Effect of Different Cutting Heights of Mechanically Pruned Grapevines cv. Merlot Over Three Consecutive Seasons

Abstract

The mechanisation of various vineyard operations reduces production costs and labour requirements, thus allowing for the more efficient management of larger vineyards. However, pruning mechanisation has been associated with yield decline (a decrease in fruit production due to the elongation of the fruiting positions out of the trellis system area), over cropping and unstable yields. Furthermore, manual followup has been a common practice for most vineyards subjected to mechanised pruning. A Merlot vineyard was studied for three consecutive seasons in terms of its vegetative and productive aspects, and hand pruning was compared with mechanised alternating pruning strategies. Bud burst was more successful in hand-pruned vines compared to mechanically pruned vines. However, hand pruning took longer and produced a lower yield compared to mechanical pruning. Traditional high (25 cm above the cordon wire) mechanical pruning showed deteriorating characteristics over time in vegetative and yield parameters. Vines pruned at a lower height (12 cm above the cordon wire) in one of the three seasons maintained high production. Despite higher yields, fruit soluble solids, pH and titratable acidity were not altered. The quantity of second-crop fruit from lateral shoots was small and was very similar among treatments. Mechanical pruning at a lower height in one season in general reduces the annual potential yield, but the average and cumulative effects over the years improve compared to using just traditional high mechanical pruning. These long-term effects make it feasible to fully mechanise vineyard pruning and maintain high yields.

The Effect of Spur Position and Pruning Severity on Shoot Development

“…However, further studies on the relationship between pruning severity and stored carbohydrates should be investigated to determine if there are changes in stored carbohydrates after several seasons and if vines adjust to these changes. The yield response observed in this study was similar to those published in previous studies in that yield is not only initially affected by the number of nodes but rather is impacted overtime [3,5,6,9]. In addition to collecting yield by position for each treatment, total vine yield by treatment was also collected (Table 8).…”

“…This method, referred to as minimal pruning, has shown an increase in yields and production during the first initial years [1,5]. However, several studies have shown that yield and berry quality begin to decline over several years of mechanical pruning due the increased number of buds retained per vine due to the reduction of pruning severity [5,9].…”

Influence of crop load on the yield and grape quality of Merlot and Vranac (Vitis vinifera L.) varieties in Trebinje vineyard

“…Results showed that early leaf removal followed by cluster thinning resulted in a lower berry mass and number of berries per cluster, and thus a lower yield. Peppi et al (2017) noted that an adjustment in mechanical pruning with regard to cutting height is a feasible alternative to obtain regular and sustainable yields in 'Merlot' with considerably lower labour inputs in the vineyard. On the other hand, the effect of crop load treatments on the content of bioactive compounds such as total phenolics and flavonoids in berries of Merlot and Vranac varieties has been less studied.…”