Effect of Crop Level on Growth, Yield and Wine Quality of a High Yielding Carignane Vineyard

Transcription

1 Effect f Crp Level n Grwth, Yield and Wine Quality f a High Yielding Carignane Vineyard B. BRAVDO 1, Y. HEPNER 2, C. LOINGER 3 S. COHEN 4, and H. TABACMAN s Three crp levels were induced by cluster thinning in a high yielding Carignane vineyard. Reductin f cluster number frm abut 60 t 40 per vine did nt result in reductin f yield, since berry size and number per cluster were increased. Pruning weight f the thinned treatment was increased and s was the capacity f the vines. Further thinning t 20 clusters per vine reduced the yields since the increase in berry size and number was nt sufficient t cmpensate fr the reduced number f clusters. The yield t pruning weight rati was fund t be a gd measure fr crp lad. Crp lad reductin frm 19.6 t 12.0 kg fruit per kg prunings increased wine quality and a further reductin t 8 did nt. It was cncluded that crp lads abve 12 have cnspicius effects f vercrpping, i.e., reduced wine quality, clr quality and intensity and ttal ash, delayed maturatin, reduced rate f sugar accumulatin, must acid cncentratin at cmparable sugar cntent, prline and amin acids cntent, bud fertility, and pruning weight. In high yielding cultivars, the crp lad rati has a mre relevant effect n wine quality than the crp level as such. The intensificatin f Israel's vineyards due t the intrductin f drip fertigatin and virus free plant material has increased the danger f vercrpping, especially in highly prductive cultivars like Carignane. The effect f crp levels n the grwth f the vines and n the quality f the fruit and the wines was nt always fund t be cnsistent (8,12,13,15,23,24,26). Even within the same cultivar, higher crps were nt always assciated with lwer quality (15,16,22,24). It may well be that varius results reprted were incnsistent because crp level alne is an insufficient measure fr crpping. There is need fr a measure which will clearly define vercrpping, undercrpping, r nrmal crpping. Such a measure shuld be related t the capacity, a term which represents bth vegetative grwth and crp yield (27). Since capacity is expressed as the ttal weight f the vine, it is nt a practical measure fr field use. Leaf area t fruit weight rati was successfully used fr the study f crp lad effects n fruit quality (13,14,25). This als is an incnvenient measure fr practical use. Pruning brush weight was measured and reprted in several studies (7,10,17,24). This is an interesting measure, since it is crrelated with leaf area (17) and linked t the capacity due t the relatively high fertility f grapevines cmpared t ther fruit trees. When vines are prperly pruned, the brush weight shuld be prprtinal t the number f spurs and canes retained, and therefre t crp yield. We have suggested the emplyment f the weight rati f crp yield t prunings as a measure fr crp lad (2,3,9). Values f this rati were reprted in sme studies (8,15,28), but n attempt was made t analyze this data in terms f crp lad. High crp levels have been fund t delay sugar accumulatin in sme studies (2,3,9,22,24,27), but n effect was fund in thers (8,15). High crp levels reduced ttal titratable acidity when harvested at sugar cntents similar t lwer crps (2,9,10,22), but in ther reprts (8,15) n such effect was bserved. Wine clr was nt affected by crp levels (8,26), was reduced by high ~,2The Hebrew University f Jerusalem, Faculty f Agriculture, P. O. Bx 12, Rehvt, Israel ,4,5Israel Wine Institute, Rehvt, Israel. This research was supprted by the Eugene Sh~enburger Fundatin, The Hebrew University f Jerusalem. The authrs acknwledge the skilled technical assistance f Mrs. Nehama Bar and Mrs. Shshana Shalm. Manuscript submitted fr publicatin 18 February Am. J. Enl. Vitic., Vl. 35, N. 4, 1984 crp levels in Carignane but nt in Cabernet Sauvignn (2,9), r was even fund t increase in nnirrigated