36 Plant Spacing Effects on Canopy Characteristics, Wine Quality and Labour

Transcription

1 Plant Spacing Implicatins fr Grafted Grapevine II. Sil Water, Plant Water Relatins, Canpy Physilgy, Vegetative and Reprductive Characteristics, Grape Cmpsitin, Wine Quality and Labur Requirements J.J. Hunter ARC-Fruit, Vine and Wine Research Institute, Nietvrbij Centre fr Vine and Wine, Agricultural Research Cuncil, Private Bag X526, 7599 Stellenbsch, Suth Africa Submitted fr publicatin: March 1998 Accepted fr publicatin: Octber 1998 Key wrds: Vitis vinifera, Pint nir, grapevine, plant spacing, water relatins, canpy, vegetative grwth, reprductive grwth, wine quality, labur Results presented in part at the First Suth African Sciety fr Enlgy and Viticulture Internatinal Cngress, Cape Twn, Suth Africa, 1995, the Furth American Sciety fr Enlgy and Viticulture Internatinal Sympsium n Cl-Climate Viticulture and Enlgy, Rchester, USA, 1996, and the Fifth Office Internatinal de la Vigne et du Vin Internatinal Sympsium n Grapevine Physilgy, Jerusalem, Israel, Vitis vinifera L. cv. Pint nir vines grafted nt rtstck 99 Richter and grwn under six plant spacings (3 x 3 m; 3 x 1,5 m; 2 x 2 m; 2 x 1 m; 1 x 1 m; 1 x,5 m) were investigated in terms f canpy dimensin and micrclimate, sil cnditins, canpy physilgy, vegetative and reprductive grwth characteristics, grape cmpsitin, wine' quality and labur input. Vines were pruned t six buds/m2 sil surface and supplementary irrigated just after pea berry size and veraisn stages. The number f leaf layers, light intensity and air flw generally decreased with clser spacing, whereas relative humidity increased. In cntrast t the virtually stable, albeit lwer, sil water cntent f clser-spaced vines, that f wider spacings nticeably decreased frm veraisn t ripeness. This may be ascribed t the almst cntinuus seasnal shading f the sil in the case f the narrwer spacings, and the generally higher sil temperatures fund fr the wider spacings. Leaf and bunch water ptentials f bth wider- and clser-spaced vines decreased during the ripening perid. Bunches were mre sensitive t water stress. Leaf and bunch water ptential cincided with sil water cntent. The lwer phtsynthetic activity f clsely spaced vines was accmpanied by increased transpiratinal water lss and is mainly ascribed t less favurable canpy micrclimate. Despite the supplementary irrigatin and slight differences in leaf water ptential between spacings, wider-spaced vines apparently grew under less water stress during the ripening perid. This was als evident frm leaf xylem sap abscisic acid levels at ripeness. Sht, leaf and berry grwth rates apparently increased with narrwer spacing, whereas ttal leaf area per vine decreased. Fresh berry mass f narrw-spaced vines was, hwever, slightly lwer at ripeness. Budding f narrw spacings increased, whereas fertility and bunch mass were reduced, resulting in decreased yield per vine. Optimum berry set and yield per hectare ccurred fr medium-spaced vines (2 x 2 m, 2 x 1 m); this was als evident n a m2 sil surface basis. Leaf area per fresh mass f widely spaced vines ( 3 x 3 m, 3 x 1,5 m) was much lwer than the generally required 1-12 cm2 and pints t vercrpping. Musts f widely spaced vines had less sluble slids and titratable acidity, whereas must ph increased prgressively frm widely t clsely spaced vines. It wuld seem that widely spaced vines were vercrpped due t lw cultivar vigur and/r lw yielding capacity f the sil, eventually affecting ripening. Grapes frm medium-spaced vines had higher anthcyanin levels in the skin. Sensrially, wines made frm clser spacings (2 x 2 m, 2 x 1 m, 1 x 1 m, 1 x,5 m) scred distinc Iy higher than thse frm widely spaced vines. Althugh yield per hectare was higher, clsely spaced vines (1 x 1 m, 1 x,5 m) needed significantly higher inputs fr canpy management, harvesting and pruning. Cnsidering land utilisatin, vine perfrmance, wine quality as well as labur input, medium-spaced vines (2 x 2 m; 2 x 1 m) perfrmed ptimally. It is generally accepted that the spacing f grapevines may have far-reaching implicatins fr physilgical, vegetative and reprductive perfrmance, grape cmpsitin, and eventually wine quality (Archer & Strauss, 199 and references therein; Reynlds, Wardle & Naylr, 1995). Althugh the chice f a plant spacing may initially be dependent n sil physical and chemical prperties, the shape and size f fliage walls, and in particular the number, distributin and expsure f individual leaves, will ultimately als dictate the extent t which a chsen spacing will meet yield and quality requirements (Smart, 1973; Shaulis, 198). Alng with Acknwledgements: Technical assistance by G.W Fuche, DJ. Ie Raux, e.g. Vlschenk, AJ. Heyns. E. Burger, H.e. Strauss, WJ. Hendricks, L.M. Paulse, E. Rhde and L.F. Adams as well as financial supprt by the Suth African Vine and Wine Industry thrugh Winetech are greatly appreciated. The Department f Bichemistry, University f Stellenhsch, is thanked fr determinatin f ahscisic acid cncentratins. 35

