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RESEARCH REPORTS Effects of Irrigation on Growth and Quality

Richard Allen Hamman, Jr.,1 and Imed Eddine Dami2

ADDITIONAL INDEX WORDS. cold hardiness, soil moisture, soluble carbohydrates, vinifera , drip irrigation, , weight, crop load, total soluble solids,

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 content of cortical cane tissues of , 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 (initiation of color) and then reduced by 25% through . 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 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, 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 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, 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 ( 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 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 (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 (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- 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. Three off the valve after the desired running tors and no disease was observed in any soil moisture measurements per tube time was completed. This manual irri- treatment. per date were recorded. gation schedule was employed three GROWTH CHARACTERISTICS AND YIELD The experimental design was a times per week. T-1 received 8 h of run COMPONENTS. Shoot length, cluster randomized block consisting of three time per irrigation which was equiva- weight and berry weight were mea- irrigation treatments and three repli- lent to 64 L (16.9 gal)of water. T-2 sured on two dates corresponding to cations. Each replicate (row) consisted received 4 h of run time per irrigation different developmental stages. At har- of 53 to 62 vines. Each treatment was which was equivalent to 32 L (8.4 gal) vest, yield components including aver- an irrigation rate expressed in liters per and T-3 received 2 h of run time per age cluster and berry weights and yields vine per week. Treatment 1 (T-1), 192 irrigation which was equivalent to 16 were determined. Average cluster and L (51 gal) per vine per week was the L (4.2 gal) of water. In order to allow berry weights were made by harvesting control. Treatment 2 (T-2) was half of timely shoot maturity and fruit ripen- 10 vines per row and randomly select- T-1, 96 L (25 gal) per vine per week. ing, all treatments were subjected to a ing 10 clusters. Berry weight was de- Treatment 3 (T-3), the lowest rate was 25% irrigation reduction on 11 August termined by randomly sampling ber- 48 L (13 gal) per vine per week. The (veraison) through 10 Oct. (harvest). ries from the selected clusters and vineyard drip irrigation system was a All standard vineyard cultural prac- weighing 10 berries per cluster. Yields pressurized, filtered system with two tices except hedging were employed. per vine were determined by dividing 4-L·h–1 (1-gal/h) emitters per vine The treated vines were not hedged for the harvest weight of each row by the and was used to supply each replicated measurement purposes of shoot length number of producing vines. Average treatment independently. One pres- and pruning weight. Weeds were me- pruning weights were also taken on 30 surized delivery pipe supplied water to chanically controlled. The vines were Dec. to determine the crop load of this zone of the vineyard and therefore fertilized with four applications of ni- each treatment.The crop load, as de- modifications for individual treatment trogen at 8.4 kg·ha–1 (7.5 lb/acre) for scribed by Smart and Robinson (1991), control were needed. The emitter flow a total of 33.6 kg·ha–1 (30 lb/acre) of is the ratio of fruit weight to pruning

Fig. 1. Soil moisture profile of three irrigation treatments imposed on ‘Cabernet Sauvignon’ vines grown at the Canyon Wind Vineyard in Palisade, Colo., 1997. Measurements represent the means of the top 0.91 m (3.0 ft) of soil. 83.33 mm·m–1 = 1.0 inch/ft. Bars indicate SE. Significant differences at P < 0.05 were observed for all three treatments on 28 July using Tukeys multiple comparison test.