high crpped plts (15). Wine quality was fund t be reduced at high crp levels (2,7,9,10), but in ther studies n effect r even a psitive ne was reprted fr varius cultivars (2,9,27). A better ptential fr aging was fund in lw crpped Carignane and Grenache vines, althugh n quality differences were reprted (24). Linger and Safran (16) reprted that medium yields f Semilln prduced better wines than high and lw yields. Freeman et al. (8) fund n effect f crp level n the quality f Carignane wines. We have fund that high crp levels reduced wine quality f Carignane, but nt f Cabernet Sauvignn (2,3,9). It seems, therefre, that a better knwledge f the mechanism f crp level effect n wine quality is needed in rder t understand the reasns fr the different results reprted in literature. In this paper, we reprt the results f a six year experiment in which the effect f three levels f crpping n varius parameters f grwth and quality were studied. Materials and Methds A field experiment was cnducted n virus free Carignane grafted n 110R rtstck, at Mazkeret Batya in the castal plain f Israel during the years 1976 t The vineyard was planted in 1971 with 1630 vines per hectare ( m) n deep brwn t gray alluvial sil cntaining abut 50% clay, 25% silt, and 25% sand with 1 t 1.5% rganic matter in the upper layer and ph f 7.5 t 7.8. Water and fertilizers were applied by fur L/h drippers spaced 1.5 m apart n a single lateral per rw. Irrigatin was applied weekly and ttalled 200 mm per seasn, an average f 0.2 class A pan evapratin cefficient, and this in additin t 450 mm average winter rainfall. Ammnium nitrate and ptassium chlride were applied weekly thrughut April, ttalling 120 kg/ha N and 100 kg/ha K, respectively. Three crp lad treatments by cluster thinning were established immediately after blming as fllws: Treatment 1 (UT) - unthinned cntrl, abut 60 t 70 clusters per vine; Treatment 2 (MT) - mderately thinned, 40 clusters per vine retained; Treatment 3 (ST) - severely thinned, 20 clusters per vine retained. Each treatment

2 CROP LEVEL EFFECT ON CARIGNANE cnsisted f fur replicates in a randmized blck design, 10 vines per replicate. Each plt was harvested when the fruit sugar cntent reached 21.5 t 22.0 Brix. One hundred berries were peridically sampled fr berry weight and cmpsitin determinatin. The berries were crushed by a Waring blender, filtered thrugh cheese clth, and the resultant juice was used fr qualititative analyses. A ph meter was used fr determining the end pint f ttal acid titratin with NaOH at ph = 8.3. Abut 25 kg fruit per plt were sampled at harvest, and wine was made by standard minivinificatin techniques at the Israel Wine Institute. Ptassium f musts and wines was assayed after HC1 digestin (21), prline by clrimetry using ninhydrin reactin (18). Amin acids (AA) were quantified by AA analyzer, starch was measured as glucse after enzymatic hydrlysis (6), tannins as general plyphenls (19,20). Wine clr was tested clrimetrically as absrbance at 420 and 520 nm, clr intensity as sum f readings at 420 nm nm, and clr quality as the absrbance rati f 420/520 nm. The ttal extract was cmputed by deducting the density f water plus ethanl frm that f wine, reduced extract by a further deductin f wine sugar. Tartaric, malic, and lactic acids were determined by paper chrmatgraphy. Wine quality was expressed n a 0 t 20 tasting scre system (5), integrating clr, arma, taste, and harmny scres. The tasting was perfrmed by the regular panel f the Israel Wine Institute. The data were subjected t analysis f variance fllwed by multiple range test, accrding t Student-Newman-Keuls. Treatment means nt marked by a cmmn letter differ significantly at P = 0.05 in the Figures and Tables, unless stated therwise. Results Fruit yields f the unthinned (UT) and the mderately thinned (MT) treatments were almst identical in fur ut f the six experimental years, and nly in the first and