2 36 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur training and trellising system, plant spacing has prved t be an effective tl in the accmmdatin f vigur thrugh an increase in crdn/canpy length, which imprves bth leaf and fruit micrclimate and enhances the even ripening f fruit (Shaulis, 198; Smart, 1985; Reynlds et ai" 1995). Studies under dry1and (Archer & Strauss, 1985, 1989, 199) and irrigated (Reynlds et al., 1995; Hunter, 1998) cnditins shwed that plant spacing impacts directly n majr physilgical prcesses and is crucial in the ptimal utilisatin f available sil vlume and slar energy. Sil water depletin was fund t be a very imprtant regulatr f plant perfrmance, particularly under high planting densities. A reductin in water supply was assciated with a decrease in phtsynthetic rate (Rdriques et al., 1993; Nar, Bravd & Gelbter, 1994; Nar & Wample, 1994), an inhibitin in sht elngatin (Hfacker, 1977; Van Zyl, 1984; Nar & Wample, 1996) and leaf expansin (Schultz & Matthews, 1993), and berry cntractin during the pre-veraisn phase (Greenspan, Shackel & Matthews, 1994). Furthermre, dense canpies are created when the number f shts and the rati f sht grwth t available sil and spatial grwth vlume are t high. This was shwn t result in interir-canpy shade (Smart, 1985), which is detrimental t phtsynthetic activity (Hunter & Visser, 1988), yield, grape cmpsitin and wine quality (Smart et al., 1985; Hunter et al., 1995). On the ther hand, available land resurces will be under-explited and sub-ecnmic end-prduct btained when lw vigur is accmmdated in excessive grwth vlumes. Crrect plant spacing is therefre f the utmst imprtance t ensure the utilisatin f sil vlume t such an extent that the best pssible ecnmic benefit can be btained in terms f yield, grape and wine quality, and labur input. In an accmpanying paper the effect f plant spacing n abvegrund and subterranean grwth, dry matter partitining, and dry matter cmpsitin was reprted (Hunter, 1998). In this paper, the physilgical, vegetative and reprductive respnse f a mature, supplementary irrigated Vitis vinifera L. cv. Pint nir/99 Richter vineyard t different plant spacings n a mediumptential sil is addressed. Effects n sil and plant water relatins, wine quality and labur required fr pruning, harvesting and canpy management practices are als reprted. MATERIALS AND METHODS Vineyard and treatments: A l4-year-ld Vitis vinifera L. cv. Pint nir (clne BKV)/99 Richter (clne 1/3/1) vineyard n a Glenrsa sil (Sil Classificatin Wrking Grup, 1991) was used. Befre the vines were established, the sil was deep delved in tw directins t a depth f 1 m using a wing plugh. The vines were planted in an East-West directin and spaced (betweenrw/in-rw) 3, x 3, m, 3, x 1,5 m, 2, x 2, m, 2, x 1, m, 1, x 1, m, 1, x,5 m. They were trained t a five-strand hedge and spur pruned t six buds/m2 sil surface area. Over the last five years f the experiment, supplementary irrigatin (5 mm) was applied just after pea size and veraisn stages, respectively (dryland prir t that - Archer & Strauss, 1985). A cver crp (rye) was swed between the rws in autumn and killed with a herbicide befre bud break. The treatments and five replicates were cmpletely randmised (Hunter, 1998). Measurements: Sil cnditins: Sil water was measured gravimetrically at three sil depths ( - 3 cm; 3-6 cm; 6-9 cm) and at fur develpmental stages (berry set; pea berry size; veraisn; ripeness). Sil temperature was measured weekly frm veraisn by means f a data-lgger. Canpy physilgy: Phtsynthetic activity (mg CO2/dm2/h) and rate f transpiratin (J.l g H2/cm2/s) f basal leaves just abve the bunch zne were measured frm mid-mrning until midday using a prtable phtsynthesis meter (ADC) as described by Hunter & Visser (1988). Three leaves were measured per replicate. Leaf and bunch water ptential were determined frm early afternn until mid-afternn using a Schlander pressure chamber (Schlander et al., 1965). Mature leaves fully expsed t the sun were excised frm just abve the bunch zne. Leaf petiles and bunch stems were re-cut with a scalpel befre insertin int the chamber within ne minute f remval f leaveslbunches. Three leaves were remved per replicate. Exudate pressed frm the leaves was cllected with a pasteur pipette and the physilgically active 2-cis-(S)-frm f the endgenus plant grwth regulatr, abscisic acid, determined by means f a mnclnal antibdy radiimmunassay technique (Mertens, Deus-Neumann & Weiler, 1983). The exudate was assumed t be representative f xylem sap (cf. als Lang & During, 1991). Canpy dimensin and micrclimate: The number f leaf layers and canpy width were determined just abve the bunch zne accrding t the pint quadrat principle f Smart et al. (1985) whereby a thin steel rd is passed hrizntally thrugh the canpy and the number f leaves cntacted and the width f the canpy recrded. Five canpies were measured n a randm basis per replicate and three randm passes made per canpy. Phtsynthetically active radiatin was measured using ali-cr Line Quantum Sensr frm mid-mrning inside as well as utside the canpy and results expressed as % f ambient. Air flw and temperature inside the canpy were measured using a Kane-May 43 therm anemmeter and relative humidity with a Kane-May 8 humidity meter. All micrclimate measurements were taken just abve the bunch zne. Three canpies were measured per replicate. Physilgical and micrclimate measurements in the canpy were cnducted n the same day and at the different develpmental stages mentined abve. In rder t determine the vine-spacing effect n shading f between-rw sil, and adjacent and ppsite vines, shade patterns f representative canpies f the different treatments were measured hurly frm 8: until 16:3 at the different develpmental stages. Vegetative characteristics: Main sht length was measured weekly frm budding n ne vine per replicate. Ttal leaf area per sht was measured using ali-cr Li 31 area meter at the different develpmental stages; the number f leaves was als recrded. Reprductive characteristics: Fruitfulness (the number f bunches per number f shts riginating frm buds allcated during pruning) as well as budding percentage (number f shts/number f buds allcated during pruning x 1) were determined at S. Afr. J. Enl. Vitie., Vl. 19, N.2, 1998

