Effects of anti-drip polyethylene covering films on microclimate and crop production
One important issue for greenhouse producers to deal with is the management of high humidity levels during the cold period of the year. High level of humidity is a factor that directly affects the fruit yield and quality of greenhouse crops by pre-disposing these crops to fungal diseases. Recent concerns about food safety, environmental pollution, worker's safety and the need for rational use of energy stimulated extensive research concerning the development of sustainable humidity management techniques. Such a technique is the use of anti-drip (AD) and anti-fog (AF) 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 and tomato crop. The experiments were carried out from September to December 2006 and from February to May of 2007 in three similar greenhouses, covered by different cover materials. A standard polyethylene (PE) 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. 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.