Evaluation of winter pruning mechanization in a Touriga Nacional vineyard: A five-year study in Lisbon wine region

Abstract

Background: Terroir integrates the sensory attributes of wine with the environmental and human factors that shape grape production, including climate, soil, cultivar, and viticultural practices. Rising labor costs and the scarcity of skilled workers have stimulated increasing interest in the mechanization of winter pruning in the Lisboa wine region.

Aims: This study aimed to evaluate the effects of winter pruning mechanization on yield components and berry quality in a vineyard of Touriga Nacional located in Lisbon wine region.

Methods: A five-year field trial (2021–2025) was conducted at Quinta da Almoínha, Dois Portos, using 22-year-old Touriga Nacional vines grafted onto 110 R rootstock. The experiment covered a 0.20 ha plot arranged in a completely randomized block design with two replicates of ten vines each. Two pruning systems were compared: (i) short mechanical precision box-hedged pruning (SMP) with no manual correction of node number, and (ii) the conventional hand spur pruning (HP) used in the region. Both treatments were performed on the same date.

Results: Although SMP retained approximately eight times more buds per vine than HP (14–16 nodes retained), vines exhibited compensatory regulation that balanced yield. Budbreak decreased by about 60 % and shoot fertility by 35–40 % compared with HP. The number of berries per cluster, berry weight, and berry volume were also reduced under SMP (to 70 %, 90 %, and 95 % of HP, respectively), likely due to impaired flower formation, reduced fruit set, and source limitation. Nevertheless, SMP increased yield by 1.5-fold compared with HP, with approximately three times more clusters but half the cluster weight. SMP delayed ripening, resulting in soluble solids at harvest equivalent to ~90 % of HP values, while pH, malic acid, tartaric acid, and total acidity were not significantly affected.

Conclusions: Mechanized winter pruning influenced vine reproductive behavior, and delayed grape maturation but did not compromise key must parameters. With appropriate vineyard management, the mechanization of winter pruning can maintain terroir expression while enhancing operational efficiency. These results support the adoption of pruning mechanization as a resilient strategy for sustainable vineyard management in Lisbon wine region.