Effects of artificial soil covers on the internal temperatures of grape berries during the grape maturation

Air temperature as well as internal and surface temperatures (by infrared radiothermometry) of grape berries of vineyards (var. Syrah) under which we place different soil cover : bare soil, polyethylene and aluminium were monitored during the swelling and the ripening stages at the « Institut National de la Recherche Agronomique » experimental station at Pech Rouge, Gruissan (France). Results showed there were significant differences in the thermal responses of the grapes with respect to the type of soil cover and degree of fruit ripening. High differences in temperatures between grape and air were observed in soil covered with aluminium sheet which reflected most of the incident solar radiation. For this cover, biochemical analysis of berries and must indicate an increase of sugars grade and alcoholic degree. Statistical analysis were carried out to determine the influence of climatic variables on the grape temperatures. Solar radiation, wind and air temperature are the parameters which seem the main factors, nevertheless, their influence evolve during the process of grape maturation