Effects of anti-drip cover materials on microclimate and production of a hydroponic cucumber crop

Recent year's concerns about food safety, environmental pollution, worker's safety, resistance to chemicals and the need for rational use of energy stimulated extensive research concerning the development of alternative techniques in order to manage high humidity levels. Such a technique is the use of anti-drip (AD) and anti-fog (AF) polyethylene (PE) cover materials. Aim of this work was to study the effects of two AD PE cover materials on greenhouse microclimate and on growth and production of a hydroponic cucumber crop. The experiments were carried out from September to December of 2006 in three similar, heated greenhouses, covered by different cover materials. A standard greenhouse polyethylene (PE) cover film covered one of the three greenhouses (C-PE). The other two greenhouses were covered: the first by a PE film with anti-drip (AD) and anti-fog (AF) properties (AD+AF-PE) and the second one by a PE film with AD properties (AD-PE). The greenhouse and outside microclimate parameters along with crop growth and production were recorded. The results showed that the relative humidity levels were much higher in the AD-PE covered greenhouse. Furthermore, the temperature difference between the cover material and the dew point air temperature was more negative under the same greenhouse, leading in higher condensation rates over the PE film. The crop development and production was similar in the three greenhouses while the crop leaf area index values were slightly higher in the AD-PE covered greenhouse. Nevertheless, in order to control fungus development, the greenhouses covered by the C-PE and the AD-PE film needed about double fungicide applications, than the greenhouse covered by the AD+AF-PE film