2020 Volume 32 Issue 3 Pages 55-60
For greenhouse environmental control, the monitoring of crop transpiration rate is indispensable to optimize the irrigation schedule. In this study, we developed an open chamber method-based real-time transpiration monitoring system (RTMS) by using an inexpensive H2O sensor, which is able to be installed in commercial greenhouses. RTMS is composed of an open-bottom chamber and a sensing unit. The size of the chamber is 0.5 × 1.0 × 2.1 m (W × D × H) and it encloses two full-size tomato plants with transparent film. The three fans equipped at the top of the chamber exhaust interior air and the open bottom allows exterior air to move into the chamber. The inflow- and outflow-air were continuously sampled, and their H2O concentrations were measured by a SHT-35 that is an inexpensive air temperature and relative humidity sensor. The accuracy of RTMS was assessed with a high precision infra-red gas analyzer (IRGA) and proved that RTMS has enough accuracy to monitor the dynamic transpiration of tomato plants under greenhouse condition. Furthermore, RTMS successfully detected drought stress occurred in tomato plants, which was caused by stopping irrigation, as an obvious decrease in transpiration rate and total conductance. These results suggested that RTMS can be a useful tool to monitor the crop transpiration in commercial greenhouse to achieve the optimized irrigation schedule.
