Trellises for Wine Grape Canopy Management in the San Joaquin Valley

A wine grape trellis trial was designed and planted in 1986 at the U.C. Kearney Agricultural’ Center in the San Joaquin Valley. The purpose was to determine the most suitable trellis system for optimum fruit production and composition in cultivars of major importance to the area; ease and economics of vine management and mechanization were also considerations. Two cultivars, French Colombard and Barbera, were tested on 8 trellis designs suited to mechanization over 3 years, 1989-91. Data collection involved measurements of vine growth and light environment and fruit characteristics and composition; wine making, must and wine composition, and wine sensory analysis were also performed. Contrast analysis was conducted on major comparisons of vine training and trellis configuration for individual years and all 3 years (overall effects). The addition of one foliage support wire above bilateral cordons (11″ distance) increased pruning brush weights; vine yield was also increased through increased berry and cluster weights and with little or no effect on fruit composition in both cultivars. Similar effects were also obtained by increasing the bilateral cordon height by 11″ in both cultivars and with some advanced fruit maturation in Barbera.

Vineyard canopy management practices for improving grapevine

The main conclusions from a four-year study of trellising, row spacing and pruning level of Cabernet Sauvignon at the Oakville Experimental Vineyard are as follows: 1. Reducing row spacing from 12 feet to 8 feet increased crop yield by 35{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} or 2.8 tons/acre with little or no significant difference in fruit composition. 2. At each of the three row spacings, quadrilateral cordon (QC) trellised vines produced approximately two tons/acre higher yield than bilateral cordon (BC) trellised vines averaged over a period of four years. 3. At the same level of “Brix at harvest, QC fruit had lower pH and higher levels of anthocyanins than BC fruit. 4. The higher level of anthocyanins in QC fruits than BC fruits was correlated to greater amount of photosynthetic active radiation in the fruiting region of the former treatment. 5. Increasing the pruning level from 24 to 60 buds per vine increased crop yield from 6.6 tons/acre to 11.0 tons/acre. 6. With increase in the number of buds per vine from 36 to 60 there was an average of 7 to 10 days delay in ripening. 7. At harvest, fruits from vines pruned to 48 and 60 buds/vine had lower pH, TA, malic acid and K and higher anthocyanin than vines pruned to 24 and 36 buds per vine. 8. Dividing the canopy, reducing distance between rows, and increasing the number of buds per vine all reduced shoot length, shoot weight, pruning weight per vine, and primary and lateral leaf area per shoot and increased the cropping efficiency. 9. The canopy density of QC trellised vines was significantly less than BC trellised vines. 10. Sensory analysis showed that BC wines could be distinguished from QC wines. 11. Sensory analysis could not distinguish between low crop wines (24 buds/vine) and high crop wines (60 buds/vine).

Water Conservation in Wine Grape Production

An infrared thermometer (IRT) was used to schedule irrigation in five vineyards. Chardonnay vines in Madera and Santa Maria, CA; Chenin Blanc vines in Madera, CA; and Cabernet Sauvignon vines in Madera and Paso Robles, CA were used in this project. Water was applied to drip irrigated vines only when IRT measurements indicated a certain level of water stress. If vines were below that stress level, water was withheld until stress increased to the selected level. Treatments were imposed from veraison to harvest at the Madera and Santa Maria locations; and from berry set to harvest at the Paso Robles location. Water use for irrigation was reduced by up to 3 0{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} in this study. The amount of water saved depended on environmental conditions and the irrigation scheduling practices of the grower-cooperator. Irrigation scheduling treatments had no significant effect on vine yield or dormant pruning weight. Fruit composition displayed only a small response to the treatment. In general, {aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} soluble solids of fruit were increased by increasing water stress. The effect of treatment on titratable acidity and pH was not consistent. These results are preliminary and several more years of data collection are required before equilibrium results can be obtained. Commercially available microsprayers were tested in the Center for Irrigation Technology Sprinkler Testing Laboratory on the CSU, Fresno campus. All microsprayers tested were not suitable for targeted frost protection of vines. Prototype microsprayers from two manufacturers were also evaluated. The Wade Manufacturing Pulsator was identified as being capable of providing adequate targeted frost protection with a flow rate of approximately 11 gpm/acre. Thus, the commercial application of this technology would substantially reduce water use for frost protection. Additional testing is needed to evaluate the Pulsator microsprayer under field conditions using differential application rates.

