Bunch protection techniques against thermal increase linked to climate change

Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de La Rioja, Gobierno de La Rioja). Finca La Grajera. Carretera Burgos, km 6. 26071 Logroño, La Rioja, España

Abstract

Increases in temperature and solar radiation, associated with climate change, can cause damage to the berry that causes processes of discoloration, dehydration, cracking or raisining, which can have a negative impact on the oenological potential of the harvest. This damage is called “sunburn” and occurs with some frequency in sensitive varieties such as Graciano. In order to mitigate these impacts, a shading technique has been proposed using protection nets that try to prevent the bunches from receiving excessive sun exposure. The experience shown in this work has been carried out during the years 2021 and 2022, using nets with shading capacity of 50% and 70%. The results have shown that the nets have significantly reduced the temperature of the bunch, also avoiding damage from sunburn. Besides, the organic acid content of the must has reached slightly higher values in the treatments with netting, compared to the control, but not significantly. In wine, the polyphenolic load has shown a variable behavior depending on the year, possibly conditioned by the variations in yield linked to the sunburn. The tasting panel has shown a certain inclination towards the wines from the net treatments in both campaigns.