Whole-of-block experimentation for evaluating a change to canopy management intended to enhance wine quality

Background and Aims:  Earlier papers have shown the utility of the whole-of-block approach to viticultural experimentation for assessing the relative merits of different mid-row management strategies to improve vine vigour, and ‘reduced input’ spray programs for the control of fungal disease. Here, a similar approach was used to evaluate alternative canopy management strategies as a means of improving grape and wine quality in a Shiraz vineyard in the Coonawarra region of South Australia. Methods and Results:  Two different canopy management strategies were compared: the existing practice of spur pruning to 45–50 buds per vine and shoot trimming (control) in comparison to spur pruning to 35 buds per vine, shoot thinning and shoot trimming (SPST). Contrasting treatment effects, both in terms of treatment response and its spatial extent, were observed during the trial. In 2005, the SPST treatment led to a significant improvement in some fruit quality parameters and a decline in yield. In 2006, significant treatment effects were only observed for bunch weight and the number of berries per bunch. Whilst reasons for these contrasting effects could not be deduced from the available data, it was demonstrated that the inherent variability of vine vigour within the block had a greater effect than the applied treatments. Conclusions:  Consistent with the other whole-of-block experiments described in this series, we conclude that this experimental approach offers advantages in comparison to plot-based approaches to viticultural experimentation. The spatial information obtained in this study created a better understanding of inherent vineyard heterogeneity and the effects this has on control options for vine vigour and grape composition than would have derived from a plot-based experiment. Significance of the Study:  This study is the first application of the whole-of-block experimental approach to assessment of alternative canopy management options. The work provides further demonstration of the value which accrues through using spatial variability as an experimental tool.