Water Use of Cabernet Sauvignon Grafted onto Three Rootstocks in a Vineyard Near Oakville in the Napa Valley: Validation of Crop Coefficients and Regulated Deficit Irrigation Factors Developed in the Carneros District on Chardonnay

AVF Proj. ID: 158 / /Cat.: ,
Primary Investigator(s): Larry Williamsby

The last year of a three-year study was completed in a Cabernet sauvignon near Oakville in 2000. The objective was to determine the applicability of crop coefficients developed using Chardonnay in different vineyard with different cultivars, rootstocks and row directions. The three rootstocks used in the trial were 5C, 110R and 3309C. Potential ET (Eto) from budbreak (3 April) until harvest (21 September) was 875 mm (34.4 inches). Estimated full ET of the vines was determined by multiplying weekly Eto by the crop coefficients developed in Carneros. Water use at 100%of estimated Etc between the above two mentioned dates was equivalent to 209 gallons per vine (450 mm or 17.7 inches). Applied water in 2000 was equivalent to 187 gallons per vine.

Irrigation treatments at the vineyard were fractions (0, 0.25, 0.5, 0.75, 1.0 and 1.5) of estimated full Etc. Prior to harvest midday values of leaf water potential for the irrigation treatments at 100%of Etc or greater were less negative than ?1.0 Mpa. Vines that were deficit irrigated had midday leaf water potential values more negative than ?1.0 Mpa. There were significant irrigation and rootstock treatment effects on berry weight measured on 12 September. Berry weight was maximized at irrigation amounts from 75 to 100%of Etc while the rootstock 5C had the largest berries. There were no differences in soluble solids among treatments on the sample date. Rootstock had no significant effect on Ph and titratable acidity (TA). However, TA tended to increase as applied water amounts increased. Vines receiving no applied water or applied water at 0.25 Etc had the lowest yields. Vines receiving 75%of estimated Etc had the highest yield in 2000 (equal to 5.25 tons per acre). Wines were made as a function of irrigation treatment using fruit from all rootstocks. Wine color intensity and the total wine phenols index decreased as the amount of applied water increased. Two tasting panel sensory analyses indicated a preference for wine made from the 0.75 Etc treatment.

Over the three-year course of the experiment, berry weight was maximized at the 0.75 ETc irrigation treatment. This result is similar to studies I?ve conducted at other locations on wine grapes in the coastal valleys of California and on raisin and table grapes in the San Joaquin Valley. Pruning weights and yield were generally highest for the 0.75 ETc treatment in this study. Both parameters leveled off at applied water amounts above this treatment level. Yields of vines receiving no applied water, 0.25 ETc and 0.5 ETc were 66, 77 and 96%of the maximum yield, respectively. The results indicate that one could deficit irrigate this particular vineyard and have minimal effects on productivity, while increasing water use efficiency and providing beneficial effects on fruit quality.

PDF: Water Use of Cabernet Sauvignon Grafted onto Three Rootstocks in a Vineyard Near Oakville in the Napa Valley: Validation of Crop Coefficients and Regulated Deficit Irrigation Factors Developed in the Carneros District on Chardonnay

Modeling Grapevine Water Use

AVF Proj. ID: 159 / /Cat.: ,
Primary Investigator(s): Larry Williamsby

The last of a three-year study was completed in 2000. The data collected this past growing season was to establish crop coefficients for grapevines using different trellis systems. The seasonal crop coefficients were derived from the linear relationship between the crop coefficient and percent shaded area beneath a Thompson Seedless grapevine measured at solar noon (between 1230 and 1330 hours, PDT). The slope of this relationship was 0.017. The 0.017 value multiplied by the percent shaded area is the crop coefficient. For example, if the shaded area beneath a vine at solar noon is 20%of the total area allocated to the vine within the vineyard then the crop coefficient is 0.34 (0.017 x 20 = 0.34).

