RESEARCH REPORTS Effects of Irrigation on Wine Grape Growth and Fruit Quality Richard Allen Hamman, Jr.,1 and Imed Eddine Dami2 ADDITIONAL INDEX WORDS. cold hardiness, soil moisture, soluble carbohydrates, Vitis vinifera Cabernet sauvignon, drip irrigation, wine color, pruning weight, crop load, total soluble solids, vineyard canopy SUMMARY. Field studies were con- ducted to determine the effect of three drip irrigation regimes on grapevine growth, juice and wine quality, soil moisture, cold hardiness of bud and cane tissues and soluble sugar content of cortical cane tissues of Vitis vinifera, Linnaeus ‘Cabernet Sauvignon’. This study was developed to help provide some irrigation management strategies that would improve fruit quality and reduce excessive vigor. Irrigation treatments of 192, 96, and 48 L (51, 25, and 13 gal) per vine per week were initiated at bud break until veraison (initiation of berry color) and then reduced by 25% through harvest. Significant differences of fruit weight per vine, crop load, soil moisture, average berry and cluster weight, shoot length and pruning weight per meter of canopy row were observed among treatments. Juice and wine compositions and wine color were also significantly different; however, cold hardiness and soluble sugar contents did not differ between treatments. Colorado State University, Orchard Mesa Research Center, 3168 B1/2 Road, Grand Junction, CO 81503. This research was conducted at the Canyon Wind Vineyard, Palisade, Colo. The authors acknowledge the cooperation of Norm Christianson, the owner of Canyon Wind Wine Cellars, and the support and technical assistance of Susan Baker, Refugio Diaz, John Wilhelm, Diane Ross, and Pepe Seufferheld. This work was supported in part by the Colorado Wine Board. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertise- ment solely to indicate this fact. 1Former viticulturist. 2Former PhD research assistant, viticulture laboratory, Colorado State University, Orchard Mesa Research Center, Grand Junction, Colo. 81503. 162 ● January–March 2000 10(1) ommercial wine grape vines are stressed 2 weeks before full were concerns in this ‘Cabernet production in Colorado bloom when cluster initiation begins Sauvignon’ vineyard since this cultivar C is mainly located on the west- (Jackson and Lombard, 1993; Smart is often characterized by excessive vigor. ern slope of the Rocky mountains in and Coombe, 1983). Water stress oc- If vine growth is not controlled by Mesa and Delta counties (Hamman, curring immediately after fruit set, in- irrigation management, then the ex- 1993). These areas can be described as fluences cell division and early cell pensive alternative of trellis modifica- semiarid, desert-like regions where total enlargement causing reduced poten- tion to a divided canopy would be annual rainfall typically ranges between tial berry size at harvest and thus re- needed. The goal of this research 150 and 380 mm (6 and 15 inches). duced yields. Water stress between project was to evaluate irrigation man- Therefore, irrigation is necessary for veraison and harvest can result in rapid agement strategies that would help quality fruit production. Summers are leaf senescence and abscission and even- determine whether the canopy could normally hot with cumulative growing tual loss of canopy, contributing to be managed and fruit quality improved degree days (1 Apr. to 31 Oct. 10 °C fruit sunburn (Smart and Robinson, through perfected irrigation tech- base (50 °F) averaging 1,885 at Or- 1991; Kliewer et al., 1983; Coombe niques. The specific objectives of this chard Mesa Research Center in Mesa and Dry, 1992). High levels of stress experiment were to evaluate the effects County (Hamman, 1996) and relative during this period will result in an of different irrigation rates on shoot humidity ranges between 20 and 60%. abscission of shoot tips. length, yield components, and fruit Soils vary widely in these areas and It is well documented that grape- and wine compositions. Also, during range from well-drained, shallow, sandy vines will grow excessively if provided the dormant season, the effects of irri- soils to deeper clay loams that retain with an abundance of water and fertil- gation treatments on bud and cane more moisture. Winegrape yield and izer (Jackson and Lombard, 1993; cold hardiness, water content, and quality are affected by climate, soil, Smart, 1985; McCarthy and Coombe, soluble sugar content were determined. genotype, and cultural management 1984; Smart and Coombe, 1983). Ex- This research project was conducted practices including irrigation (Smart, cessive shoot growth has been associ- during the 1997 growing season. 