Testing the possibility of mapping vineyards covered with plastic sheets by Copernicus Sentinel 2 imagery

Quantity and quality of crop production are markedly influenced by the natural variability of plant and field conditions and by erratic applications of cultural practices. Monitoring vine growth and vineyard conditions can improve the precision of input deliveries and help predict crop productivity and quality trends. Covering vineyard with plastic sheets to protect foliage and grapes from adverse climatic conditions is an increasingly common practice, especially in table grape plantings. Detection by remote sensing of vineyards covered by plastic sheets is currently a challenging issue given the intrinsic nature of plastic covers that are expected to heavily impact reflectance from the underlying vegetation. Plastic sheets are expected to affect the radiative transfer process from vegetation to sensor, introducing new approximations. They can change both signal transmission and absorption, and possibly generate artifacts in reflection due to their close-to-specular reflecting behavior. In this context, when trying to measure features of the underlying vegetation by remote sensing, a multi-temporal approach is mandatory. This study was conducted in Apulia (South Italy) with a focus on table grape vineyards covered with polyethylene sheets. Air temperature and shoot growth, were monitored during the 2016 season. Fourteen suitable Copernicus Sentinel 2 (Level 2A product) images were used to investigate if vine phenology can be similarly described with and without plastic covers. A time series of S2 Level 2A images were used, and the correspondent NDVI maps generated. The spectral signal was analyzed by comparing responses of two vineyards covered with different plastic sheets with two uncovered ones. Three tests were performed, including a comparison of data obtained from normalized difference vegetation index (NDVI) and modified soil-adjusted vegetation index version 2 (MSAVI2) spectral indices. All the results demonstrated that no significant limitations were introduced by plastic sheets while monitoring the spectral behavior of covered vineyards.