fifth year was a higher yield btained in the UT treatment (Fig. 1). The smaller number f clusters in MT was largely cmpensated fr by the increase in the number f berries per cluster and their size (Table 1, Fig. 2). Severe cluster thinning (ST) yielded significantly less fruit than the ther tw treatments every year (Fig. 1), since the ~ARIGNANE '/. g kg WGHT 100 WGHT I00 BUNCHES LARGE BE~RRIES BUNCHES PER VINE AN LAGEN ( 4 ) ( 2 ) t / h t / h pints 100i a a a a a / / 5O CROP LEVEL TREATMENTS [-]1. CONTROL! BUNCHES/VINE J:;'] BUNCHES/VINE dys brix mi/g X b \ a i 14r-1 T a ~- T T --!!, ::7 GRAPE PRUNING YIELD WINE YIELD WGHT PRUNING QUALITY (6) (6) RATIO (6) Z..]6 210 g/i g/i g/l ]00 r a /a HARVEST MUST JUICE DATE SUGAR BERRY (6) (6) (3) mg/t m~q 5O 18 # CROP LEVEL: 6 ~ b # 12i O ~ C ~ ~ v ~J L l i i ~ 7-6 ~ X I _ J~. I _ ~ VINTAGE VINTAGE Fig. 1. Effect f crp levels induced by cluster thinning n annual yields, pruning weight and wine quality f Carignane vines. Treatment means nt marked by a cmmn letter differ significantly at P = ph TOTAL TARTARIC MALIC TITRAT ACID ACID (6) ACIDS (6) (6) (6) TAR/MAL POTASSIUM PROLINE ACIDS RATIO ( 4 ) (1) Fig. 2. Effect f crp levels induced by cluster thinning n sme grwth, yield, quality and cmpsitin parameters f Carignane (Multiannual means. Number f years is indicated in parenthesis. The highest mean presented as 100% and its abslute value appears abve the clumns). Statistics as in Fig. 1. Table 1. Effect f crp levels induced by cluster thinning n sme yield parameters f Carignane in Crp level treatment Yield Berry weight Bunch weight Bunch/vines Berries/bunch t/ha %2 g % g % n. % n. % UT (High Crp) a c a MT (Medium Crp) a b b ST (Lw Crp) b a c F significance 1 ** significance level f.05*,.01"*,.001"** nt cmputed + 2 relative t 100% levels in UT treatment 3 Numbers nt fllwed by a cmmn letter differ significantly. Am. J. Enl. Vitic., Vl. 35, N. 4, 1984

3 _ CROP LEVEL EFFECT ON CARIGNANE Table 2. Effect f crp levels induced by cluster thinning n amin acid cntent f Carignane must in AMINO ACIDS (mml/l) Crp level treatment glycine alanine valine isleucine leucine tyrsine arginine prline asperaginethrenine glutamine GLY ALA VAL ILE LEU TYR ARG PRO ASP THR GLU UT (High Crp) b a0.11 a0.14 b b0.88 MT (Medium Crp) a b0.07 a0.11 a a1.64 ST (Lw Crp) a c0.03 b0.07 a al.43 average F 8.42* *** 12.2"* 5.53* * S.E Statistics symbls as in Table 1. COLOI~ INTENSITY (O,D,) p. O. -- r,j (.~ b- ~jn COLOR QUALITY (Z,20/520 rtno.d.) p WINE MALIC ACID (il) WINE TARTARIC ACID (g/i) ~,,4 ~ O ~O O.-, O -4-4 (.0 Z WINE RED COLOR (O.O. 520 nm) ) -- ] ---[ 1 > _ ~r i, WINE TANNIN (mg/i) WINE LACTIC ACID (g/i) i f-- T-- i.! l 1 WINE TI M*L RATIO P ~Jn I r ~jn I._ / Fig. 3. Effect f crp levels induced by cluster thinning n the cntent f sme acids tannin and n the clr f the wines (annual averages). Statistics as in Fig I 1 1 I i J number and weight f berries nly partially cmpensated fr the reduced number f clusters (Table 1, Fig. 2). The larger clusters f the thinned treatments have already been bserved in the relative size f the anlagen in bud analysis carried ut in the winter prir t the 1979 seasn (Fig. 2). Mrever, the number f clusters per vine in the spring f 1982 prir t thinning was fund t be significantly higher in the MT and ST treatments than in the cntrl. The differences in pruning weights between the treatments were greater than in the crp yields and fluctuated in ppsite directins (Fig.l). Mrever, MT was clser t ST in pruning weight and clser t UT in yields thrughut the entire experimental perid. Crp lad, expressed as yield t pruning weight rati, was greatly affected by the crpping treatments (Fig. 1). The crp lad varied frm 16 t 27 in UT, frm 12 t 15 in MT, and frm 8 t 12 yield t pruning weight rati in the ST treatment (nt shwn). The quality f wines prduced frm the UT treatment was significantly inferir t that f the ther