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The Spanish professor Martínez de Toda reports in the Vitis Journal of Grapevine Research on a technique that can delay grape ripening in very warm wine-growing regions and shift it to a cooler time.
The technique also allows for two grape harvests a year. The researcher from the University of Rioja further reports that the composition of the grapes from the second harvest is significantly better than that of the first harvest. The later harvest yields smaller grapes and berries with a lower pH value, higher acidity and a higher anthocyanin content.
For several years, Martínez de Toda has been researching ways to mitigate the effects of climate change through targeted shoot pruning. In previous trials, the grapes of the main shoot were removed, which led to a greatly reduced harvest. In the trial currently described, the main shoot is only pruned above the sixth nodium and the grapes are retained. By breaking the apical dominance, rapid side shoot growth is forced on the one or two uppermost nodes. The side shoots in turn form fruits. In the trial, the grapes of the main shoot ripened about 13 to 15 days later and the grapes of the side shoots about 35 to 57 days later than those of the unpruned control plants. In terms of quantity, the second harvest was about 30 percent of the main harvest. The shoots were pruned at the end of flowering. The two-year field trial was conducted with Garnacha, Tempranillo and Maturana tinta vines in a two-arm cordon system. Although longer-term studies are necessary, all indications are that the grapes of this double culture ripen well and that sufficient carbohydrate reserves can also be formed for the following year.
(ru / Source: Vitis Journal of Grapevine Research; Photo: pixabay)