Agronomical effects of mechanical box pruning in cv. Merlot at central area of Spain

Abstract

Introduction: Global warming, economic crisis and globalization are the three pillars which are altering the world in all the domains. In viticulture, a shortening of the grapevine phenology and an imbalance sugars/acidity derived from the new climatic conditions are forcing a reshuffle of the way of working in the field, in a more productive and sustainable with better quality. For that reason new pruning techniques have been developed in a way to adapt grapevines to the new conditions. Mechanical Box pruning has been proposed as promising alternative to implement in Mediterranean regions as a way to compensate the shortening of the phenology. Material and methods: Trials have been carried out in central region of Spain, working with irrigated vines of Vitis vinifera L. cv Merlot trained in vertical shoot positioning bilateral cordon system. Three pruning treatments were tested: T1 and T2 were traditional two-bud spur, and T3 Box pruning, with no lateral shoot or sucker removal in T2 and T3. Yield and ripeness parameters same as must phenolic composition (Glories method) were analyzed from early veraison until harvest. Results and discussion: T3 vines showed higher yields compared to T2 and T1 reaching 28t/ha; 20t/ha and 12t/ha respectively. Higher canopy soil shade was also detected in T3 suggesting greater canopies and photosynthetic activity. Water efficiency was also higher in box pruning compared to manual pruning. No significant differences were detected at harvest concerning berry weight and must yield per berry. A delay in ripeness in T3 was clearly observed specially in TSS. Must composition showed differences at harvest in ph, TA and TSS between treatments being lower in T3 compared to manual pruning but all of them kept up in normal quality ranges. No differences were observed concerning phenolic composition, TPI or anthocyanins extractability. Conclusions: Box pruned vines show a higher productive behavior in a more economic and sustainable way with not big differences in terms of berry size or must quality, representing a valid alternative to produce higher yields with similar quality as the traditional spur pruning being well adapted to the new climatic and economic implications worldwide. Legislation should be adapted to new conditions and techniques making easier the implementation of new alternative methods.