increase asparagus quality and yield and resolve the problems of split spear in summer and insufficient yield in winter

Date of Award	2020
Original language	English
Supervisor	Tzu-Ping Lin (Supervisor)