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Influence of the climatic conditions of different localities in the greenhouse microclimate: Andean and central region of Venezuela

Abstract:

In Venezuela, the criterion for achieving optimal microenvironment for crop growth in greenhouses according to the local weather is a scarcely evaluated aspect, and the information on the microclimate within these structures is limited. In order to better understand it, measurements of climatic variables were carried out between 2006 and 2009 to evaluate the influence of climatic conditions at different localities in the microclimate of greenhouses. Hourly verage variables were generated for each location and greenhouse. The transmittances of photon flux density of photosynthetic radiation and of the incident solar energy were determined on the roof of the greenhouses; and also the ventilation flow rate proportional to the pressure drop. Correlations were found between variables measured inside of greenhouse: air temperature and solar radiation, air temperature and humidity, a linear correlation between the ratio (area side windows) / (floor area) and the rate of air exchange in the greenhouse, as well as differences between the total solar radiation available on the deck of the greenhouses. It is proposed that the roof of semi-elliptical shape may be more appropriate for tropical regions. A maximum greenhouse width of 18m is suggested, thus reducing the temperature difference inside to improved ventilation.