Late pruning, an alternative for rainfed vine varieties facing new climatic conditions

In Chile there is a dry farming area known as a traditional wine region, where varieties brought by the Spanish conquerors still persist. These varieties, in general, are cultivated under traditional systems, with low use of technical and economic resources, and low profitability for their grapes and wines. In this region, as in other wine grape growing areas, climatic conditions have changed significantly in recent decades. In particular, the occurrence of spring frosts, when bud break has already begun, have generated significant losses for these growers.

Under this scenario and in search of a low-cost alternative to mitigate the spring frost damage in the País variety, during the 2021-2022 season, late pruning was tested in phenological stages E4 and E9 (according E-L modified scale) compared to the winter pruning (PI). The results showed that, in relation to PI, the pruning carried out at E4 and E9 delayed bud break seven and 10 days respectively, and the differences in the phenological development remained until stage 32, when they were aligned. Pruning at E4 allowed better vegetative development than PI in terms of shoot length. Maturity was slower the later the pruning was, and at harvest time a difference of almost 2°Brix was registered between the late pruning and the PI. Regarding yield, differences in the number and weight of bunches showed that yields were similar in treatments E4 and PI, while E9 had a lower yield than PI.

Pruning at E9 is not be recommended since it generated a lower yield and presented problems in the bunch ripening uniformity, but pruning at E4 represents a great alternative to avoid spring frost damage and keep vineyard quality and yield.