WATER REQUIREMENTS DURING AND AFTER VINEYARD ESTABLISHMENT FOR CHARDONNAY GRAPEVINES GROWN IN THE CARNEROS DISTRICT

A study was conducted to determine the water use or vineyard evapotranspiration (ET) of Chardonnay grapevines during vineyard establishment. ET is the combined loss of water by evaporation from the soil and transpiration by the vine. The experimental vineyard was located in the Carneros District of Napa Valley. In addition, the vines were grafted onto two different rootstocks (110R and 5C) to determine if there were differences in water use between them. Vineyard water use was determined by measuring soil water depletion and the addition of water during an irrigation. Soil water content was measured with a neutron probe (also called a hydroprobe or soil moisture gauge). Access tubes, needed to measure soil water content, were placed at eight sites throughout the vineyard (four sites per rootstock). At each site six access tubes were placed such that the soil water content in one quarter of the vine’s root volume could be quantified down to a depth of 3 m (10 ft) . The tubes were placed equidistant from one another: two tubes in the vine row, two tubes midway between rows and two tubes midway between the four tubes mentioned previously. The tubes also extended midway between vines within a row. The vineyard was planted with the rootstocks in June of 1990. In the Fall, the rootstocks were chip budded with Chardonnay scion buds. Starting the first week in July, soil water content (SWC) was measured at all eight sites (four sites per rootstock) weekly. Soil water content the first year declined slightly from the first measurement date throughout the remainder of the season. This indicated that the vineyard was irrigated at slightly less than vineyard ET during that time. Approximately 3 0{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} of the water used by the vines was supplied by the soil, with the rest being provided by the irrigation water. The total amount of water used by the vines (averaged across both rootstocks) from July until the end of October was approximately 117 mm (4.6 inches) of water. This was equivalent to 380 liters (100 gallons) of water per vine during that time. Potential evapotranspiration (ETJ , determined at the CIMIS (California Irrigation Management Information System) weather station at Oakville was 575 mm (22.6 inches) of water from July to the end of October. Potential ET is the calculated water use of a short, green, well irrigated reference crop (usually a grass) . The use of water by the grass is used for comparison with the use of water by other crops. ET? is needed to develop crop coefficients. In 1991, SWC increased during the first six weeks of the season indicating that the vines were being over-irrigated. After that, SWC decreased for the next six weeks and then remained constant from then until the end of October. These results indicated that the vineyard was irrigated at close to vineyard ET during the major portion of the growing season. Again, approximately 3 0{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} of the water used by the vines in this vineyard was supplied by the soil. The total amount of water used by the vines (average of the two rootstocks) from April until the end of October was 175 mm (6.9 inches) of water. This was equivalent to 563 liters (150 gallons) of water per vine. ET0 measured at the Oakville CIMIS weather station was 810 mm (31.9 inches). Leaf water potential was measured several times during the 1991 growing on the Chardonnay scions within the vineyard. Leaf water potential is a measure of the water status of a plant. It previously has been demonstrated that leaf water potentials less negative than -1.0 MPa indicate that the vine is not under water stress. In this study, leaf water potential values for vines on both rootstocks were less negative than -0.9 MPa, indicating that during the growing season the vines were probably not under stress. It also indicates that the vines had been irrigated at amounts close to what the vines actually used. The water used by the vines in this vineyard was less than half that used by grapevines growing in the San Joaquin Valley during similar periods of vineyard establishment. For example, vineyard ET was 300 mm (11.8 inches) and 400 mm (15.7 inches) of water the first and second years, respectively, for a Thompson Seedless vineyard compared to 117 (4.6 inches) and 175 (6.9 inches) for this vineyard during the same years of vineyard establishment. This would be expected as evaporative demand is much greater in the San Joaquin Valley compared to the Carneros district. In addition, this Chardonnay vineyard was not planted until the last week in June compared to an April 10 planting date for the Thompson vineyard (therefore, a shorter time period for taking measurements in the first year of vineyard establishment at the Carneros site). Another reason for the lowered water use reported here was that vine growth was much less for the Chardonnay vines compared to the Thompson Seedless vines grown near Fresno. The data contained in this report is the first the authors are aware of in which vine water use was quantified for vines grown in a cool climate during vineyard establishment. This study will continue for another four years, including years in which vines will be in full production. Lastly, crop coefficients will be calculated for each year of the study and then be used for future irrigation management practices.