Excessive levels of solar radiation may negatively influence crop growth, with sunburns or other possible crop damages, while increasing the internal greenhouse temperature above levels that are tolerable for plants and workers. In order to control hot air temperature inside a greenhouse, one of the most common solutions traditionally employed by growers in Southern Europe is whitening the external side of its cladding material, by painting it with liquid calcium carbonate. More recently, the use of plastic shading nets is progressively affirming, thanks to their cheaper price and some improved technical characteristics that enable them to act as a “passive” tool for controlling internal microclimate and produce suitable environmental conditions. A comparative analysis between a plastic net and a traditional whitening technique, aimed to critically assess the efficacy of the two different shading methods to modify and control the internal microclimate inside a plastic-covered greenhouse, is presented in this paper. A trial was carried out in Pontecagnano (Southern Italy), where one small-scale tunnel was shaded with a plastic net characterized by 60% of shade effect, while another identical small-scale tunnel was whitened with liquid calcium carbonate on the external side of the cladding plastic film. The radiometrical characteristics both of the plastic net and the whitened film were determined in the laboratory of the SAFE School of the University of Basilicata (Italy). The results obtained through these experimental trails enabled a comparative analysis of the performances of the two tested shading methods, confirming the relationship among the shading conditions and the transmittance in the solar range, highlighting the role that a correct solution may play on the final results in terms of crop protection from high temperatures and sunburns