164 ● January–March 2000 10(1) weight. Ten vines per row were ran- ing to 50% survival (T50) was deter- ture measurements were taken on 5 domly selected, spur pruned to 35 to mined using the Spearman-Karber May 1997, one day before a scheduled 40 buds/vine and average weights of method (Bittenbender and Howell, irrigation. This period corresponded the were determined. Juice 1974). to bud break of ‘Cabernet Sauvignon’. composition measurements at harvest WATER CONTENT. Bud and cane On this date, all treatments had similar consisted of sugar (% total soluble sol- tissues were also measured for water soil moisture content (Fig. 1). How- ids), pH, and titratable acid content content. Fresh weights of the sectioned ever, subsequent moisture readings (TA, in g·L–1). Wine composition mea- buds and 20 mm canes (0.78 inch) in indicated significant differences among surements were done in January after length were measured independently treatments throughout the season. T- the wine was stabilized but before any within 4 h of collection. The tissues 1, receiving the highest irrigation rate, fining or additions. The wine lots were dried at 70 °C (158 °F) for 7 d had the highest soil moisture. While were not replicated. Three separate and dry weights were taken. Moisture T-3, with the lowest irrigation rate, wine samples were taken from each content was calculated and expressed had the least. T-2 was intermediate wine lot and analyzed. The wine mea- on a fresh weight basis. (Fig. 1). Peaks observed in Fig. 1 cor- surements were TA, pH and wine color. SOLUBLE CARBOHYDRATES IN CANE respond to greater soil moisture re- Color analysis was made with a CORTICAL TISSUES. The relationship be- sulting from rainfall during summer Beckman 640 DV-UV visible spectro- tween treatments and soluble sugar thunderstorms. Although irrigation photometer (Beckman Instruments accumulation in cane cortical tissues rates were reduced by 25% on 11 Au- Inc., Fullerton, Calif.). Color density was examined. It was hypothesized gust, soil moistures peaked in mid- and absorbency at the 420 and 520 nm that reduced irrigation levels may alter September as a result of an unusual wavelengths were measured using spec- the vine’s capacity to produce high and significant rainfall (76 mm over 48 tral evaluation methods developed by levels of soluble and thus re- h). In general, the soil moisture profile Somers and Evans (1997). duce its cold hardiness. Cane cortical closely followed a pattern expected as COLD HARDINESS. Cane and bud tissue from each treatment was pre- a result of the imposed irrigation treat- cold hardiness was measured during pared and analyzed, as described for by ments. the dormant season in November, Hamman et al. (1996), using a Dionex SHOOT AND FRUIT GROWTH CHARAC- December and January. On each date, DX-300 series high pressure liquid TERISTICS. Canopy size differences dormant bud and cane tissues were chromatography system (Dionex Co., among treatments were visible at bloom collected and placed in plastic bags. Sunnyvale, Calif.). The concentration (11 June), when T-3 with the lowest Samples were subjected to gradual of five soluble sugars (fructose, glu- irrigation rate appeared to have the freezing by lowering the temperature cose, sucrose, raffinose, and stachy- shortest canopy height by this date 4 °C·h (8 °F/h) in a Tenney Jr. ose) were quantified and were ex- compared to T-1 and T-2. Measure- programable freezer (Tenney Engi- pressed as mole per gram on a dry ments, however, were not taken until neering Inc., South Brunswick, N.J.). weight basis. one month after bloom, and at veraison Each treatment was removed at 2 °C STATISTICAL ANALYSES. Analysis of (Table 1). On both dates, shoot and (4 °F) intervals, for each of four stress variance was performed on each ex- immature fruit growth was dramati- temperatures –20, –22, –24, and –26 periment and treatment means were cally influenced by irrigation treat- °C (–4, –7.6, –11.2, and –14.8 °F) compared using Tukeys multiple com- ments. Lower irrigation rates in T-2 chosen to span the probable lethal parison test (Gomez, 1984). The sta- and T-3 resulted in shorter shoots, temperature on a particular sampling tistical analysis was performed using smaller clusters and lighter weight ber- date. The bud and cane samples were software from Graphpad Prism Ver- ries than did those of the highest rate then thawed to 4 °C (39.2 °F) for 24 sion 2.0 (GraphPad Software Inc.,San in T-1 (Table 1). Similar findings were h, held at room temperature for 48 h Diego, Calif.). reported by McCarthy et al., (1987). and then excised and examined for We conclude that the reductions in browning (Stergios and Howell, Results and discussion shoot and fruit growth in T-2 and T- 1973). The temperature correspond- SOIL MOISTURE. The first soil mois- 3 are responses to water stress imposed

Table 1. The effect of irrigation treatments on 1997 growth characteristics of ‘Cabernet Sauvignon’ at different pheno- logical stages.

Phenological Shoot length Avg cluster Avg berry Date stage Treatmentz (cm)y wt (g)x wt (g) 11 July One month after bloom T-1 201 bw 95 b 1.7 c T-2 150 a 67 ab 1.0 b T-3 132 a 46 a 0.7 a 12 Aug. Veraison T-1 264 b 107 a 2.0 b T-2 188 a 100 a 1.7 a T-3 160 a 91 a 1.6 a zT-1 = 192 L (51 gal), T-2 = 96 L (25 gal), T-3 = 48 L (13 gal). y2.54 cm = 1.0 inch. x28.35 g = 1.0 oz. wWithin a column, means followed by the same letter are not significantly different at the 5% level using Tukeys multiple comparison test.