tw treatments (Figs. 1, 2). In this treatment, unlike the thers, seasns with the highest crp lads had the lwest wine quality, and vice versa (Fig. 1). Mderate thinning (MT) caused less fluctuatins in pruning weight, crp lad and wine quality than the unthinned (UT) and severely thinned (ST) treatments. Relative mean levels f varius parameters fr the entire six year perid are presented in Figures 2 and 5. Fruit thinning treatments reduced yields, crp lad (yield/pruning weight rati), juice/berry rati and advanced the harvest date (Fig. 2). Significant differences were btained between crp lad and harvest date in all the treatments. Crp yield was significantly lwer nly in ST, and pruning weight and wine quality nly in the UT treatment. Ttal titratable acids and prline in the must rse significantly with thinning, while tartaric, malic acids, and ptassium tended t rise (insignificant). N treatment effects n must sugar and ph were bserved (Fig. 2). The tartaric t malic acid rati tended t rise with the increase in crp lad. Am. J. Enl. Vitic., Vl. 35, N. 4, 1984

4 CROP LEVEL EFFECT ON CARIGNANE WINE ~3r~, t ' t T -- l C3 2 ~--, 0.~ [ ~ ab, u,j I 0 - b --~J 1 T t l t ~ 30 L.~, Cr ~ 25~ w20 b~.z 28 b L~.--. } b J 22 ' Fig. 4. Effect f crp levels induced by cluster thinning n sugar and extract cntent and sme acids f the wines (annual averages). Statistics as in Fig. 1. 6'- i r j rr t; 3[ t [ ' L t ~ i L 19" "78,9" CARIGNANE WINE ' 'I. g/i gll gj g I g/i 100 F el I ALCOHOL TOTAL VOLATILE Fb~D TAI:TIT~RIC TITRAT ACIDS ACIDS ACID ACIDS (5) (5) O.D. mg/i 100 a abb ] el 0 ph COLOR COLOR TANNIN (5) INTENSITY QUALITY (5) (5) (5) meq/i gll g/i g/i 0.0. O.O. 100 a a e/ AL.,'~,L.NE TOTAl. REDUCEJ~ "total Z.: 0 ASH AS~ z.~t RAC ~ EXTRACT nm i MALIC TIM,,L LACTIC ACIDS ACIDS (5) RATIO (5) 52O qm Fig. 5. Effect f crp levels induced by cluster thinning n the cmpsitin f wines (Six year averages except when number f years are indicated in parenthesis. See Fig. 2 fr additinal infrmatin). Statistics as in Fig. 1. ] The amin acid cntent in the must was fund t be lwer in high crp treatment UT, althugh significance was recrded nly fr glycine, tyrsine, and glutamic acid (Table 2). Leucine and isleucine were present in very lw cncentratins but increased with crp lad. The effects f cluster thinning n wine cmpsitin are presented in Figures 3, 4, and 5. Fixed acids and wine extracts were increased with thinning. Vlatile acids were high in the UT wines in tw years, but the five year average did nt vary significantly (Figs. 3 and 5). The exceptinally high vlatile acid cntent in 1980 cincides with the lw quality wine scre (Fig. 1). The UT wines tended t maintain a relatively high level f tartaric acid and a lw level f malic acid (Figs. 4 and 5), and this led t a relatively high rati f tartrates t malates + lactates. Malic and tartaric acids tended t decrease during the years, whereas clr intensity increased. The UT wines had pr clr intensities, particularly red clr, and their clr qualities were inferir (Figs. 4 and 5). The ST wines had a very high clr intensity and T/M+L acid rati in 1978 (Fig. 4), when they attained an exceptinally gd wine quality (Fig. 1). The MT wine parameters were less subjected t fluctuatins thrughut the years than UT and ST (Figs. 3 and 4). Treatment means fr the entire perid shw that UT wines had less fixed acids, clr intensities and extracts and tended t have less alchl, tannin, ash, red and yellw clr than wines frm the thinned treatments (Fig. 5). N effect f cluster thinning n the ph was bserved. Discussin The thinning f whle clusters immediately after blm caused a significant reductin in yields nly when tw thirds r mre f the clusters were remved (Figs. 1 Am. J. Enl. Vitic., Vl. 35, N. 4, 1984