Several different trellis systems were measured at five locations throughout the State of California. These trellises included the lyre, GDC, VSP and vertically split canopies using the Scott Henry and Smart-Dyson trellis systems. Several additional trellis systems were also used such as the ?California Sprawl? and others using various crossarms to support the cordons and foliage catch wires. Shaded area under the vines was determined with the use of a digital camera and software to calculate shade in the image. Results indicated that a trellis that horizontally splits the canopy results in greater shaded area and therefore higher crop coefficients than a trellis that does not. The same is true for canopies that are vertically split compared to a trellis like the VSP. The crop coefficients also take into account row spacing.

At several locations, water meters were installed to measure the amounts of water the grower/cooperators applied and midday leaf water potential was measured. Applied water amounts were compared at the end of the season with estimated vineyard water use (Etc) during specific intervals. Estimated Etc was calculated as the product of Eto times the percent shaded area derived crop coefficients. In most cases when estimated Etc and applied water amounts were similar, midday leaf water potential values were less negative than ?1.0 Mpa (-10 bars). When applied water amounts were less than estimated Etc leaf water potential was more negative than ?1.0 Mpa. These results indicated that the derivation of crop coefficients from percent shaded area were useful in estimating actual vineyard water use at 100%of Etc.

The ability of grape growers to predict potential vineyard water is a necessity in California where water can be in short supply or expensive. One can estimate vineyard water use with the following equation: ETc = ETo x kc. Once this is calculated then deficit irrigation practices can be used such that a fraction of full ETc is applied to the vines either throughout the growing season or during specific phenological events. I have shown over the past several years that one can deficit irrigate grapevines such that water use efficiency is increased, yields can be either maintained or increased with high fruit quality for table, raisin and wine grapes.

PDF: Modeling Grapevine Water Use

Effect of Partial Rootzone Drying on Vine Water Relation, Vegetative Growth

AVF Proj. ID: 16 / /Cat.: ,
Primary Investigator(s): Sanliang Guby

Partial rootzone drying (PRD), derived from split root research, is an irrigation technique which modifies vine growth and development by keeping part of the rootzone dry and the rest of the rootzone well watered. The objective of this research was to investigate the feasibility and effect of PRD on vine water relation, vegetative growth, mineral nutrition, yield components, fruit composition, wine chemistry, and wine sensory characteristics in mature Sauvignon Blanc grapevines (Vitis vinifera L.) grown in the San Joaquin Valley of California, in comparison with conventional drip irrigation (CDI). Vineyard water use and canopy microclimate were also evaluated. This study was conducted in a 15-acre bilateral cordon trained mature Sauvignon Blanc/Freedom vineyard on Hanford Sandy Loam in the California State University, Fresno Agricultural Laboratory. Treatment factors included PRD and CDI at 0.4 or 0.8 evapotranspiration, resulting in 4 treatments, CDI-0.4, CDI-0.8, PRD-0.4, and PRD-0.8. Partial stomatal closure due to PRD resulted in a decrease in stomatal conductance (g), transpiration rate (E), and vine vegetative growth, and in turn, an improvement in water use efficiency. Yield, fruit composition and wine chemistry were not significantly affected by PRD treatment nor by the amount of water applied. Two years field experiments demonstrated that PRD offers a way for producing a vine with a better balance between vegetative and reproductive development, reducing vine water use, controlling vine vigor and canopy density, while maintaining crop yields when compared to standard vineyard irrigation practices. PRD holds potential to be a useful management practice for high vigor vineyards in the San Joaquin Valley of California. However, it seemed that most of the observed PRD effect on vine performance and vine physiology was resulted from the reduction of irrigation water rather than switching the wetting and drying sides. Further research is needed to investigate the necessity of alternating the sides of wetting and drying, because PRD consists of reduced amount of irrigation water and the switching.