● January–March 2000 10(1) 165 RESEARCH REPORTS

Table 2. The effect of irrigation treatments on 1997 yield componentsz, pruning weightsy and crop load of ‘Cabernet Sauvignon’.

Avg Avg Pruning wt/ Crop load cluster berry Pruning m of yield/ wt wt Yield Yield wt canopy row pruning wt Treatmentx (g) (g) (kg/vine) (t/ha–1) (kg/vine) (kg/m–1) (kg/vine) T-1 136 bw 2.9 c 4.8 ab 11.6 1.0 b 0.65 4.8 a T-2 109 ab 2.3 b 5.2 b 12.5 0.7 a 0.40 7.4 b T-3 83 a 1.7 a 3.6 a 8.5 0.5 a 0.30 7.2 ab z28.35 g = 1.0 oz, 0.45 kg = 1.0 lb; 1.49 kg·m–1 = 1.0 lb/ft. y2.24 t·ha–1 = 1.0 ton/acre. xT-1 = 192 L (51 gal), T-2 = 96 L (25 gal), T-3 = 48 L (13 gal). wWithin a column, means followed by the same letter are not significantly different at the 5% level using Tukeys multiple comparison test.

Table 3. Irrigation effects on 1997 ‘Cabernet Sauvignon’ harvest juice composi- from rainfall) may have contributed to tion. the slight increase in fruit weight per vine, and resulted in similar yields re- Total corded between T-1 and T-2. soluble Titratable PRUNING WEIGHT, CROP LOAD AND z solids acidity VINE BALANCE. –1 y The highest irrigation Treatment (%) pH (g·L ) treatment (T-1) had the greatest prun- T-1 22.3 bx 3.02 ab 8.6 a ing weights at 1.0 kg/vine (2.3 lb/ T-2 21.7 b 2.99 a 8.9 a vine), followed by T-2 and T-3 at 0.7 T-3 20.2 a 3.08 b 7.4 a (1.5 lb/vine) and 0.5 kg/vine(1.2 lb/ vine), respectively (Table 2). Well bal- zTotal soluble solids are expressed as percent sucrose in g/100 mL of solution. y1.0 g·L–1 = 1000 ppm. anced vines should have pruning xWithin a column, means followed by the same letter are not significantly different at the 5% level using Tukeys weights ranging from 0.3 to 0.6 kg·m– multiple comparison test. 1 (0.2 to 0.4 lb/ft) of canopy (Coombe and Dry, 1992). Vines from T-1 had by irrigation treatments. These results 3.6 kg/vine (8 lb/vine), which corre- pruning weights of 1.0 kg·m–1 (0.4 lb/ agree with previous studies (Evans et sponds to an estimated yield of 8.5 ft)of canopy indicating a high-vigor al., 1993; McCarthy and t·ha–1 (3.8 t/acre). T-2 averaged a condition. Visual observation of these Coombe,1984; Bravdo et al., 1985; higher cluster weight/vine than T-1, vines during the growing season con- Smart and Coombe, 1983 and but the difference was not significant; firmed these results, and showed ex- Wample, 1997) demonstrating reduc- consequently the yields were nearly cessive canopy density. This particular tions in shoot and fruit growth. Previ- equivalent (12.5 t·ha–1 (5.6 t/acre) in situation may create shading problems ous work by Wample (1997) has shown T-2 vs. 11.6 t·ha–1 (5.2 t/acre) in T-1). and produce low fruit quality; thus that visible differences in shoot reduc- It is evident that the lowest irrigation vines of T-1 are considered to be out- tion would not normally be mani- rate (T-3) negatively affected the yield. of-balance. Crop load is another way fested until after full bloom, but this T-2 produced a similar yield to T-1, to quantify whether there is a balance was not true in this study. although it received half the amount of between vegetative growth and crop YIELD COMPONENTS. At harvest clus- water. This may suggest that with a yield. Smart and Robinson (1991) ter weight in T-1 was the greatest, but moderate irrigation reduction, yields show that crop load values between 5 not significantly different from T-2 are not affected. It should be noted, and 10 are optimal and below 5 indi- (Table 2). T-3 had the lowest cluster however, that soil moisture of T-2 cate excessive vegetative growth in re- weight. Similar results were observed were nearly as high as T-1, ≈10 d after lation to crop weight. It is concluded with berry weights (Table 2). The fruit veraison, 21 August through harvest that due to excessive canopy vigor and weight per vine was the least in T-3 at (Fig.1). This extra moisture (probably the poor crop load value of T-1 (4.8),

Table 4. Irrigation effects on 1997 ‘Cabernet Sauvignon’ wine compositionz and wine colory.

