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Background and Aims In Marlborough's cool climate, slow ripening grapes often do not reach ripeness. This study determined the effect of crop load, achieved via different levels of retained node number, on Sauvignon Blanc phenology and ripening. Methods and Results Two to six canes, each single cane unit having 12 nodes, were laid down and from these vines phenological development was recorded and growth curves were calculated for budburst, flowering, veraison and ripening over 4 years, from 2007 to 2010. The different crop loads, obtained through these pruning treatments, had little influence on vine phenology until after veraison when the retained node number had a significant influence on the rate of accumulation of total soluble solids during the ripening period. Target ripeness was delayed by up to 41 days when 72 nodes were retained, compared with 24 nodes. Simple modelling with generalised logistic functions accurately described phenological changes in the plant and improved the reliability of statistical comparison of time courses between the different treatments. Conclusion For all 4 years of the study, differences in retained nodes per vine had little influence on the phenology of the vine up to veraison, but had a strong effect on the rate of ripening because of subsequent differences in crop load. After the first year of the trial, the influence of the retained nodes on yield gradually diminished and as a consequence so did the influence on the rate of ripening. Significance of the Study A clear demonstration of the strong influence of crop load on the rate of ripening of Marlborough Sauvignon Blanc, together with the capacity of the vines to adjust their source/sink balance over time, with the direction of the adjustment determined by the node number.

Abstract:We quantified the importance of postharvest carbohydrate assimilation and nitrogen availability to replenish vine reserves, over and above maintaining optimal growth, productivity, and fruit quality of high-yielding, vigorous Sauvignon blanc grapevines. To create different carbohydrate (CHO) and nitrogen (N) reserve concentrations, our factorial-design trial consisted of a postharvest defoliation treatment overlaid with a pruning treatment in which 48 or 72 nodes were retained on four-or six-cane vertical shoot positioned vines, respectively. In defoliation (Defol) vines, all leaves were removed immediately after fruit harvest, while foliated vines (Fol) went through normal senescence. From just after ectodormancy in 2008, samples of root and trunk tissue were taken throughout the years for CHO and N analyses and results were compared with annual yield data. Both defoliation and node number treatments reduced vine growth and yield. Additionally, differences in CHO and N of the permanent structure were found. Depleted winter reserves in trunk and root were replenished during the next growth cycle, suggesting that grapevine N and CHO partitioning favor survival of the permanent structure over increasing vine size and yield. However, after two consecutive years of defoliation, the cumulative effects of smaller, less fruitful canes from year one and reduced carbohydrates from the subsequent year reduced both yield and vegetative growth in the third growing season. Therefore, even the short-lived postharvest canopy in cool climates contributes to the vine CHO economy. Defoliation or excessive crop loads affected carbohydrate reserves in vines, but only after several consecutive years of low recharge; this manifested iteself in lower yields and poorer vegetative growth.

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Background and Aims Previous work has indicated that patterns of within‐vineyard variation in vine vigour are stable in time and, in the case of spur‐pruned vineyards, closely match patterns of variation in yield. However, whether this yield : vigour interaction also occurs in cane‐pruned vineyards is uncertain. This work sought to better understand this issue in support of efforts to improve yield estimation in cane‐pruned Marlborough Sauvignon Blanc. Methods and Results Vine vigour, measured as pruning mass, trunk cross‐sectional area and using remotely sensed imagery, and the components of yield were measured in a 5.9 ha Marlborough Sauvignon Blanc vineyard on vines which had been pruned to retain either two or four canes. The results suggest that whereas patterns of variation in vine vigour are stable in time, and related to variation in the land underlying the vineyard, patterns of yield variation are neither temporally stable nor related to variation in vine vigour or the inherent underlying characteristics of the block. Conclusions For all practical purposes, variation in the yield of Marlborough Sauvignon Blanc within vineyard ‘zones’ identified on the basis of variation in vine vigour or soil properties can be regarded as random. Nevertheless, given a diversity of product offering, and because variation in vigour can have a marked impact on fruit composition, remotely sensed indices of vigour do provide a valuable basis for targeting sampling or sensor deployment aimed at yield estimation. Significance of the Study This work highlights the need to differentiate between spur‐ and cane‐pruned vineyards in considering how vineyard variability should be assessed, and how the tools of precision viticulture and targeted management are applied.