3 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur 37 ripeness n all vines. The number f berries per bunch, bunch mass, and ttal yields were als determined. Fresh and dry (freeze-dried) berry mass were determined frtnightly frm pea berry size n ne sht per replicate. Grapes f all treatments were harvested n the same day. Grape cmpsitin: At ripeness, sluble slids, titratable acidity, and ph f the must were determined n a randm sample per replicate, accrding t standard ARC-Nietvrbij methds. Ttal anthcyanins f the ripe grape skin were analysed as reprted by Hunter, De Villiers & Watts (1991). Winemaking: Wines were made accrding t standard ARC Nietvrbij prcedures. Grapes f replicates 1 and 2, and thse f replicates 3,4 and 5, respectively, were cmbined. Wine quality: Wines were sensrially evaluated by a trained panel f 12 judges. The acceptability f the wine clur, acidity, hardness and bdy, as well as ttal arma intensity and verall wine quality were evaluated n a percentage basis. Labur input: The man hurs needed fr suckering (remval f shts nt lcated n spurs at 3 cm length), sht psitining (psitining f shts in line with spurs twice during the seasn), tpping (just after pea size f all shts grwing in excess f 3 cm abve the tp wire), harvesting and pruning were recrded. Statistics: Mean values f 1993/94 and 1994/95 seasns are presented. Significant differences were determined using Student's t-lsd test. RESULTS AND DISCUSSION Canpy dimensin and micrclimate: A general decrease in the number f leaf layers, light intensity and air flw in the canpy ccurred with clser plant spacing (Table 1). Relative humidity, hwever, increased with narrwer spacing. The micrclimate results can be attributed mainly t the physical betweenrw spacing. In the case f particularly clsely spaced vines (1 x 1 m; 1 x,5 m), canpy cnditins were mre favurable t the ccurrence f pests and diseases (Smart et al., 199; Stapletn & Grant, 1992; Duncan, Stapletn & Leavitt, 1995). This will inevitably lead t a mre intensive pest and disease cntrl strategy with greater financial and envirnmental implicatins, particularly fr grapert-sensitive cultivars and during years when cnditins fr disease develpment are ptimal. Sil cnditins and canpy physilgy: It is evident that sil water f wider-spaced treatments (3 x 3 m, 3 x 1,5 m, 2 x 2 m) nticeably decreased frm veraisn t ripeness, particularly in deeper sil layers, whereas that f clser-spaced treatments, albeit generally lwer, remained relatively stable (Fig. 1). This may partly be attributed t the generally higher sil temperatures f wide - versus clser-spaced vines (Fig. 2). The almst cntinuus shading f between-rw sil in clser plantings during the grwth seasn (Fig. 3) may als have prevented excessive evaptranspiratin and secured a base level f water. In spite f the abve, leaf and bunch water ptential f bth widely and clsely spaced vines decreased during the ripening perid, fluctuating mre r less in tandem with sil water cntent (Figs 4 & 5). Reasnably gd relatinships between leaf water ptential and sil water cntent f different sil layers were fund at veraisn (Fig. 6); at ripeness these relatinships were pr (Fig. 7). The ppsite situatin ccurred fr bunch water ptential (Figs 8 & 9). In all cases the prest relatinships were fund fr the shallwest sil layer ( - 3 cm). The relatinship between leaf and bunch water ptential was pr at veraisn, but reasnably gd at ripeness (Fig. 1). Prir t veraisn, n differences in water ptential were fund between spacings (data nt shwn). During the ripening perid differences in leaf water ptential were als slight, whereas differences in bunch water ptential were mre accentuated, particularly at ripeness (Figs 4 & 5). The leaf water ptential values f apprximately -8 kpa t -125 kpa fund in this study are higher than thse reprted by Archer & Strauss (199) under dry land cnditins ver the midday perid and wuld seem t indicate that the vines were nt severely waterstressed. The data nevertheless indicate that despite the supplementary irrigatin and slight differences in leaf water ptential between spacings, wider-spaced vines generally grew under less water stress than clsely spaced vines during the ripening perid (cf. als Archer & Strauss, 199). This is cnfirmed by the significantly higher abscisic acid levels that ccurred in the xylem sap f clsely spaced vines at ripeness (Fig. 11). Elevated levels f abscisic acid are knwn t be assciated with water limitatin and stmatal clsure (Lveys & Kriedemann, 1974). Given the slight differences in leaf water ptential (Fig. 4), the lwer light intensity, decreased air flw and higher humidity in the canpies f clser-spaced vines (Table 1) culd have largely cntributed t their decreased phtsynthetic activity (Fig. l2)(cf. als Hunter & Visser, 1988; Hunter et al., 1995). Althugh water stress has an bvius detrimental effect n phtsynthesis (cf. Liu et al., 1978; Rdriques et al., 1983; Nar et al., 1994; Nar & Wample, 1994), it can be reasned that that was nt the majr regulating mechanism in this case, but that phtsynthetic activity was primarily affected by canpy micrclimate. Phtsynthetic activity f clser-spaced vines (2 x 1 m; 1 x 1 m; 1 x,5 m) was accmpanied by prgressively increased transpiratinal water lss, which wuld have impacted directly n water relatins (Fig. 13). Gd relatinships between phtsynthetic activity and sil water cntent f different sil layers were fund at veraisn, but evidently nt at ripeness (Figs 14 & 15). The data cllectively indicate that leaf turgr f clsely spaced vines was largely maintained, despite the bvius physilgical stress experienced by these vines, as indicated by the decrease in bunch water ptential at ripeness (Fig. 5) and increase in leaf abscisic acid levels in particular (Fig. 11). It seems, therefre, that carbn assimilatin f vines in this study was largely independent f the smtic status f the leaf. Similar results were reprted by Rdrigues et al. (1993). It is als pssible that the effects f canpy micrclimate were highlighted by the mild water stress and vice versa. Accrding t Osri et al. (1995) mild water deficits have a marginal depressing effect n Phtsystem II phtchemical efficiency. The ccurrence f a higher density f particularly fine and extensin rts in the case f clser-spaced vines (Hunter, 1998), and therefre the pssibility f a larger amunt f grwth regula- S. Afr. J. Enl. Vitie., Vl. 19, N.2, 1998