Titratable acidity Color Absorbency Absorbency Treatmentw (g·L–1)x pH density 520 nm 420 nm T-1 7.0 av 3.53 b 6.41 a 3.74 a 2.67 a T-2 7.1 a 3.49 b 7.41 b 4.37 b 3.04 b T-3 7.9 b 3.43 a 8.70 c 5.21 c 3.50 c zWine lots not replicated, three separate samples from each treatment were analyzed. yColor is based on light absorbency at the 420 and 520 nm wavelengths. x1.0 g·L–1 = 1000 ppm. wT-1 = 192 L (51 gal), T-2 = 96 L (25 gal), T-3 = 48 L (13 gal). vWithin a column, means followed by the same letter are not significantly different at the 5% level using Tukeys multiple comparison test.

166 ● January–March 2000 10(1) bency at industry standards of 420 and Table 5. Irrigation effects on ‘Cabernet Sauvignon’ cold hardiness (T50)z and water content (WC) measured on 3 Nov. 1997. 520 nm wavelength with T-3 having the darkest (highest absorbency) col- T50 Bud T50 Cane WC-Bud WC-Cane ored wine (Table 4). This color en- Treatmentx (°C) (°C) (%) (%) hancement observed in T-3 from a

w winemaker’s view was a positive effect T-1 –18.3 a –18.1 a 29.9 a 42.0 a but should not be the only consider- T-2 –17.1 a –17.3 a 27.9 a 42.2 a ation to vineyard irrigation strategies. T-3 –17.7 a –17.8 a 27.6 a 42.5 a COLD HARDINESS AND WATER CON- zT50 is the lowest temperature at which 50% of the population survives. 0F = 1.8(0C) + 32. TENT. Bud and cane tissues for each xT-1 = 192 L (51 gal), T-2 = 96 L (25 gal), T-3 = 48 L (13 gal). treatment were subjected to freezing wWithin a column, means followed by the same letter are not significantly different at the 5% level using Tukeys multiple comparison test. tests and analyzed for water content on three dates, 3 November 1997, 3 the irrigation rate is too high at 192 L/ and juice compositions determined 10 December 1997, and 9 January 1998. vine (51 gal/vine) per week, especially d earlier than anticipated. Although Differences among irrigation treat- early in the season. fruit maturity levels indicate slightly ments in cold hardiness and water con- T-2 had 0.4 kg (0.9 lb) of pruning underripe fruit, juice composition lev- tent of bud and cane tissues were not weight per meter of canopy which is els were showing significant differences observed on any of the three sampling within the optimum vegetative growth among treatments (Table 3). Signifi- dates. Only data of November sam- range. The crop load value of 7.4 for cant differences in % total soluble sol- pling are shown in Table 5. It is con- T-2, was also within the optimum ids (TSS) and juice pH were observed. cluded that with these irrigation treat- range and indicates a good balance Titratable acidities at harvest were simi- ments, cold hardiness of buds and between the canopy size and the crop lar among treatments. Previous stud- canes was not negatively affected. A that it supports. It was concluded that ies (Wample, 1997; Bravdo, et al., previous study by Wample (1997) the medium irrigation treatment of 96 1985; McCarthy and Coombe, 1984; found similar results. L/vine (25 gal/vine) per week pro- McCarthy, et al., 1987) have shown SOLUBLE CARBOHYDRATES IN CANE vided the best balanced vines with opti- that late season reductions in irriga- CORTICAL TISSUES. The accumulation mum fruit to wood ratio. The pruning tion can slightly increase sugar (TSS) of the soluble sugars (glucose, fruc- weight per meter of canopy for T-3 was levels at harvest which was not ob- tose, sucrose, raffinose and stachy- the least at 0.3 kg (0.7 lb), but within served in this study. T-3 TSS levels of ose) in the internode stem tissue was the acceptable range. The T-3 crop load 20.2 were significantly lower than ei- measured and analyzed for treatment value of 7.2 was also within the accept- ther T-1 or T-2. It is likely the vines differences over the same sampling able range. Although these numbers underwent severe water stress causing dates as above. Significant differ- lead to the conclusion of somewhat a physiological adjustment that result- ences between treatments were not balanced vines, other considerations ing in stomatal closure. This would observed for any of the sugars ana- should be taken into account. In fact, have led to reduced photosynthesis lyzed on each date (Table 6). How- field observations have indicated that T- and decreased levels of soluble sugars. ever, the concentration of each sugar 3 vines were severely water stressed to WINE COMPOSITION AND COLOR. increased from November to Janu- the extent that fruit shriveled during the were made from each treatment ary with all treatments (Table 6). ripening stage in mid-August. There- with standard industry procedures as This accumulation of soluble sugars fore, an irrigation rate of 48 L/vine (13 described by Margalit (1990) and aged during the midwinter season is not a gal/vine) per week is not recommended in glass carboys without oak addition. response to irrigation treatments, but under these conditions. The wines were sulphited with 40 a physiological response to low tem- JUICE COMPOSITIONS. –1 Juice com- mg·L (ppm) of K2S2O5 and racked perature as concluded by Hamman positions at harvest were analyzed and three times. The wines were analyzed et al. (1996). Since irrigation treat- differences were observed. To facili- for TA, pH and wine color. The irriga- ments did not affect cold hardiness it tate Canyon Wind’s harvest opera- tion treatments influenced wine TA, is unlikely that they would affect tions, all treatments were harvested pH, color density and color absor- carbohydrate accumulation.

