Effect of mechanical hedge pruning on growth, yield and quality of Cabernet Sauvignon grapevines

The effect of mechanical hedging was studied over three growing seasons in a trial set up at a commercial vineyard, located at Cartaxo viticultural region (39 degrees 10` N; 8 degrees 45' W) with the variety 'Cabernet Sauvignon'. Compared with the conventional spur hand pruning (control), the hedged vines had a three times higher crop load in the first season and five fold in the following two seasons. Those high cropping levels induced a reduction in the budburst and in shoot and leaf size. However, as a consequence of a higher shoot number, the total leaf area per vine was similar to the control. During the ripening period the hedged vines showed a more negative predawn leaf water potential, but it did not affected significantly the photosynthetic rate, measured at midday on adult exposed leaves. Compared with the control shoot fruitfulness was smaller in the hedged vines but bunch number and yield per vine were significantly higher. With the exception of the total wine phenols in 1985, which was higher in the control, the must and wine quality where not significantly affected. Due to a significant reduction on shoot weight the hedged vines showed a smaller pruning weight in the first two seasons but in the third one, the values were similar to the control. According to those three season results the mechanical hedging seems to represent a technique which can be used in this ecological situation on cordon trained vines without strong negative effects on wine quality and vine longevity. However the significant reduction recorded in the wine total phenols recommend long term trials to confirm those preliminary results.