4 38 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur trs in the xylem sap f these vines (Richards, 1983), culd als have affected the abvegrund respnse f the vines t envirnmental factrs and the extent f physilgical stress experienced, The higher rati f thin versus thick rts in the sil prfile f these vines mst likely increased the efficiency f the rt system t absrb water and withdraw nutrients frm a drying sil. It has been suggested that abscisic acid transprted frm the leaves t the rts may act as part f a system regulating water ptentials and i'n transprt frm the rts t the leaves (Cram & Pitman, 1972; Waltn, 198). Davies et at. (1986) als suggested that a decrease in water ptential arund individual rts, and thus rt tip turgr, may reduce the synthesis and transprt f cytkinins in the rts and that this, in cmbinatin with a reduced uptake f nutrients, may act as chemical signal in affecting the physilgy f the sht independently frm its hydraulic status. Vegetative and reprductive grwth characteristics: Sht elngatin rates have previusly been fund t be sensitive t different sil water regimes (Van Zyl, 1984). Under dryland cnditins, sht elngatin rates f clsely spaced Pint nir vines decreased during the last three weeks f ripening at afternn leaf water ptentials f -12 t -14 kpa (Archer & Strauss, 199). Nar & Wample (1996) fund internde grwth rates t be negatively crrelated with sht stem water ptential and suggested that a stem water ptential f -75 kpa can be cnsidered as threshld fr a decline in sht elngatin rate f Cncrd grapevines. In this study, afternn leaf water ptentials f up t -125 at ripeness (Fig. 4) did nt affect sht elngatin rates f clsely spaced vines (Fig. 16). In fact, sht elngatin rates f clser-spaced vines appeared higher than thse f wider-spaced vines. It therefre seems that the reactin f the vines may rather be ascribed t undercrpping r vercrpping f the respective treatments. A similar tendency ccurred fr leaf area per sht (Fig. 17) and area per leaf (Fig. 18); ttal leaf area/vine, hwever, still decreased with clser spacing (Fig. 19). Accrding t Patakas, Nitsakis & Stavrakas (1997) the cell wall elasticity f yung leaves enables vines t maintain a psitive pressure in cells, thereby sustaining enlargement and hence plant grwth under mild water stress cnditins. Furthermre, a decrease in water ptential f mature leaves may help t maintain water uptake frm drying sil. Evidently, the berries f clser-spaced treatments (2 x 2 m, 2 x 1 m, 1 x 1 m, 1 x,5 m) had cmparatively higher dry mass than thse f widely spaced treatments at least up t tw weeks befre ripeness (Fig. 2). At ripeness fresh berry mass f clser spacings (2 x 1 m, 1 x 1 m, 1 x,5 m) was slightly lwer (Fig. 21), crrespnding t their mre negative bunch water ptentials (Fig. 5). Given the fact that leaves and fruit cmpete fr water, a higher slid:water rati in the berry indicates mre efficient translcatin f assimilates t the berry, berry respnse t lwer vine water status and/r dehydratin f the berry, but may als pint t a mre favurable leaf area:fruit mass rati. Althugh mechanisms such as berry transpiratin, hydratin f the berry at a lwer rate than in "nn-stressed" vines, and xylem backflw frm the berry t the rest f the vine, resulting in berry cntractin, are recgnised as being invlved in the dehydratin f the berry, Greenspan et al. TABLE 1 Vine-spacing effect n canpy dimensin and micrclimate at ripeness. Spacing Number Canpy Light Air flw Relative Temperature (m) f leaf width (cm) intensity (% (cm/s) humidity (C) layers f ambient) (%) 3x3 36 ab 39 a 124 ab 26 a 33 b 35 a 3 xl,5 3,8 a 4 a 11 5 b 22 ab 35 ab 33 a 2x2 3,3 b 39 a 16,5 a 2 ab 33 b 35 a 2 xl 3,5 ab 37 a 9,5 b 2 ab 34 ab 34 a 1 x 1 3,3 ab 38 a 11,2 b 18 b 37 a 33 a 1 x,5 3,3 b 38 a 7,9 b 19 b 38 a 34 a Values in clumns fllwed by the same letter d nt differ significantly (p,5) TABLE 2 Vine-spacing effect n reprductive grwth parameters. Spacing Budding Fertility Berries Bunch Yield/ Yield Yield/m2 Leaf area (m) (%) index set/bunch mass VIlle (tlha) sil (cm2)/fresh (g) (kg) surface mass (g) grapes 3x3 79,44 c 1,98 a 83,35 b 19,2 a 1,34 a 11,49 c 1,15 7,84 3 x 1,5 91,66 bc 2,2 a 98,95 ab 123, a 5,76 b 12,81bc 1,28 7,14 2x2 12,78 bc 1,8 a 1,8 ab 17,2 a 5,55 b l3,88 b 1,39 8,53 2 x 1 11,68 b 1,86 a 18,95 a 114,75 a 2,78 c 13,92 b 1,39 9,7 1 x 1 172,8 a 1,76 a 96,5 ab 98,8 a 1,91 d 19,8 a 1,91 1,24 1 x,5 185,4 a 1,62 a 88,96 ab 99,8 a,88 e 17,6 a 1,76 19,46 Values in clumns fllwed by the same letter d nt differ significantly (p,5).

