Vine spacing of Vitis vinifera cv. Shiraz/101-14 Mgt. III. Grape and wine quality

Vine spacing effects of Shiraz/101-14 Mgt on a relatively high potential soil in the Breede River Valley, Robertson, South Africa, on grape composition and wine quality, were investigated. Canopies were VSP trellised and orientated approximately NNE-SSW. Spacing between rows was fixed at 2.2 m. In-row vine spacing changed from 0.3 – 4.5 m with increments of 30 cm (from 15151 – 1010 vines/ha). Grape composition and wine quality were monitored over six seasons and two grape ripeness levels. Decreasing trends of soluble solids (°B) and pH and increasing titratable acidity from narrow to wide spacing were observed. Sugar accumulation of wider spacings seemed delayed. Berry skin total anthocyanin index and phenol content showed virtually no change. Malvidin mono-glucoside and its p-coumaroyl and acetyl derivatives were present in the highest concentrations, followed by peonidin-, petunidin-, delphinidin- and cyanidin mono-glucosides and derivatives, each vine spacing treatment displaying a unique grape anthocyanin profile. The narrower spacing of vines seemed to favour skin anthocyanin accumulation compared to wider spacing. Decreasing trends in wine total anthocyanin intensity, anthocyanin density, and phenols were observed from narrow to wide spacing; all had higher levels in wines from riper grapes. Individual wine anthocyanin concentrations also showed qualitative profile changes. The first regression join points for all anthocyanins occurred around 1.8 – 2.4 m vine spacing; those for malvidin and derivatives consistently appeared at 1.8 m spacing. Although volatile compounds only seemed to respond to ripeness level and not to vine spacing, wine sensory quality generally decreased with wider vine spacing at both grape ripeness levels. Given the changes in biotic and abiotic growth conditions with wider vine spacing, the results likely displayed adaptation to the combined impact of increasing light exposure, berry temperature, physiological functioning, vegetative and reproductive growth ratios, and plant stress. The study showed the prominent role of plant spacing in sustainable grape growing and wine outcomes and thus the importance of judicious decision-making during the establishment and management of vines under any growth conditions and in any terroir.