Modeling Grapevine Water Use

AVF Proj. ID: 32 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

The last of a three-year study was completed in 2000. The data collected this past growing season was to establish crop coefficients for grapevines using different trellis systems. The seasonal crop coefficients were derived from the linear relationship between the crop coefficient and percent shaded area beneath a Thompson Seedless grapevine measured at solar noon (between 1230 and 1330 hours, PDT). The slope of this relationship was 0.017. The 0.017 value multiplied by the percent shaded area is the crop coefficient. For example, if the shaded area beneath a vine at solar noon is 20%of the total area allocated to the vine within the vineyard then the crop coefficient is 0.34 (0.017 x 20 = 0.34). Several different trellis systems were measured at five locations throughout the State of California. These trellises included the lyre, GDC, VSP and vertically split canopies using the Scott Henry and Smart-Dyson trellis systems. Several additional trellis systems were also used such as the ‘California Sprawl’ and others using various crossarms to support the cordons and foliage catch wires. Shaded area under the vines was determined with the use of a digital camera and software to calculate shade in the image. Results indicated that a trellis that horizontally splits the canopy results in greater shaded area and therefore higher crop coefficients than a trellis that does not. The same is true for canopies that are vertically split compared to a trellis like the VSP. The crop coefficients also take into account row spacing. At several locations, water meters were installed to measure the amounts of water the grower/cooperators applied and midday leaf water potential was measured. Applied water amounts were compared at the end of the season with estimated vineyard water use (ETC) during specific intervals. Estimated ETC was calculated as the product of ET0 times the percent shaded area derived crop coefficients. In most cases when estimated ETC and applied water amounts were similar, midday leaf water potential values were less negative than -1.0 MPa (-10 bars). When applied water amounts were less than estimated ETC leaf water potential was more negative than -1.0 MPa. These results indicated that the derivation of crop coefficients from percent shaded area were useful in estimating actual vineyard water use at 100%of ETC. The ability of grape growers to predict potential vineyard water is a necessity in California where water can be in short supply or expensive. One can estimate vineyard water use with the following equation: ETC = ET0 x kc. Once this is calculated then deficit irrigation practices can be used such that a fraction of full ETC is applied to the vines either throughout the growing season or during specific phenological events. I have shown over the past several years that one can deficit irrigate grapevines such that water use efficiency is increased, yields can be either maintained or increased with high fruit quality for table, raisin and wine grapes.

Water Use of Cabernet Sauvignon Grafted onto Three Rootstocks in a Vineyard Near

AVF Proj. ID: 45 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

The last year of a three-year study was completed in a Cabernet sauvignon near Oakville in 2000. The objective was to determine the applicability of crop coefficients developed using Chardonnay in different vineyard with different cultivars, rootstocks and row directions. The three rootstocks used in the trial were 5C, 11 OR and 3309C. Potential ET (ET0) from budbreak (3 April) until harvest (21 September) was 875 mm (34.4 inches). Estimated full ET of the vines was determined by multiplying weekly ET0 by the crop coefficients developed in Carneros. Water use at 100%of estimated ETC between the above two mentioned dates was equivalent to 209 gallons per vine (450 mm or 17.7 inches). Applied water in 2000 was equivalent to 187 gallons per vine. Irrigation treatments at the vineyard were fractions (0, 0.25, 0.5, 0.75,1.0 and 1.5) of estimated full ETC. Prior to harvest midday values of leaf water potential for the irrigation treatments at 100%of ETC or greater were less negative than -1.0 MPa. Vines that were deficit irrigated had midday leaf water potential values more negative than -1.0 MPa. There were significant irrigation and rootstock treatment effects on berry weight measured on 12 September. Berry weight was maximized at irrigation amounts from 75 to 100%of ETC while the rootstock 5C had the largest berries. There were no differences in soluble solids among treatments on the sample date. Rootstock had no significant effect on pH and titratable acidity (TA). However, TA tended to increase as applied water amounts increased. Vines receiving no applied water or applied water at 0.25 ETC had the lowest yields. Vines receiving 75%of estimated ETC had the highest yield in 2000 (equal to 5.25 tons per acre). Wines were made as a function of irrigation treatment using fruit from all rootstocks. Wine color intensity and the total wine phenols index decreased as the amount of applied water increased. Two tasting panel sensory analyses indicated a preference for wine made from the 0.75 ETC treatment. Over the three-year course of the experiment, berry weight was maximized at the 0.75 ETC irrigation treatment. This result is similar to studies I’ve conducted at other locations on wine grapes in the coastal valleys of California and on raisin and table grapes in the San Joaquin Valley. Pruning weights and yield were generally highest for the 0.75 ETC treatment in this study. Both parameters leveled off at applied water amounts above this treatment level. Yields of vines receiving no applied water, 0.25 ETC and 0.5 ETC were 66, 77 and 96%of the maximum yield, respectively. The results indicate that one could deficit irrigate this particular vineyard and have minimal effects on productivity, while increasing water use efficiency and providing beneficial effects on fruit quality.

