Influence of Windbreaks on the Vegetative and Reproductive Growth

Spring and summer months in the Salinas Valley are characterized by strong daily winds. It is widely held that vine growth and productivity in this region are reduced due to the presence of excessive wind. Chardonnay, the major wine grape cultivar of this region, appears to be particularly sensitive to excessive winds. Salinas Valley wine grape growers have recently expressed interest in the use of windbreaks to increase vegetative and reproductive growth. The long-term effects of windbreaks on vine vegetative growth, yield components, fruit composition, and wine quality have not been adequately investigated. A study was initiated in spring of 1991 to determine the effects of windbreaks on the vegetative and reproductive growth of Chardonnay grapevines in the Salinas Valley. Grapevines grown in artificial wind shelters were compared to grapevines exposed to ambient wind (control). Wind speed was reduced by up to 50%within the shelters, depending upon sensor distance above ground. Marked differences in the vegetative and reproductive growth of sheltered and non-sheltered vines were observed in both seasons. Sheltered vines had significantly larger primary and lateral leaves, and greater primary and total leaf areas compared to the control vines. The specific weight (mg dry weight-cm’2 leaf area) of both primary and lateral leaves was greater for the control than for sheltered vines. The number of nodes per shoot was similar for both treatments, however, the internode length of sheltered vines was significantly greater than the internode length of non-sheltered vines. The rate of shoot growth was also significantly greater for sheltered vines than for non-sheltered vines. Stomatal conductance and carbon assimilation rate were slightly greater for sheltered vines than for unsheltered vines, while no difference was found in leaf water potential between the treatments. Significant differences in vine yield components were not observed between the treatments in 1991. However, in 1992 cluster number, cluster weight, and fruit yield of sheltered vines was greater than for non-sheltered vines. Fruit and must composition were similar for both treatments. The results indicate that sheltered vines produced higher yields than non-sheltered vines due to their greater vegetative growth and vine capacity. Sensory evaluations of wines produced in 1991 and 1992 will be performed in the upcoming season.