ISHS Acta Horticulturae 206: Symposium on Grapevine Canopy and Vigor Management, XXII IHC
INFLUENCE OF HEDGING AND LEAF REMOVAL ON CANOPY MICROCLIMATE, GRAPE COMPOSITION, AND WINE QUALITY UNDER CALIFORNIA CONDITIONS |
| Authors: | M. Kliewer, A. Bledsoe |
| Abstract:
Leaves were removed off mature, quadrilateral-cordon trained 'Sauvignon blanc' vines at three separate times during the growing season--time 1, at shatter stage; time 2, four weeks after shatter; and time 3, seven weeks after shatter. At each of the three times, four levels of leaf removal were employed: control, (no leaves removed); level 1, basal leaves only; level 2, basal leaves plus a few leaves from top of canopy; and level 3, basal leaves plus leaves at top of south facing (Northern hemisphere) portion of canopy to form a distinct three-node wide window. Leaf area removed was 0, 22, 33, and 41 percent of total vine leaf area for the four treatments, respectively. Timing of leaf removal yielded no significant differences on yield components or fruit composition, although some effects of leaf removal were more evident in the earlier timings. Yield, cluster number, cluster weight, and berry weight were not significantly affected by the level of leaf removal. There were large effects on fruit composition due to leaf removal. Overall degree Brix was increased in leaf removal treatments. Titratable acidity, malic acid, pH and potassium concentration in fruit were all significantly reduced by leaf removal. In the month preceding harvest, percent of full sunlight in the fruiting region of the canopy averaged 5.3, 10.8, 23.8, and 32.3 for the four levels of leaf removal, respectively. Significant negative correlations were obtained between these average values and the means of the pH, malate, and potassium concentrations. A highly significant direct correlation was found between the levels of malate and potassium in the juice at harvest. In a vigorous Cabernet Sauvignon vineyard shoot topping to about 14 nodes at 5 weeks post bloom delayed fruit maturity, reduced berry weight, °Brix and pH of fruit when compared on the same date, but when fruit was compared at the same °Brix, there was little difference in fruit composition. Shoot topping markedly reduced the amount of bunch rot in wet years. Over a three year period, crop yield of topped and untopped vines did not differ significantly. | |
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