ENVIRONMENTAL CONTROL AND CROP PRODUCTION IN MEDITERRANEAN GREENHOUSES
The Mediterranean greenhouse production system is a low cost production system with limited climate control. As a consequence the greenhouse climate is at times suboptimal and the crop yield is suboptimal as well. Nevertheless well design and well operated Mediterranean greenhouses achieve a positive economic balance between their agronomic performance and the investment and operations costs. A general overview of the current production strategies and technology of the Mediterranean greenhouse industry is provided. The demand exists for year-round supply of high quality greenhouse products, but in the Mediterranean region the growing period is often limited due to the lack of proper climate control. Two basic strategies to overcome this problem are to enhance the greenhouse technology or to grow crops in two or more regions with harvesting periods that complement each other. Both production strategies must be respectful of the environment. Life Cycle Assessments conducted on passive greenhouses have shown that the major impact on global warming is due to the production of the steel structure, while fertiliser production and its use is the main reason for water eutrophication and air acidification. Concerning greenhouse technology the importance of improving light transmission and natural ventilation is discussed. New cladding materials such as IR reflective films are promising materials that allow maximum PAR transmission and optimal near infrared reflection for better air temperature management. Computational analysis studies have determined that ventilation can be enhanced by reducing the greenhouse width, by orienting the roof ventilators towards prevailing winds, by increasing the roof slope up to 30° and by using internal deflectors to produce better air mixing and more uniform internal climate. Other climate control methods such as shading, evaporative cooling and CO2 enrichment are also briefly discussed. A review of crop production techniques and management, plant protection issues, better use efficiency of water and other relevant aspects of the greenhouse industry lead to the final consideration of this paper. Production strategy and greenhouse technology have to be considered when developing the production package or system, in which all the specialized elements cooperate to reach the best potential result for each greenhouse operation.
Castilla, N. and Montero, J.I. (2008). ENVIRONMENTAL CONTROL AND CROP PRODUCTION IN MEDITERRANEAN GREENHOUSES. Acta Hortic. 797, 25-36
microclimate, climate control, production strategy, greenhouse technology, greenhouse management