5 CROP LEVEL EFFECT ON CARIGNANE m 251 and 2). The vines reacted t cluster thinning by an increase in berry size, number f clusters frmed, and the number f berries per cluster (Figs. 1 and 2, Table 1). It seems that in additin t the direct effect n berry size, there was an indirect and cumulative effect n fertility. This is supprted by the enlarged size f anlagen primrdia fund in micrscpe examinatin and by the tendency fr a greater number f cluster prductin by thinned vines than by unthinned nes (Fig. 2). Mrever, the increase in the number f clusters frmed exceeded the increase in the number f spurs left at pruning (nt shwn). In spite f the fact that the yields f MT were almst the same as f UT, the pruning weight in MT increased significantly, and the rati f crp yield t pruning weight decreased (Figs. 1 and 2). It appears, therefre, that the rati f crp yield t pruning weight rather than the yield level per se affected mst f the yield, grwth, and quality parameters presented in this paper. This is cnsistent with the results btained with leaf area t fruit rati experiments (11,12,14,27), and seems t be a mre practical and easier measure. Bth ratis well represent the crp lad, i.e., the fruit yield relative t the vegetative grwth f the vine. Pruning weight is a similar measure t leaf area, since bth were fund t be crrelated (11,14,17,23,27). The fact that cluster thinning reduced the crp lad withut reducing the fruit yield in MT als indicates that prbably mst f the negative effects f vercrpping ccur during early summer, when several imprtant physilgical functins, like linear sht grwth, phase 1 f berry grwth, and fruit bud differentiatin take place. The unthinned UT treatment was undubtedly vercrpped. This is cnfirmed by lw acid cntent at cmparable Brix levels, lw prline, lw ptassium cntent f the must and leaves, reduced grwth and yield levels and delayed ripening, as fund elsewhere (7,23,24). It is als reflected by the mirrr image curves f annual variatins in UT crp lad and wine quality (Fig. 1) which demnstrate the inverse relatins between them at this range f crp lad values. Such a relatinship is nt apparent when wine quality variatins are cmpared t variatins in yield and pruning weights. The reductin in crp lad frm abut 13 yield/pruning weight rati in MT t 10 in ST did nt imprve the average wine quality fr the six years. Sme very gd ST wines were btained in 1978 and 1981, but quality fluctuatins in this treatment were cnsiderable and n relatinship t crp lad fluctuatins was apparent (Fig. 1). This shws that ST was nt undercrpped. Its vigr, which was expressed in the 2.5 t/ha pruning weight, did nt cmpete with the clusters fr sugar accumulatin r cnsumptin. The larger juice cntent per gram f fruit in the vercrpped treatment UT (Fig. 2) is prbably due t thinner skin and fewer seeds than in the lw crp lad treatments, but this is nt certain. Amin acid cntent f the must was lw in the UT musts which prduced inferir wines, and this is cnsistent with the findings f thers (1) where higher amin acid cntents, especially arginine and prline, increased the fermentatin rate and prduced a mre intensive arma. Nevertheless, it cannt be cncluded that amin acid cntent is always crrelated with quality since it was fund that certain irrigatin treatments increased the amin acid cntent f must and reduced wine quality (2). The present study shws that crp lad is a dminant factr in prducing must and wine quality. A cmparisn with ther studies f crp level effect is pssible nly where pruning weight data were reprted. Carignane in Califrnia (15) attained a crp yield similar t that f the present experiment, abut 32 t/ha, in the unthinned treatment, but due t a wider spacing the capacity f the vines in their experiment was much higher and the crp lad much lwer. Plts yielded 30.6 kg/vine in their experiment, while urs yielded 19.4 kg/vine nly. Nevertheless, the unthinned UT in Mazkeret Batya, Israel, was vercrpped, and the crrespnding treatment C2 in Califrnia was nt. Cluster thinning reduced crp lad in the present experiment