1985). Poor irrigation management ated with poor fruit set, poor fruit bud can result in water stressed or overly initiation for the following season, in- Materials and methods vigorous vines resulting in unbalanced creased powdery mildew (Uncinula IRRIGATION TREATMENTS AND SOIL growth, reduced yields and inferior necator Burr) pressure, a better habitat MOISTURE MEASUREMENTS. The 7-year- fruit quality (Bravdo and Hepner, for insects and lower fruit quality old ‘Cabernet Sauvignon’ vines used 1986; Jackson and Lombard, 1993; (Evans, et. al., 1990; McCarthy and in this experiment were own-rooted. Smart and Coombe, 1983). Coombe, 1984; Smart, 1985; The vines were trained to a bilateral Grapevine water stress can occur Wample,1997). Excessive shoot cordon system and spur pruned. The if the supply of water to the roots is less growth requires more cultural man- trellis system used was a six-wire verti- than the evaporative demand. The agement input, i.e., hedging, leaf pull- cal shoot position trellis. The vineyard cause for the stress may be low avail- ing, and shoot thinning to produce has a vine density of 2392 vines per able soil moisture, high evaporative quality fruit. Lateral shoot growth and hectare (968 vines per acre) based on demand conditions, unbalanced reduced vine acclimation can occur 1.5 by 2.75 m (5 × 9 ft) spacing. The shoot/root systems, a poorly devel- from over irrigating following a water- soil was a sandy loam (60% sand, 22% oped root system, high salt levels or a stressed episode (Smart and Coombe, silt, 18% clay) with a pH of 8.1 and an combination of these (Evans et al., 1983). Under these conditions, a de- organic matter content of 2%. An analy- 1993; Smart and Coombe, 1983; lay in fruit maturation could occur and sis of a soil saturation extract taken in Wample 1997). Unlike tomatoes (Ly- if vines are exposed to extreme low December 1996 and showed a soluble copersicon esculentum L.), immediate temperatures, bud, cane and trunk salt level of 0.30 mmhos/cm (0.12 signs of current season water stress are survival could be reduced. It is now mmhos/inch), which is considered not clearly visible with grapevines. recognized by growers and vintners adequate and nonhindering for grape- Symptoms are typically observed after worldwide that in regions with little or vine growth (Coombe and Dry 1992). repeated episodes of water stress (Jack- no rainfall during the growing season, The soil drains very well and contains son and Lombard, 1993; Kliewer et careful vineyard irrigation strategies no hardpans within a 122 cm (48 inch) al., 1983; Evans et al., 1993; Wample, should be used as a tool to control depth. Soil moisture measurements 1997; Porter, 1996). grapevine canopy growth and fruit were made with a neutron probe Water stress can affect grapevine quality characteristics (Evans, et al., (model 503 DR1.5 hydropobe; Camp- development in several ways. Water 1990, 1993; Jackson and Lombard, bell Pacific Nuclear, Martinez, Calif.) stress at bud break can result in uneven 1993; McCarthy and Coombe, 1984; at 0.3, 0.6, and 0.9 m (1, 2, and 3 ft) or stunted shoot growth. Under se- McCarthy et al., 1987; Smart and Rob- depths every 2 weeks beginning on 5 vere conditions nutritional deficien- inson, 1991). May until harvest on 7 October. The cies can occur. Poor flower develop- probe was calibrated before measur- ment can occur on water stressed vines Objectives ing, as described by the University of and, under severe conditions, flower This experiment was designed to California (1989). The neutron probe abortion and cluster abscission may evaluate current drip irrigation prac- access holes, approximately 122 cm occur (McCarthy, 1984; Coombe and tices for ‘Cabernet Sauvignon’ at the (48 inch) deep, were drilled under Dry 1992; Smart and Coombe, 1983). Canyon Wind Vineyard located in Pali- each vine row and within 30 cm (12 The following season’s crop potential sade, Colo. Excessive growth, reduced inch) from an emitter. Polyvinyl chlo- may be significantly reduced if the fruit quality and excessive irrigation ride (PVC) pipe with a 3.81 cm (1.5 ● January–March 2000 10(1) 163 RESEARCH REPORTS inch) diameter and a 114 cm (45 inch) rate was verified for each row by mea- actual nitrogen. The fertilizer (ammo- length was securely placed in each suring the flow rate of ten emitters. nium sulfate) was applied by injecting drilled hole. Each PVC pipe was The irrigation system was modified it through the irrigation system at bud plugged with a rubber stopper and with manual valves installed at the break, and on 1 June, 10 July and 5 covered with a plastic cap to prevent head of each row. Depending on the August. Netting for protection against entry of rainfall or irrigation moisture. treatment, the valves were manipu- birds was applied the second week in The PVC pipe access tubes allowed lated during each irrigation for volume August during veraison. Powdery mil- repeated, undisturbed soil moisture output control. Volume per irrigation dew was controlled with standard spray measurements. Each treatment had was controlled by manually shutting applications of sulfur and sterol inhibi- three neutron probe access tubes.