ISHS Acta Horticulturae 399: Greenhouse Environment Control and Automation
GREENHOUSE CLIMATE CONTROL - NEW CHALLENGES |
| Author: | B.J. Bailey |
| Keywords: | greenhouse, environment, control, ventilation, humidity, transpiration, carbon dioxide, irrigation |
| Abstract:
Increasing knowledge of the response of plants to their environment is providing new opportunities for greenhouse environmental control. To take advantage of this requires a better understanding of the physical processes which create the greenhouse environment. Where ever greenhouses are used ventilation is the key controlling process during the summer, but it is understood much less than heating. Knowledge of the air exchange rates is necessary so the effect of ventilation on temperature, humidity and CO2 can be quantified but, at present, there is no generic model of natural ventilation which can be applied to greenhouses with differing physical characteristics. This information could then be used together with the improved understanding of plant response to the environment, to define the best combination of conditions for cost effective plant production during the summer. An example is the optimal control of CO2 in which plant response is characterised by models of photosynthesis and photosynthate partitioning and the losses are determined using a ventilation model in order to determine the concentration which gives the maximum economic performance for the grower. Transpiration has been shown to be important for the growth and development of tomatoes, and there have been a number of studies on the physical aspects of this process. The greenhouse climate can be manipulated to increase transpiration but an increase in energy consumption might result. Information on the transpiration requirements of plants is desired so they can be provided in the most economical way. As the majority of irrigation water is used in transpiration, a reliable method of predicting transpiration could form the basis for the automatic control of irrigation. This would be of value in regions where the availability of water is limited. | |
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