5 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur 39 (1994) suggested a lss in xylem cnductance t be the mre bvius explanatin during the pst-veraisn perid; this can t a certain extent be balanced by increased phlem cnductance. Nevertheless, since the clser-spaced vines in this study were nt unduly water-stressed during the pre-veraisn perid (data nt shwn) and the diurnal cntractin f pst veras in berries displayed a marked resistance t water deficit (Greenspan et ai., 1994), berry respnse at ripeness culd have been a nrmal reactin t inherently lwer vine water status. Cmpetitin fr water between the berries and the shts culd als have cntributed t a decline in water cntent f the berries f clser spacings. Shts cntinued t grw during this perid (Fig. 16). Althugh budding was significantly increased, fertility and bunch mass f clsely spaced vines ( 1 x 1 m, 1 x,5 m) were seemingly reduced, resulting in decreased yield per vine, and indicating that the vines were subjected t cumulative stress (Table 2). Yield per hectare still increased with clser spacing (Table 2). Hwever, at medium spacing, mre r less stable values ccurred, indicating ptimum yield per hectare fr mediumspaced vines (2 x 2 m, 2 x 1 m). This was als fund n a m2 sil surface basis and crrespnds t cane and rt mass as well as ttal vine dry mass results (Hunter, 1998). Leaf area/fresh mass f the widely spaced vines (3 x 3 m, 3 x 1,5 m) was much lwer than the 1-12 cm2 generally required t adequately ripen ne gram f fruit (Hunter & Visser, 199 and references therein) (Table 2) and again indicates that these vines were mst likely vercrpped under the cnditins f the experiment. Grape cmpsitin: Musts f widely spaced vines had less sluble slids and titratable acidity, whereas must ph increased prgressively frm widely t clsely spaced vines (Table 3). Cnsidering the differences in fresh berry mass between spacings (Fig. 21), it is evident that the lwer sluble slid cntents in musts f widely spaced vines cannt slely be ascribed t the slightly higher water status f the berries at ripeness. It wuld rather seem that, despite the generally better sil and plant water status, canpy micrclimate and phtsynthetic activity, the widely spaced vines were vercrpped; pssible reasns are inherently lw cultivar vigur, and/r lw yielding capacity f the sil, which resulted in these vines being unable t sufficiently supprt high vigur and crp lads under the cultural cnditins f the experiment, eventually leading t delayed ripening. Qualitatively, berries f clser spacings (2 x 2 m, 2 x 1 m, 1 x 1 m, 1 x,5 m) had higher anthcyanin cntents in the skin (Table 3). Despite their slightly lwer fresh mass, the quantitative anthcyanin cntent in the skin was als higher. Furthermre, since the skin t pulp rati is inversely related t berry size, clur extractin wuld increase during pressing f these grapes. This wuld be a big advantage in the case f Pint nir vinificatin in particular. Wine quality: Sensrial evaluatin f the acceptability f the clur, acidity, hardness and bdy as well as ttal arma intensity and verall quality shwed that the wines made frm grapes f clser-spaced vines (2 x 2 m, 2 x 1 m, 1 x 1 m, 1 x,5 m) were distinctly better than thse made frm grapes f widely spaced vines, irrespective f indicatr (Table 4). TABLE 3 Vine-spacing effect n grape and must cmpsitin. Spacing Sluble Titratable (m) slids acidity (OB) (gil) ph Anth- Anthcyanin Anthcyanin (mg/g dry cyanin (A 52 ) skin mass) (mg/skin) 3x3 21,72 d 7,38 bc 3,7 d 2,7 cd 4,14 cd,36 c 3 x 1,5 22,79 c 7,39 bc 3,15 c 1,97 d 3,94 d,33 c 2x2 23,66 ab 7,5 c 3,2 c 2,45 bc 4,91 bc,47 ab 2xl 23,33 bc 7,89 a 3,25 b 2,64 b 5,29 b,41 bc 1 x 1 23,48 abc 7,53 ab 3,28 ab 2,35 bcd 4,71 bcd,39 bc 1 x,5 24,16 a 7,71 ab 3,31 a 3,12 a 6,24 a,53 a Values in clumns fllwed by the same letter d nt differ significantly (p,5). TABLE 4 Vine-spacing effect n wine quality. Spacing % Acceptability Ttal Overall (m) arma quality Clur Acidity Hardness Bdy intensity (%) (%) 3x3 71,8 c 82,5 b 77,5 a 63,4 b 61, b 54,8 c 3 x1,5 72,8 c 83,4 ab 77,3 a 59,9 b 61,5 b 53, c 2x2 86,2 b 9,6 ab 8,3 a 73,9 a 65,3 ab 62,Ob 2xl 89,3 ab 9,7 ab 79,7 a 76,5 a 69,3 ab 69,6 a 1 x 1 94, ab 92,3 a 83,4 a 81,2 a 71,9 a 68,8 a 1 x,5 94,2 a 9,9 ab 8,3 a 8,7 a 73,2 a 7,3 a Values in clumns fllwed by the same letter d nt differ significantly (p,5).

