Revista de Agronom�a (LUZ); Vol 10, No. 2, 1993
Sistemas de Conducci�n para mejorar la productividad del Vi�edo, el Microclima de la copa, la composici�n de la Fruta y la Calidad del Vino en California
Trellis training systems for imroving vineyard productivity, coanopy microclimate, fruit compositiow and wine quality in California.
W. Mark KIiewer* and M. J. Benz
Department of Viticulture and Enology University of California, Davis, CA 95616-8749
Palabras Claves: Vid, Conducci�n, productividad, Calidad, Vino.
Introduction: Modification of canopy architecture by trellis-training systems pro vides a relatively easy method of increasing the amount of exposed canopy surface area, photosynthetic active radiation, red:far red ratio and r�ducing shoot and fruit crowding. These changes in the canopy microclimate are generally acompanied by increased productivity as well as improvement in grape and wine quality. In recent years several new types of trellis-training systems have been designed that divide grapevines either horizontally or vertically into two or more separa te canopies. These include GDC, Lyre or U, TK2T, ScottHenry, and RT2T. The characteristics of these trellis systema will be presented.
Method: Two trellising trials were conducted at Davis; one comprised of a Single Canopy Bilateral Cordon (BC) and a divided canopy GDC and U trellis systems using Colombard and the second tria used the same trellising systems but with the cultivar Chenin blanc. Two additional trellising trials were conducted at Oakville int he Napa Valley comparing single and divided canopy trellis systems, with and without shoot positioning, and at pruning levels ranging from 24 to 60 buds/vine using Cabernet Sauvignon and Sauvignon and blanc over periods of 4 and 6 years, respectively.
Results: For Colombard, crop yield of BC, GDC. and Lyretrellsed vines averaged 14.8, 23.6, and 24.8 tons/ac, respectively, giving an increase of about 10 tons/ac for the two divided canopy systems over the BC. The increase in yield was due to greater number of clusters/vine and larger number of berries set per cluster. Berry weight of Lyre fruits was also significantly larger than BC and GDC fruits. The level of sugar and titratable acidity of fruits at harvest did not differ between the three trellis systems harvested on the same date. GDC fruits had lower pH and K than BC and Lyre fruits at harvest. The photosynthetic photon flux density (PPFD) in the fruiting zone of BC, GDC and Lyre trellised vines averaged 184, 437 and 348 EM-2S-1, recpectively. For Chenin blanc, GDC trellised vines had significantly greater PPFD, sunflecks, and red:far ratios in the fruiting region than Lyre and vertical trellised vines. The average crop yield of vertical, GDC and Lyre trellised vines averaged 37.5, 45.1, and 48.1 mt/hc, respectively. The higher yields of the GDC and Lyre vines was mainly due to increase in the number of shoots and clusters per vine. Lyre trellised fruits had higher oBrix, pH, and K, and lower titratable acidity and malic acid than GDC and vertical fruits. However, titratable acidity and malic acid of vertical fruits were significantly greater than Lyre and GDC fruits. The total phenols in the berry skins of GDC fruit were significantly higher than in vertical and Lyre fruits. Lyre trellised vines had the lowest evaporation potential in the fruiting zone and the highest incidence of botrytis bunch rot compared to GDC and vertical trellises. The amount of bunch rot was inversely relatad to the evaporation potential as measured with Livingston atmometers. For Cabernet Sauvignon, Quadrilateral Cordon (QC) GDC type trellised vines averaged 22.0 mt/ha compared to 18.9 for Bilateral Cardon (BC) vines; the increase in yield was due to greater number of shoots and clusters per vine. At harvest (22.5 oBrix) QC fruits had lower pH and higher anthocyanin than BC fruite. TA, malic acid and K did not differ signicantly between trellis systems QC vines had less pruning weight and higher yiel/pruning weight ratio than BC vines. QC vines had more shoots butof small length and less leaf area per shoot than BC vines. Sensory analysis revealed QC wines could be distinguished from BC wines. For Siuvignon blanc grown at Oakville, two distinetly separate canopies of foliage could be maintained if the distance between cordon branches was 0.6 m or greater. The optimum distance between cordon branches for maximum yield was 0.6 to 0.9 m. Divided trellised fruit had lighter berry and cluster weights, higher sugar but lower TA and malate than non-divided canopy fruits. The level of pH and K in fruits did not differ significandly between trellis width tratments. In the 6th and 7th years of this trial, shoot positioning significantly reduced bud fruitfulness, cluster size (number of flowers and berries per cluster) and the rate of sugar accumulation in fruits compared to non-shoot positioned vines. Hedginq or topping shots to 15 nodes soon after fruit set delayed ripening in each of the six years of the trial compared to vines not topped. Shoot topping had a larger effect on delaying fruit ripeninq.
Conclusions: Divided canopy trellis-training systens increased vineyard productivity without any apparent decrease in fruit composition or wine quality.