frm 19 t abut 12 and 10, and cnsequently many typical vercrpping phenmena were eliminated and wine quality imprved. When crp lad was reduced frm 6.7 t 4.6, wine quality was nt imprved, and ther typical vercrpping phenmena were nt cnspicuus (15). It appears that at lw crp lad values (belw 10), the crp yield level is nt a dminant factr fr wine quality. Van Zyl et al. (28) have raised yields f Chenin blanc in Suth Africa by abut 50 percent withut affecting the crp lad (which remained arund 7 t 8) and the wine quality. Kasimatis (10) shwed that when the crp lad f Zinfandel vines was reduced frm 14.3 and 10 t values belw 10 a cnsiderable increase in arma quality and taste intensity was recrded, but n differences in quality were btained at crp lads between 4.24 and 7.48, and this is similar t the results f Kliewer et al. (15). Fisher et al. (7) fund in de Chaunac vines that cluster thinning did nt change the yield level f 8.8 kg/vine, but increased vigr, reduced crp lad frm 11.2 t 6.9 and resulted in a superir fruit quality. Weaver et al. (24) fund n effect f vercrpping n wine quality f Carignane and Grenache in Califrnia. We have calculated their crp lad values t range between 4.5 t 13.2 and frm 2.2 t 7.9 yield/pruning weight rati in Carignane and Grenache, respectively. Mst f their figures, hwever, were belw 10 and are cmparable t the range in which we als did nt bserve any crp lad effects. Weaver and Pl (26) studied crpping level effects induced by pruning severities. The crp lad values (ur calculatins) fr Thmpsn seedless, Carignane, and Ribier were 3.7 t 8.8, 6.0 t 10.9, and 9.3 t 18.1, respectively. The authrs cncluded that all three cultivars were resistant t vercrpping since three years f vercrpping did nt weaken the vines. Nevertheless, characteristic symptms f vercrpping, like delayed maturatin, straggly clusters with small berries and reduced levels f carbhydrates in the rts were apparent. Accrding t ur scale f crp lad, nly Ribier was vercrpped. Unfrtunately, n wine was made frm these varieties, quality values are absent, and it is therefre difficult t estimate the effect f vercrpping in this case. Am. J. Enl. Vitic., Vl. 35, N. 4, 1984

6 252 m CROP LEVEL EFFECT ON CARIGNANE Cnclusins Crp yield level is nt a sufficiently gd measure fr vercrpping. The crp yield t pruning weight rati seems t be a mre reliable measure fr crpping effects. Overcrpping effects in Carignane start t appear at crp lad values abve 10 t 12 yield t pruning weight rati. The main effects are: reduced wine quality and clr; delayed maturatin; reduced titratable acids at cmparable Brix levels; reduced must prline cncentratins; increased juice per gram f fruit; and reduced vegetative grwth, expressed as pruning weight. Delayed maturatin due t slwing dwn f sugar accumulatin is a very sensitive measure fr crp level and appears als at lw crp lad ranges where wine quality is nt affected. Reduced titratable acid at ptimal r cmparable sugar cntent is a gd measure fr vercrpping. Literature Cited 1. Bell, A. A., C. S. Ough, and W. M. Kliewer. Effects n must and wine cmpsitin, rates f fermentatin and wine quality f nitrgen fertilizatin f Wtis vinifera var. Thmpsn Seedless grapevines. Am. J. Enl. Vitic. 30:124-9 (1979). 2. Bravd, B. Mdificatin de I'envirnment par I'irrigatin et la fumure sn effet sur la qualite du vin. In: XVlIle Cngres internatinal de la vigne et du vin de 10.I.V. (Capetwn) (1983). 3. Bravd, B., Y. Hepner, C. Linger, S. Chen, and H. Tabacman. Effet de I'irrigatin et de I'alimentatin minerale sur la qualite de mut et des vins prvenant des vignbles de Cabernet Sauvignn et de Carignan aux rendements eleves en Israel. XVllle Cngres internatinale de la vigne et du vin de OIV, Le Cap : (1983). 4. Buttrse, M. S. Effect f reducing leaf area n the grwth f rts, stems and berries f Grd grapevines. Vitis 5: (1966). 