Effect of Irrigation Frequency on Productivity of Thompson Seedless Grapevines

AVF Proj. ID: 9920 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

The second of a four-year study to investigate the effects of irrigation frequency on Thompson Seedless productivity was concluded in 1999. The irrigation frequency treatments included: a.) the application of water whenever the vines in a weighing lysimeter used 2mm (2.11 gallons) of water, b.) the application of water once a day (the amount being equivalent to the day’s use of water by the lysimeter), c.) the application of water every three days (the amount being equivalent to three days use of water by the lysimeter) and d.) the application of water once a week (the amount being equal to a week’s use of water by the lysimeter). In addition to the frequency treatments, water was applied in three different amounts: 60, 80 and 100%of lysimeter vine water use. Lastly, three different trellis treatments were included. The trellis treatments consisted of a single wire, a 0.6 m (2 ft) crossarm and a 1.2 m (4 ft) crossarm. Vine density in the vineyard was 1318 vines per hectare (533 vines per acre). Irrigation of the vines in the lysimeter and the rest of the vineyard commenced on April 19th. Vine water use between budbreak and bloom was 750 liters (200 gallons) per vine and between budbreak and harvest was 5800 liters (1534 gallons). The water use between budbreak and harvest was equivalent to 762 mm (30 inches). The amount of water applied to the 60, 80 and 100%of ET irrigation amounts was 58, 76 and 100%of actual vine water use (measured with the weighing lysimeter). Irrigation amounts had the predominant effect on midday leaf water potential. Averaged across the frequency and trellis treatments, the 60, 80 and 100%irrigation treatments midday leaf water potential values were -1.25, -1.08 and -0.91 MPa, respectively. There was a significant effect of irrigation frequency on berry weight. Irrigation amount and trellis type had significant effects on berry weight and soluble solids. However, there were no significant interactions among the treatments with regard to berry weight or soluble solids. The 60%irrigation amount had the smallest berries and the highest soluble solids. The single wire trellis had the smallest berries and thel.2 m crossarm had the highest soluble solids. There were no significant effects of the treatments on final yield. It is anticipated that two more years of study are needed to accurately assess the effect of irrigation frequency on Thompson Seedless productivity at this location.