6 4 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur Labur input: Calculating labur input fr canpy management, harvesting and pruning, it was evident that clsely spaced vines (1 x 1 m, 1 x,5 m) needed significantly higher input n a man hurs per hectare basis fr each practice, whereas the rest f the spacings were nt markedly different (Table 5). This is an imprtant cnsideratin in decisins n planting density. In additin, it may als playa big rle in the fixing f selling prices f wine and may push prices abve the prevailing market prices in rder t recver csts. TABLE 5 Vine-spacing effect n labur input fr canpy management, harvesting and pruning practices (man hurs per hectare). Spacing Suckering Sht Tpping and Harvesting psitining *sht psitining Pruning Ttal 3x3 394 b 258 c 77d 3 xl,5 4,4 b 27,1 c 9,3 d 2x2 48,6 b 25,3 c 1,2 d 2 xl 58, b 34,6 bc 15,4 c 1 x 1 16,4 a 56,4 b 22,8 b 1 xo,5 128,2 a 91,5 a 31,1 a 192c 122,7 bc 147,1 b 144,4 bc 26,1 a 239,5 a 495 d ,4 cd 253,9 65,2 c 296,4 67,5 c 319,9 14,2 b 495,9 122,6 a 612,9 Values in clumns fllwed by the same letter d nt differ significantly (p,5). *The secnd sht psitining was dne alng with tpping just after pea berry size X 3 m II 3 X 1.5 m 2 X 2 m X 1 m!21 1 X 1 m EJ 1 X,5 m Veraisn Ripeness LSD=2.53 LSD=1.17 (J) 5 a - 3 em 3-6 em 6-9 em a - 3 em 3-6 em 6-9 em Sil depth FIGURE 1 Vine-spacing effect n sil water cntent at veraisn and ripeness. S, Afr. J. Enl. Vitic., Vl. 19, N.2, 1998

7 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur em depth 45 em depth.a..... _ ::::::"'",. '>"" en Weeks after veraisn FIGURE 2 Vine-spacing effect n sil temperature at tw different depths frm veraisn t ripeness. 5 E 2 - r,m/ Rw directin E 2 - f1m Rw directin i,m-... i,-... -fa " /, c A "2 Il.! I I! E C> 1- /.. E C> 1-...;: t 1 /..\':...:! e... /. //i /./">,/,:.\.. OJ OJ;,. ::> ;",..,..... i,'.... ',.. \:..\ e /.l... /\.'.\.;... \:....c _ I i ;11,.'.,... 2' ;".1.1 i,... \ ' I. ;" I' '...,., Canpy height (12 em) 3 2 L._Ll/.", < L_ -1 _l...l '..i _::U--l>LOO--2J.> 3 Rw spacing (cm) Rw spacing (cm) 8: 9: 1: 12: 15: 16:3 8: 9: 1: 12: 15: 16:3 E 2 - Xt8i'fsg Rw directin i.-'lh:".. " ii,.,.'. 1 _.../l.\.\>\... j. /!,..... e -... j//..... j:,.l\:...'.,,: i ',\ : \ t- ii j'... l\\.... L L J. i.\,"'-_...:.. _-L_""":" Rw spacing (cm) 8: 9: 1: 12: 15: 16:3 8: 9: 1: 12: 15: 16:3 FIGURE 3 Vine-spacing effect n shading f between-rw sil and adjacent vines (East-West rw directin).

