Revista de Agronom�a (LUZ); Vol 10, No. 2, 1993

Principio de Manejo de Copa en Vid y Pr�cticas Culturales para controlar el exceso de Vigor y Mejorar el microclima dentro del Follaje

Principles of vineyard canopy management and cultural practices for controllmg excess vine growth and improvement of the canopy microclimate

W. Mark Kliewer

Department of  Viticulture and Enology University of California, Davis, CA 95616-8749

Palabras claves: Vid, Canopy, Manejo, Vigor

lntroduction: Canopy management consists of any operation that produces a desirable canopy configuration, usually with the objective of improving canopy microclimate, fruit and wine composition, vine productivity, and reduction of  fungal diseases in fruits. Major emphasis of canopy management is usually to reduce excessive canopy shading and increase air circulation in the fruiting region. Canogy microclimate is the climate within and immediately around the canopy, i. e., the leaf and shoot system of a vine or vines. It differs from the above canopy ambient climate due mainly to the size, shape, arrangement and density of  leaves within the canopy Photosynthetic photon fluence rate (PPFR), red:far red (660/730 nm) ratio, wind speed, and evaporation rates are the climatie factors post influenced by grapevine canopies, whereas air temperature and humidity are much lesa affected.

Method : Fied experiments established at Davis, Parlier and Oakville, CA using Cabernet Sauvignon, Sauvignon blanc, Chenin blanc or Thompson Seedless have been conducted over the past 12 years to test the effects of different trellis-training systems, pruning levels and methods, shoot trimming, shoot positioning, shoot orientation, shoot density, and leaf removal in the fruiting zone as means of improving the canopy microclimate, fruit composition, vine growth and crop yields. Other canopy management practices, including vine spacing within and between rows, row direction, rootstocks, nitrogen fertilization, irrigation amounts, and length of cordon branches per vine are currently under investigation and preliminary results will be reported.

Results : Growth and yield indices for optimal canopy microclimate of Cabernet Sauvignon and Sauvignon blanc in the Napa Valley had the following characteristic: 4 m2 leaf area per meter canopy length, leaf layer number, and leaf area/surface area per vine of 1 to 1.5, total number of shoots/m canopy length of 12 to 18, pruning weight (kg)/m cordon length of 0.5 to 0.75, crop yield /pruning weight ratio of 4 to 9 and mean cane weight during the dormant period of 30 to 60 g. The effect of three row spacings (2.4, 3.O,and 3.6 m) in combination with two trellis systems (Single Canopy Bilateral Cordon (BC) and Divided Canopy Quadrilateral Cordon (QC) on shoot growth, crop yield and composition of Cabernet Sauvignon grown at Oakville, CA, was studied over a period of sig years (1987-1992). QC vines averaged 22.0 mtJh� compared to 18.9 for BC vines; the increase in yield was due to greater number of shoots and clusters per vine. At harvest (22.5 "Brig) QC fruits had lower Ph and higher anthocyanin than BC fruite. TA, malic acid and K did not differ significantly between trellis systems. QC vines had lees pruning wight and higher yield/pruning weight rutio than BC vines. Reducing row spacing &om 3.6 m to 2.4 m incrased crop yield by 33% or 6 mt/ha but reduced pruning wigth per vine fi om 3.4 to 2.6 kg. Row spacing had no significant efeect on fruit composition except TA was slightly lower at 2.4 m spacing that at the two wider spacings. QC vines had more shoots ut of small length and lees leaf area per shoot than BC vines. Row wigth was directly related to shoot number por vine and inversely related to wight per shoot. Sensory analysis reveled QC wines could be distinguished from BC wines.

Conclusions: Both light quality (R:FR ratio) and quantity (PPFR) effects on fruit composition and ripening of grapes were found.

Exposure of dense naturally shaded grape clusters (R:FR ratio < 0.1) to supplemental red light that increased the (R:FR ratio to 0.6 to 0.7) without significantly changing the PPFR, advanced the beginning of fruit ripening by seven to ten days, markedly enhanced berry weight and levels of sugar and anthocyanin in fruit and increased the activities of PAL, invertase and NR, enzymes. These fining indicate that both phytochrome and photosynthesis influence fruit composition and ripening of grapes. Leaf removal in the cluster zone as well as canopy division by trellising greatly improved the canopy microclimate, specially the PPFR and R:FR ratio in the cluster region. Closely associated with these microclimate changes were increased levels of sugar in fruits and reduction in titratable acidity, Ph, malate and potassium in berry juice, all generally considered positive for high wine quality Trellis systems that reduced interior canopy shading also had the added advantage ofincreasing crop yield, mainly through increase in development of shoots from basal buds that increased the number of clusters pervine as well as greater number of berries per cluster. Canopy division by trellising is a proven means of maintaining a desirable microclimate for high shoot numbers per hectare and producing high crop yield of quality fruit.