Modeling Grapevine Water Use

AVF Proj. ID: 9939 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

Data were collected on Thompson Seedless grapevines grown in a weighing lysimeter April until July to refine a model of vine water use and then compare those results with actual water use. In addition, similar data were collected in a Chardonnay vineyard using a VSP trellis system with east/west rows, a Chardonnay vineyard using a quadrilateral cordon trained upon a 3-ft crossarm trellis with north/south rows and a Cabernet vineyard using a VSP trellis with north/south rows. The model was dependent upon the interception of sunlight by the vine and the relationship between light and stomatal conductance. Stomatal conductance also was dependent upon the canopy to air vapor pressure difference. Net radiation, vapor pressure and wind speed were measured above the canopy of all vines and recorded hourly. Once the necessary environmental data had been collected on a specific day and canopy conductance (gc) had been modeled, the data were inserted into a resistance-energy balance equation to calculate vine water use. Lastly, vine water use also was modeled by using the relationship between percent shaded area beneath a vine at solar noon and the crop coefficient. This was done at the above-mentioned locations and at four additional vineyards in which the appropriate crop coefficient had already been determined. There was a linear relationship (r2 = 0.99) between modeled water use and estimated (using ET0 and kcS at the wine grape vineyards) or measured water use (using the weighing lysimeter at the Kearney Ag Center) at all four locations. This linear relationship was obtained using data in which water use ranged from a low of 3 to a high of greater than 60 liters (approximately 1 to 16 gallons) per vine per day. While the modeled daily amounts of water were very close to daily actual water use, hourly values of vine water use (using the weighing lysimeter) were somewhat less so. The relationship between hourly modeled and actual water use of Thompson Seedless grapevines using data from five different dates was linear but the r2 was 0.92. There was a linear relationship between the amount of shaded area measured at solar noon beneath the Thompson Seedless vines within the lysimeter and vine ET and the crop coefficient from the beginning of the growing season until August. This relationship was then used to estimate crop coefficients at vineyard locations where I had already established the appropriate seasonal crop coefficients. There was a linear relationship (r2 = 0.82) between the crop coefficient estimated by measuring shaded area at noon and the crop coefficients I was using on the date the measurements were taken. It is felt that this method of determined non-water stressed crop coefficients would be the most practical means of estimating vine water use. The crop coefficients would then provide an objective method of scheduling vineyard irrigations for growers that would increase water use efficiency and optimize yield and quality.

Water Use of Wine Grapes Along the Central Coast of California – Validation of

AVF Proj. ID: 9946 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

A study was continued in three vineyards along the central coast of California to determine the applicability of crop coefficients and deficit irrigation factors established in a Chardonnay vineyard located in the Carneros district of Napa Valley at other locations. The vineyard sites were located at Gonzales in the Salinas Valley, Paso Robles and Edna Valley, south of San Luis Obispo. Potential ET (ET0) between budbreak and harvest at Gonzales, Paso Robles and Edna Valley was 997, 1023 and 959 mm (39.3, 40.3 and 37.7 inches), respectively. Estimated full ETC was determined by multiplying weekly ET0 by the crop coefficient developed in Carneros for 7-foot rows and then adjusted for row width at each vineyard. Calculated water use at 100%of ETC between the above two mentioned dates was equivalent to 402, 423 and 400 gallons per vine at Gonzales, Paso Robles and Edna Valley, respectively, while applied water at the same locations was 351, 337 and 353 gallons per vine. Irrigation treatments at each location were fractions (0.25, 0.5, 0.75, 1.0 and 1.25) of estimated full ETC. Maximum berry weight was obtained at irrigation amounts between 75 and 100%of estimated full ET treatments at all locations. Application of water at amounts greater than full ET did not significantly increase berry size. Soluble solids were significantly affected by irrigation treatments at all locations; the less amount of water applied the higher the °Brix. Rootstock and irrigation had an effect on berry pH. Titratable acidity was significantly affected by applied water amount as well as rootstock at all locations, however, there were no rootstock/irrigation interactions. Yields were not measured at the Gonzales site as the cooperator harvested the plots without prior notification. Rootstock had a significant effect on yield at the Edna Valley site. The rootstock 110R had the highest yield at that location followed by 5C while the lowest was Freedom. There was a significant interaction of rootstock and irrigation treatment on yield at the Paso Robles site. Yields of 5C and 110R tended to be maximized at the 0.75 irrigation treatment (leveling off with further increases in applied water) while yields of Freedom, 140 Ruggeri and 1103 Paulsen increased with more applied water. It should be pointed out that both 5C and 110R had delayed vegetative growth at the beginning of the 1999-growing season. It is unknown whether this was due to lack of soil moisture or to below average temperatures (or soil temperatures) early in the season. Pruning weights had not been measured as of the date this report was written.

