2018 ASHS Annual Conference

Majority of viticultural areas in California are characterized by non-limiting source of solar radiation during the growing season. A consequence of such solar radiation coupled with less than crop demand precipitation received result in water deficits during ripening. There is lack of information on determining appropriate balances of canopy management and applied water amounts to produce suitable yields without compromising berry chemistry. In response, a study designed to test the interactive effects of leaf removal timing (pre-bloom and post-fruit set, compared to an untreated control) and applied water amounts (1.0, 0.5 and 0.25 crop evapotranspiration replacement (ETc)) on Cabernet Sauvignon/110R in Oakville, CA. Stem water potential was lower in the 0.25 ETc regardless of leaf removal that led to a 40% reduction in net carbon assimilation This was mediated by a lower stomatal conductance with 0.25ETc. There was no effect of leaf removal timing on components of yield, including number of berries set. The 0.25 ETc treatment reduced berry mass and yield, but 0.5 and 1.0 ETc treatments were not different from each other. There was a significant interaction of leaf removal and irrigation on pruning mass and Ravaz Index. Reducing the applied water amounts resulted in significant effect on anthocyanin and proanthocyanidin content only when normalized dried skin mass (DSM) suggesting a concentration effect as opposed to an increase in biosynthesis. Leaf removal affected flavonol content, specifically kaempferol-3-o-glucoside both on DSM as well as a per berry basis which conformed to existing light exposure literature. Clear skies and long periods with minimal precipitation paired with severe reduction in irrigation will have a stronger influence on berry chemistry than leaf removal practices. Our results indicated that cluster microclimate without leaf removal was already optimized. Although not as impactful, there still appears to be potential for understanding leaf removal influence on berry physiology and its effect on vine balance in premium regions.