The risk of frost occurrence in vineyards has decreased in recent decades due to the rise in temperatures associated with climate change. However, this temperature increase leads to an advance in the budburst phase, extending the period during which the vine is vulnerable to spring frosts.
While the vine is in vegetative dormancy, the risk of frost damage is low. By contrast, during budburst the plant’s vulnerability is at its highest. In this context, delaying budburst is considered a natural defence strategy against late frosts.
It is well known that delaying pruning until dates close to spring makes it possible to delay budburst, but it is still necessary to determine from which point this delay is effective, how many days budburst can be delayed, and what effects changes in pruning dates may have on other vineyard characteristics.
To evaluate the effect of different pruning dates on crop phenology, particularly during the initial stages, and to study their impact on vine growth, yield and grape quality.
The pilot trial is carried out in the municipality of Samaniego, in the Rioja Alavesa region, in a vineyard belonging to Bodega Ostatu.
The trial follows a randomised block design with four replications. The treatments correspond to different pruning dates carried out in November, December, January, February, March and April. Each elementary plot consists of 10 vines, distributed according to the block and the treatment applied.
During the 2023–2024 season, phenological observations are carried out for each elementary plot at the stages of budburst, flowering and veraison. In addition, weekly ripening monitoring is conducted during the four weeks prior to harvest, measuring parameters such as berry weight, probable alcohol content, total tartaric acidity, pH and malic acidity.
At harvest, vineyard yield is assessed by measuring production per vine and the number of bunches per vine, and samples are taken to analyse probable alcohol content, total tartaric acidity, pH, D-gluconic acidity and malic acidity.