Water Use of Wine Grapes in the Temecula Grape Region of California -Validation

AVF Proj. ID: 9947 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

The third (but last) of a four-year study to determine vine water use and effects of various irrigation amounts imposed either at bloom or veraison in the Temecula region was completed during the 1999-growing season. Calculated vine water use (ETc) from budbreak, March 25 to harvest September 24th, was 19.4 inches (1162 gal. Per vine). Applied water from the first irrigation (10 May) to harvest was 17.5 inches (1053 gal. per vine). A measure of vine water status (midday leaf water potential indicated that close to harvest these values were very similar to those recorded in 1998. Midday leaf water potential for the 25, 50, 75, 100 and 125%irrigation treatments were approximately -1.45, -1.35, -1.15, -0.95 and -0.9 MPa, respectively, each year. The application of differing amounts of water and time the treatments were imposed affected berry size and composition. Irrigation applications at the lowest amounts (25%of estimated ETc) reduced berry size by 32%when the treatments were imposed at bloom but less so when they were imposed at veraison. There was a significant interaction between irrigation amount and time the treatments were imposed. Maximum size resulted from irrigation amounts at 75 to 100%of estimated full vine water use. There were significant differences among irrigation treatments with regard to titratable acidity but not with soluble solids or pH. However, soluble solids tended to decrease as applied water increased. The time of irrigation applications did significantly affect pH and titratable acidity of the berries. There was a significant interaction between irrigation amounts and time of treatment imposition with regard to yield. Yield averaged across all treatments was approximately 8.1 tons per acre. Wines were made by the Callaway winery in 1998 as a function of irrigation amount and time of irrigation and assessed by myself and Callaway’s wine makers and vineyard personnel. Most individuals preferred wines made from application amounts of 75 and 100%of full ET. Based upon this tasting, wine was not made from the 25 or 50%irrigation amounts in 1999. Pruning weights were not taken after the 1999-growing season as the vineyard being used was severely affected by Pierce’s Disease. This also is the reason that the irrigation trial will not be conducted in the 2000-growing season.

Modeling Grapevine Water Use

AVF Proj. ID: 9849 / /Cat.: ,
Primary Investigator(s): Larry E. Williamsby

Data were collected on Thompson Seedless grapevines grown in a weighing lysimeter to refine a model of vine water use and then compare those results with actual water use. The model was dependent upon the interception of sunlight on each of the three canopy surfaces (top, north and south; row direction east to west) and the relationship between light and stomatal conductance. The canopy also was divided into sunlit and shaded leaf areas. Measures of total vine leaf area, shaded area and leaf area index (LAI) were also measured several times during the growing season. Solar and net radiation, vapor pressure and wind speed were measured above the canopy of the vines within the lysimeter. Once the necessary environmental data had been collected on a specific day and canopy conductance (gc) had been modeled, canopy resistance (l/gc) and aerodynamic resistances were inserted into a resistance-energy balance equation to calculate vine water use. There was a linear relationship between total leaf area per vine and shaded area per vine. As leaf area increased from 2 to 25 m2 per vine, shaded area increased from 0.8 to just less than 5 m2 per vine. The LAI (m2 leaf area m”2 shaded surface area) of the vines in the lysimeter increased up until total vine leaf area was 15 m2 per vine at which time it leveled off (at approximately 5.6 m2 m”2) with further increases in whole vine leaf area. There were linear relationships (r ‘s greater than 0.9) between vine water use and shaded area per vine and %shaded area per unit land area. In addition, the crop coefficient (kc) and total vine leaf area also were linearly related to vine water use (i^’s approximately 0.88). Modeled water use and actual water use on three dates (August 4 and 12 and September 6) late in the growing season were compared with one another. The two earlier dates were chosen as vine leaf area differed from August 4 to 12 due to cane cutting on August 8. Modeled and actual water use on August 4 was 12.3 and 12.28 mm, respectively. The model overestimated water use on 12 August and 6 September by 5.7 and 7.8%, respectively. On all dates tested, the model underestimated water use early in the morning and overestimated water use late in the afternoon. To obtain the above results, it was determined that canopy conductance was responding to VPD and therefore, gc was made a function of VPD (when the VPD was greater than 2.0 kPa.). Due to the lateness in which monies to conduct this study were received, water use was not modeled earlier in the growing season because the appropriate measures of canopy light interception had not been measured. The results collected in 1998 are promising but indicate that further refinement is needed both at the leaf and canopy levels.