In sustainable or organic vineyard systems, the introduction of cover crops could represent a powerful tool for farmers to influence, positively, the agro-ecosystem by promoting the whole soil-plant system equilibrium. Concerning table grape production, nitrogen fertilizers are medium-high; for environmental aspects, organic viticulturists are more interested in legume inter-row cover crops. Research on cover crop effects was carried out in 2015–2016, on organic table grapes (the Sugranineteen variety) in Mediterranean conditions. Three inter-row soil management techniques were compared: (TR) inter-row spacing was cultivated with subterranean clover; (V) inter-row spacing with common vetch incorporated in the soil as green manure, and (RC) inter-row spacing with common vetch flattened by the roller crimper technique, making a living mulch. No significant difference was recorded in grapevine water status among the treatments. RC vines performed the highest net photosynthesis rate from shoot growth to veràison. Cover crops did not affect cluster weight, berry weight, and juice composition; however, they influenced berry detachment force. Our research findings confirmed that legume cover crops (subterranean clover and common vetch) increased soil organic matter and could represent an economic and sustainable soil use to reduce the amount of nitrogen fertilizers applied in table grape production.

It is known that early removal of basal leaves improves the exposure of cluster to direct sunlight and UV radiation, which positively influence the phenolic compounds and anthocyanin concentration of berries. This study was carried out to evaluate the effect of leaf removal applied before flowering to the basal zone of the canopy at different sides (fruit-zone north canopy side, south canopy side and north–south canopy side, respectively) of Aglianico vines trained to vertical shoot position system and row oriented to east–west (EW). The study was conducted in the controlled and guaranteed designation of origin (CGDO) Castel del Monte area (Apulia region, Italy). The treatment did not affect yield per vine, and nor sugar, pH, and total acidity of grapes. When it was applied to the basal south canopy side, the concentration of proanthocyanidins and total polyphenols of grapes increased, as well as antioxidant activity. In particular, anthocyanins content, determined by HPLC, increased by 20% with respect to control when treatment was applied to south and north–south canopy sides. Interaction between season period and treatment was found for all anthocyanins except for petunidin-3-coumaroyl-glucoside. Basal leaf removal applied to the north canopy side caused an increase in malvidin-3-O-glucoside content in grapes in 2016 and 2018, but not in 2017. Our results indicate that basal leaf removal (six basal leaves removed from the base of the shoots) before flowering (BBCH 57) can be used as an effective strategy to improve grape total polyphenols, anthocyanins concentration and antioxidant activity in vineyards cultivated under warm climate conditions. The treatment could represent a sustainable alternative to manual cluster thinning since it does not reduce yield per vine and can be performed mechanically.

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