Efficiency of Plastic Nets for Greenhouse Shading

Agricultural production is influenced by extreme weather phenomena, accompanied by major global changes, such as the increasingly sudden and frequent appearance of new types of insects, the transformation of eating habits (e.g., “smart/super foods”), etc. Thus, the concept of crop protection under greenhouse, conceived as a mere passive defense, is gradually being overcome: no longer a shelter “against” or “protecting”, but rather an intelligent structure “for” or “proacting". Plastic materials used to cover a greenhouse for the purpose of crop protection can play a crucial role on the quality of light hitting crops, controlling radiation in different ways, especially in the PAR wavebands. Covering materials and shading strategies can be suitably selected and implemented in many mild climate areas, as well as in warm regions where spring/summer solar radiation levels are often too high. To study the shading effect, in the present research some field trials have been performed, by covering different small-scale tunnels with a plastic film and protecting them with an outer plastic net (PRISMA HDF®), fixed at different distance from the plastic film for each tunnel. Temperature of air and of soil covered with a layer of black mulching fabric have been measured, together with solar radiation. The results confirmed that the thickness of the gap between shading net and plastic film plays a role on the internal microclimate, which may differently improve the thermal efficiency of the greenhouse and its overall thermodynamic behavior.