5. Cnference Permanente de Chambres de Cmmerce Francaises & Italiennes des Regins Frntreres. Grenble, France (1973). 6. Fairbairn, N.J. Chemistry and Industry (Lndn), 86. In: Official Methds f Analysis f the Assciatin f Analytical Chemists. W. Hrwith, (Ed.) Washingtn AOAC 1975 (1953). 7. Fisher, K. H., O. A. Bradt, J. Wiebe, and V. A. Kirks. Cluster thinning "de Chaunac" French hybrid grapes imprves vine vigr and fruit quality in Ontari. J. Am. Sc. Hrt. Sci. 102:162-5 (1977). 8. Freeman, B. M., and W. M. Kliewer. Effect f irrigatin, crp level and ptassium fertilizatin n Carignane vines. II. Grape and wine quality. Am. J. Enl. Vitic. 34: (1983). 9. Hepner, Y. The effect f crp lad and cultural practices n the quality f the fruit and the vine f high yielding vineyards. Ph. D. Thesis, The Hebrew Univ. f Jerusalem. (Hebrew, English summary) (1983). 10. Kasimatis, A. N. Differential crpping levels f Zinfandel vines - a prgress reprt n sme effects n vine grwth, fruit cmpsitin and wine quality. Internat. Symp. n Quality f Vintage, Capetwn. pp (1977). 11. Kliewer, W. M., and A. J. Antcliff. Influence f defliatin, leaf darkening and cluster shading n the grwth and cmpsitin f Sultana grapes. Am. J. Enl. Vitic. 21:26-36 (1970). 12. Kliewer, W. M. Effect f time and severity f defliatin n grwth and cmpsitin f Thmpsn Seedless grapes. Am. J. Enl. Vitic. 21:37-47 (1970). 13. Kliewer, W. M., and R. J. Weaver. Effect f crp level and leaf area n the grwth, cmpsitin and clratin f Tkay grapes. Am. J. Enl. Vitic. 22:172-7 (1971). 14. Kliewer, W. M., and R. D. Fuller. Effect f time and severity f defliatin n grwth f rts, trunk and shts f "Thmpsn Seedless" grapevines. Am. J. Enl. Vitic. 24:59-64 (1973). 15. Kliewer, W. M., B. M. Freeman, and C. Hssm. Effect f irrigatin, crp level and ptassium fertilizatin n Carignane vines. I. Degree f water stress and effect n grwth and yield. Am. J. Enl. Vitic. 34: (1983). 16. Linger, C., and B. Safran. Interdependence entre le rendement, la maturatin des raisins et la qualite des vins. Ann. Technl. Agric. 20: (1971 ). 17. Ough, C. S., L. A. Lider, and J. A. Ck. Rtstck-scin interactins cncerning wine making. I. Juice cmpsitn and effects n fermentatin rate with St. Gerge and 99-R rtstcks at tw nitrgen fertilizer levels. Am. J. Enl. Vitic. 19: (1968). 18. Ough, C. S. Rapid determinatin f prline in grapes and wine. J. Fd Sci. 34: (1969). 19. Pr, M. J. Reprt n the spectrphtmetric determinatin f tannin in wines and whiskies. J. Assc. Agric. Chem. 35:255-7 (1952). 20. Pr, M. J. Spectrphtmetric determinatin f tannins in wines and spirits. J. Assc. Agric. Chem. 37:665-6 (1954). 21. Rs, J. T. H., and W. J. Price. Analysis f fruit juice by atmic absrptin spectrphtmetry. II. Direct determinatin f several majr and trace metals. J. Sci. Fd Agric. 21:51-2 (1970). 22. Safran, B. Effects f cultivatin practices n the quality f the vintage in ht regins. Internat. Symp. n Quality f Vintage. Capetwn. pp (1977). 23. Weaver, R. J., and S. B. McCune. Effects f vercrpping Alicante Buschet grapevines in relatin t carbhydrate nutritin and develpment f the vine. Prc. Am. Sc. Hrt. Sci.75: (1960). 24. Weaver, R. J., S. B. McCune, and M. A. Amerine. Effect f level f crp n vine behavir and wine cmpsitin in Carignane and Grenache grapes. Am. J. Enl. Vitic. 12: (1961). 25. Weaver, R. J. Effects f leaf t fruit rati n fruit quality and sht develpment f Carignane and Zinfandel grapevines. Am. J. Enl. Vitic. 14:1-12 (1963). 26. Weaver, R. J., and R. M. Pl. Effect f varius levels f crpping n behavir f Vitis vinifera grapevines. Am. J. Enl. Vitic. 19: (1968). 27. Winkler, A. J., J. A. Ck, W. M. Kliewer, and L. A. Lider. General Viticulture. Univ. Calif. Press, Berkeley, (1974). 28. Van Zyl, J. L., and A. W. Weber. Irrigatin f Chenin blanc in the Stellenbsch area within the framewrk f the climate-silwater-plant cntinuum. Internat. Symp. n Quality f Vintage. Capetwn. pp (1977). Am. J. Enl. Vitic., Vl. 35, N. 4, 1984