8 42 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur ai' a. -25 e -5 Ctl :.j:j c:: -75 C.....sa -1 1t1 (])...I -125 LSD= LSD= X 3 m II 3 X 1,5 m [J 2 X 2 m IS] 2 X 1 m EJ 1 X 1 m E3 1 X.5 m Veraisn FIGURE 4 Vine-spacing effect n leaf water ptential. Ripeness, cts :.j:; -5 C \1 3: -125.c () -15 CD -175 LSD= LSD = X 3 m!ii 3 X 1.5 m 2 X 2 m Q 2 X 1 m ELl 1 X 1 m EJ 1 X.5 m Veraisn FIGURES Vine-spacing effect n bunch water ptential. Ripeness

9 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur em 3-6 em 6-9 em t... y=,41x+56.3 (R2=.6492) - e... 1a C/) 8 6 " a,' -- --' II II,,-,,-,,,,-,','---'Y:"O.222X (R2=.827) II y= (R2=.2692) Leaf water ptential (kpa) FIGURE 6 Relatinship between sil water cntent f three sil layers and leaf water ptential at veraisn stage em 3-6 em 6-9 em """ II II y=.55x (R2= ".." y=.23x+9,4356 (R2=.2711) y=-o,5x= (R2=.912) II II II I -1 4 I J I I I Leaf water ptential (kpa) FIGURE 7 Relatinship between sil water cntent f three sil layers and leaf water ptential at ripeness stage. I

10 44 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur 12, em 3-6 em 6-9 em -e I- y=o.123x (R2=O.3594)......,"... ".,.", t- --j-- C/) 6 c :- y=o,34x (R2=O,1623) y=-o,ooo1x (R2=O,6) - 4 L- L-I IL I I Bunch water ptential (kpa) FIGURE 8 Relatinship between sil water cntent f three sil layers and bunch water ptential at veraisn stage r r- 8 I- 7 t-.....:. 6 t- 5 t-... y=o.58x (R2=O.5837).... _ a y=o.28x (R2=.4749)... y=o.3x (R2=O.262)... _ _- --_- _a I IL L-I I L_I Bunch water ptential (kpa) FIGURE 9 Relatinship between sil water cntent f three sil layers and bunch water ptential at ripeness stage.

11 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur , m a ca +=i -1 2 c +"" Q. '- 'ta tS Veraisn Ripeness,, / y=o.71x (R2=O.5788),, Bunch water ptential (kpa) FIGURE 1 Relatinship between leaf water ptential and bunch water ptential at veraisn and ripeness stages. -8 T""" --. g's -... "C " 6 Cd " 4 en 2 OL-_-.:::::: :-:-:-:-:-:-:-... :::::::::::::::::::::''''' 'A./'-A./'-/',/'-, A A.A./'-A. A./" AV :.:.: :-:.:-:-:.:.:.:-:.:-:-:.: -:.:-:-:-:.:.:.:.:.:.:" -:."/,, A. A. A.,"'A. /', /'- A./'-' /,-, :::::::::::::;::::::::::::::.,A..A /" A..A A..::::::::::::::::::::::::::::.,A./'-/,-, ::::::::::::::::::::::::::::.1'./"/,-,,,-/,-/,-/,, Spacing - O LSD= x3m II 3x1.5m D 2x2m KJ 2xim 1xim ixo.5m FIGURE 11 Vine-spacing effect n leaf sap abscisic acid cncentratin. s. Afr. J. Enl. Vitic., Vl. 19, N.2, 1998

12 46 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur..-.!: 12 C\i' E :g N 1 ) E '-"" >. +'" "> ().!: +'" C >. CI) +'".!: a X 3 m ill 3 X 1,5 m 2 X 2 m 2 X 1 m I'2l 1 X 1 m 1 X,5 m LSD=4.51 LSD=2.63 Veraisn Ripeness FIGURE 12 Vine-spacing effect n phtsynthetic activity. 4 3 x 3 m Ii! 3 x 1,5 m D 2 x 2 m 2 x 1 m [2] 1 x 1 m GJ 1 x,5 m 3,5... OC\( 3 :c OJ 2,5 C\( a 2 OJ... E W 1,5 ::J 3: 1,5 Veraisn Ripeness FIGURE l3 Vine-spacing effect n transpiratin:phtsynthesis rati, expressed as water use efficiency (WUE).

13 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur a - 3 em 3-6. H em em... -,A' , y=o.b2b9x+2.1 BOB (R2=O.59)...- >R. S2...- I.- CD 15 (f) , "......,,' ",,,'..... " ' ", " ' " " ', " ' "",,'-iii y=o.5133x (R2=O.7B73) 4 L- L L L Phtsynthetic activity (mg C/dm2/h) FIGURE 14 Relatinship between sil water cntent f three sil layers and phtsynthetic activity at veraisn a -3 em 3-6 em 6-9 em >R. L L- 1 I- a> 15 8 f : en 6f-,.... y=.2629x (R2=.623), y=o.141x+5,737 (R2=O.63) , ,, -,----, y=-.q125x (R2=.34) ,5 6 6,5 7 7,5 8 Phtsynthetic activity (mg Cq/dm2/h) FIGURE 15 Relatinship between sil water cntent f three sil layers and phtsynthetic activity at ripeness.

