This project quantified the role of cluster microclimate in water stress responses, tested the importance of stress at veraison, and extended what we learned about seasonal water stress in hillside Cabernet franc and Sauvignon blanc production in Napa Valley to additional sites and varieties. Soil and vine water status is readily controlled in drip-irrigated vineyards of Pinot noir (Carneros) and Cabernet Sauvignon (Lodi). Changes in vineyard water status, yield, and fruit and wine composition caused by pre- (Early Deficit) and post-(Late Deficit) veraison stress were similar to our earlier results. Thus, those results, showing control of yield and fruit composition, can largely be extrapolated to valley floors and are not indicative only of hillside vineyards with shallow soils and high exposures. The results also show the utility of drip irrigation for control of vine water status and the prevalence of water deficits in winegrape production in the North Coast. Thus, many growers can control vineyard water status and, because of this, color, phenolics, malate, and amino acids, and other compounds in the fruit. Light penetration into the canopy increased in Early Deficit vines early in the season compared to other treatments. After veraison light penetration increased slowly in C vines and rapidly in Late Deficit vines, in part due to differences in the rate of leaf drop. The role of microclimate in the stress responses of fruit development was investigated with reciprocal treatments that, e.g., created in some well-irrigated vines a canopy that mimicked the canopy of Early Deficit vines and vice versa. Temperature in the cluster zone did not differ significantly among any treatments, and, therefore, was unlikely to explain the differences that we observed in fruit and wine composition. However, differences in the light environments were important in establishing part (less than 50%) of the decreased pH and and increased color of Early Deficit wines. This shows that water deficits can be used to improve canopy structure. Water stress at veraison was not found to be critical for controlling fruit composition. However, the timing of the water stress was important in determining sensory attributes because judges could easily discriminate between wines made from Early Deficit and Late Deficit vines.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1992-11-17 12:02:542019-01-22 18:58:35The Regulation of Fruit Growth, Fruit Composition, and Wine Composition by Water Management