Reflections about optimal climate control in greenhouse cultivation.

Abstract The cultivation in greenhouses is characterized by a strong influence of the grower on the production process, made possible by the controlled crop environment. Up till now the potentials for optimal control of the greenhouse/crop system, however, have not been fully exploited. Given an optimal cultivation plan (sowing/planting date, schedule of horticultural operations, planned temperature regime, harvest, etc.), the diurnal control could be further optimized than is possible with present climate control systems. Improvements could be attained by incorporating present knowledge on diurnal growth processes and detailed knowledge on physical processes in relation to greenhouse climate in more intelligent control systems. Diurnal climate control is one of the tools of the grower to control the production process at the operational management level. The criteria for optimal climate control should be derived from the goals of the grower and have to be formalized explicitly for automatic control. To this purpose it is important to classify the major growth processes concerned according to response time and response type. In addition, interaction with the grower, with his specific know-how and responsibility, needs to be settled for proper integration with the management process and to provide information that cannot be collected automatically. A possible architecture of an optimal control system based on these principles is proposed.