Table 6. Irrigation effects on soluble sugar (10–5 m·g–1 of dry weight) of ‘Cabernet Sauvignon’ internode tissues from 1 November 1997 to 1 January 1998.z

November December January Treatmenty T-1 T-2 T-3 T-1 T-2 T-3 T-1 T-2 T-3 Glucose 4.8 4.8 5.5 10.0 10.7 9.5 15.6 12.9 13.9 Fructose 2.0 1.4 2.2 6.2 7.6 6.9 13.2 12.4 10.9 Sucrose 4.2 3.9 4.1 5.9 6.4 6.6 10.9 10.0 8.6 Raffinose 4.3 3.4 3.1 1.3 1.5 1.1 2.4 1.5 1.9 Stachyose 1.2 1.1 0.9 2.7 1.9 1.9 2.4 1.5 1.4 zOn each sampling date, no significant differences were observed between the three treatments for each sugar compared. Data are based on means of three replicates for each collection date. yT-1 = 192 L (51 gal), T-2 = 96 L (25 gal), T-3 = 48 L (13 gal).

● January–March 2000 10(1) 167 RESEARCH REPORTS

Conclusions Irrigation scheduling. 1989. Div. Agr. and Literature cited Natural Resources. Univ. of Calif. Publ. Several significant observations 21454. were made in this study. First, it is Bittenbender, H.C. and Gordon S. Howell, Jr. 1974. Adaptation of the spearman- Jackson, D. I. and P. B. Lombard. 1993. possible to control the canopy devel- karber method for estimating the T of opment of grapevines by irrigation 50 Environmental and management practices cold stressed flower buds. J. Amer. Soc. affecting grape composition and wine qual- management. It was found that for Hort. Sci. 99:187–190. this particular soil and site, the rate of ity—A review. Amer. J. Enol. Viticult. 44:409–430. 96 L/vine (25 gal/vine) per week Bravdo, B., Y. Hepner, C. Loinger, S. imposed until veraison (12 August), Cohen, and H. Tabacaman. 1985. Effect Kliewer, W. M., B. M. Freeman, and C. of crop level and crop load on growth, Hossom. 1983. Effect of irrigation, crop then reduced by 25% through harvest, yield, must and wine composition and provided the best balanced vines with level and potassium fertilization on quality of Cabernet Sauvignon. Amer. J. Carignane vines.I. Degree of water stress good canopy size, good yields, and Enol. Viticult. 35:247–252. excellent fruit and wine quality. Grow- and effect on growth and yield. Amer. J. Enol. Viticult. 34:186–196. ers should realize that these rates may Bravdo, B., and Y. Hepner. 1986. Irriga- change at other sites with different soil tion management and fertigation to opti- Margalit, Y. 1990. technology and mize grape composition and vine perfor- operations. The Wine Appreciation Guild. characteristics and conditions. mance. HortScience 21(3):328 (1600). In practice, rates should be modified San Francisco. according to the stage of development Coombe, B.G. and P. R. Dry. 1992. McCarthy, M. G. and B. G. Coombe. of grapevines and their seasonal water Viticulture. Vol. 2 Practices. Winetitles, 1984. Water status and wine grape quality. requirements. Second, cold hardiness Underdale, . Acta Hort. 171:447–56. of buds and canes was not affected by Evans, R. G., S. E. Spayd, R. L Wample, McCarthy, M. G., R. M.. Cirami, and D. the imposed irrigation treatments. This and M.W. Kroger. 1990. Water require- G. Furkaliev. 