Yield characteristics and environmental effects of plastic covers on table grape with relation to chemical, physical, radiometric and satellite analyses

Climate change poses a significant challenge for global viticulture, with growing evidence of its negative impact on thermal and hydric regimes, both of which are essential for the development of table grapes. The use of plastic covering in vineyards is a widespread technique aimed at protecting both vegetation and grapes from external factors. The covering modifies the microclimate and allows the extension of the harvest period by advancing or delaying grape ripening. This study investigates the effects of six different plastic films on table grapes using a multidisciplinary approach integrating chemical, physical, radiometric and satellite analyses. The study was conducted in 2024 in a commercial vineyard located in the countryside of Noicattaro in the Apulia region (Italy). Each plastic film had a different chemical composition, with specific spectral behaviour in terms of light transmission, reflection and absorption. The minimum and maximum temperatures, together with the relative humidity, were recorded for each plastic film to evaluate the environmental and production effects. Regarding the production results, significant differences were recorded in the case of the production parameter per plant (kg*vine) and, above all, in the case of total solid soluble per plant (TSS*vine). This last parameter, obtained from the product between the total concentration of sugars (°Brix) and the yield (kg*vine), reflects the real physiological conditions experienced by the plants. It varied from a maximum of 5.6 kg to a minimum of 3.3 kg, for the best and worst conditions respectively. These parameters, as well as other properties such as rheological and colorimetric features (CIE-Lab) were evaluated with significant differences. Continuous temperature and relative humidity measurements were recorded under the plastic films, giving the possibility to reconstruct the number of hours during which the temperature exceeded the physiological threshold of 35 °C. The results showed that the temperature increase was significantly greater with the warmest plastic cover, with 162 threshold exceedance events, while with the coolest cover, the threshold was exceeded only 3 times. This highlights the significant influence of the type of plastic on the heating of the underlying environment. The highest TSS value of 17 °Brix was recorded under the coolest condition, where the physiological threshold of 35 °C was exceeded only 3 times. The Sentinel-2 satellite played a crucial role in monitoring NDVI dynamics throughout the entire growth cycle, with specific corrections applied to minimize spectral interference caused by the plastic films.