Influence of Windbreaks on the Vegetative and Reproductive Growth
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 conditions (control). Wind speed was reduced by up to 50%within the shelters, depending upon ambient wind velocity. 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 per vine. The specific weight (mg dry weight ? cm 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 internode length of non-sheltered vines. Total yield per vine for the windbreak treatment was 10%greater than the control in 1991, and 20%greater than the control in 1992. Yield differences were a result of increased berry number per cluster and cluster weight in the windbreak treatment. Fruit from the treatments did not differ significantly in berry weight, soluble solids content, titratable acidity, or pH at harvest in either season. Stomatal conductance and carbon assimilation rate was slightly greater for sheltered vines than for unsheltered vines. The results indicate that windbreaks augment vine capacity by increasing total leaf area and magnifying cluster weight fruit via their effects on vegetative growth and cluster weight.