1987. The effect of crop load implies that irrigation strategies could ments of Vitis vinifera . Proc. 3rd and vegetative growth control on wine be used in Colorado for fruit Natl. Irr. Symp. Amer. Soc. Agr. Eng. quality. Proc. 6th Australian. Wine Ind. quality control without compromis- 154–161. Tech. Conf., Adelaide. p. 75–77 ing cold hardiness. Cold hardiness is Evans, R.G., S.E. Spayd, R.L. Wample, an important factor to consider in this Porter, M. 1996. Deficit irrigation in theory M.W. Kroeger and M.O. Mahan. 1993. and practice. Practical Winery and Vine- area due to the likelihood of winter Water use of Vitis vinifera grapes in Wash- yard July/August. p. 43–48. injury. In addition, treatments with ington. Agr. Water Mgt. 23:109–124. Smart, R.E. and B.G. Coombe. 1983. reduced irrigation were observed to Freeman, B.M., and W. M. Kliewer. 1983. have early cane maturity, thus less sus- Water relations in grapevines. p. 137–196. Effect of irrigation, crop level, and potas- In: T.T. Kozlowski (ed.) Water deficits and ceptibility to early fall . Third, sium fertilization on Carignane vines. II. carbohydrate reserves in canes were growth. Vol. VII. Additional woody Grapes and wine quality. Amer. J. Enol. crop . Academic Press. . not affected by irrigation treatments. Viticult. 34:197–207. Therefore, reducing irrigation would Smart, R.E. 1985. Principles of grapevine Gomez, K.A. and A.A. Gomez. 1984. Sta- not compromise carbohydrate storage canopy manipulation with tistical procedures for agricultural research. implications for yield and quality. A re- or accumulation which is essential for 2nd ed. Wiley, New York. cold hardiness. view. Amer. J. Enol. Viticult. 36:230–239. Other advantages of reduced irri- Hamman, R. grape harvest Smart, R. and M. Robinson. 1991. Sun- gation treatments are savings in cost of summary, 1996. Wines & Vines, March light into wine. Winetitles, Underdale, labor and materials associated with 1997 p. 36. Australia. trellis modification and vineyard man- Hamman, R.A. Jr., I.E. Dami, T.M. Walsh Somers, T. C. and Michael E. Evans. 1997. agement practices such as irrigation, and C. Stushnoff. 1996. Seasonal carbohy- Spectral evaluation of young red wines: pesticide application, shoot and leaf drate changes and cold hardiness of equilibria, total phenolics, free removal, hedging, pruning, etc. It is and grapevines. Amer. and molecular SO2. J. Sci. Food Agr. 28: concluded that given the proper irri- J. Enol. Viticult. 47:31–36. 279–287. gation and vineyard management prac- Hamman, R.A. Jr. 1993. Wine grape per- Stergios, B.G. and G.S. Howell. 1973. tices, the canopy size of these‘Cabernet formance of 32 cultivars in western Colo- Evaluation of viability tests for cold stressed Sauvignon’ vines can be controlled rado, 1982–1986. Fruit Var. J. 47:59–63. plants. J. Amer. Soc. Hort. Sci. 98:325– and confined to the simple vertical Hepner, Y., and B. Bravdo. 1985. Effect of 30. shoot-position system without the need crop level and drip irrigation scheduling on for canopy division. Wample. R.L. 1997. When understanding the potassium status of Cabernet Sauvignon irrigation—Many things are to be consid- and Carignane vines and its influence on ered. Vineyard & Winery Mgt. Nov/Dec, must and wine composition and quality. p. 72–81. Amer. J. Enol. Viticult. 36:140–147.

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