14 48 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur X 3.m 3. X 1.5m 2. X 2.m 2. X 1.m 1. X 1.m 1. X.5m " :j;- - -,, &-._ c f-' C> 8 C f-' 6..c en Weeks after budding FIGURE 16 Vine-spacing effect n sht length C\I' 3 E "'C 25..c:: en ets L- ets ca 15 1 ets m x 3.m I8J 3.m x 1.5m r:a 2.m x 2.m [S] 2.m x 1.m bj 1.m x 1.m 1.m x O.5m LSD=3.31 LSD=2.83 LSD=2.13 Berry set Pea size Veraisn Ripeness FIGURE 17 Vine-spacing effect n ttal leaf area per sht.

15 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur m X 3.m IQj 3.m X 1.5m [2J 2.m X 2.m &J 2.m X 1.m 1.m X 1.m!Ii 1.m X O.5m LSD=11.41 LSD=6.66 LSD= E -(\J & 1tS ::::. 4 cts LSD=8.85 LSD= Bunch zne Basal Middle Apical Average FIGURE 18 Vine-spacing effect n area per leaf. 14 r m X 3.m 3.m X 1.5m EJ 2.m X 2.m LSJ 2.m X 1.m EJ 1.m X 1.m 1.m X O.5m 12 -(\J E... 1 c: '>... 8 cts 6 LSD=.64 LSD=1.5 LSD=1.2 LSD= Berry set Pea size Veraisn Ripeness FIGURE 19 Vine-spacing effect n ttal leaf area per vine.

16 5 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur 3 )... en en r 2 E L- 1 Cl 3 X 3 m fill 3 X 1.5 m D 2 X 2 m 2 X 1 m [ZJ 1 X 1 m &J 1 X.5 m 2 LSD=1.2 LSD=1.87 LSD=3.e 468 Weeks frm pea size FIGURE 2 Vine-spacing effect n dry berry mass, LSD= LSD= en a> c L- a> en a> c L- a> )... en 1 E >- L- L- a> 5..c en u.. 3 X 3 m fill 3 X 1.5 m D 2 X 2 m 2 X 1 m EJ 1 X 1 m rs:j 1 X.5 m 2 LSD= Weeks frm pea size FIGURE 21 Vine-spacing effect n fresh berry mass. 1 LSD=13.e8 12

17 Plant Spacing Effects n Canpy Characteristics, Wine Quality and Labur 51 CONCLUSIONS It is clear that decisins n which plant spacing t use have far-reaching effects and shuld nt be taken lightly. The crrect plant spacing is critical in rder t utilise the available sil vlume t the best pssible ecnmic benefit. Physical between-rw distance had a majr direct effect n sil cnditins and n canpy micrclimate parameters such as light intensity, air flw and humidity thrughut the whle seasn, regulating phtsynthetic activity. The greatest effect n the physilgy f the vines was exerted frm veraisn nwards. Althugh vegetative grwth parameters indicated that clsely spaced vines were nt severely stressed, they nevertheless shwed physilgical symptms nrmally assciated with water stress, whereas widely spaced vines shwed definite signs f vercrpping. In additin, the micrclimate f clser-spaced vines was less favurable than that f widely spaced vines; their physilgical status nevertheless led t better grape cmpsitin and wine quality. Hwever, cnsidering all parameters, including land utilisatin, yield, wine quality and labur input, it is evident that medium-spaced vines (2 x 2 m, 2 x 1 m) cnsistently perfrmed ptimally. These spacings can therefre be used as guidelines fr recmmendatins under similar sil cnditins and viticultural practices. The data can als be extraplated t cnditins ther than thse described in this paper. It shuld be brne in mind that factrs such as sil ptential, cultivar vigur, rtstck, irrigatin, fertilisatin, trellising system, and mechanical pruning and harvesting may affect the chice f a particular plant spacing fr a given situatin. In general, narrwer spacing can be cnsidered under cnditins where lw vigur is expected and/r lcalities are marked by pr sils. In cntrast, high vigur and/r rich, heavy sils will require wider spacing. The clur and texture f the sil play an imprtant rle in the absrptin and reflectin f slar energy, with implicatins fr rt grwth, vegetative develpment, and clur and flavur f grapes. It shuld be stressed, hwever, that efficient accmmdatin f abvegrund grwth is f the utmst imprtance under all circumstances in rder t btain maximum and cntinued prductin, grape and wine quality, as well as lngevity f the grapvine. LITERATURE CITED ARCHER, E. & STRAUSS, H.C., The effect f plant density n rt distributin f three-year-ld grafted 99 Richter grapevines. S. Afr. 1. Enl. Vitic. 6, ARCHER, E. & STRAUSS, H.e., The effect f plant spacing n the water status f sil and grapevines. S. Afr. 1. Enl. Vitic. 1, ARCHER, E. & STRAUSS, H.e., 199. The effect f vine spacing n sme physilgical aspects f Vitis vinifera L. (ev. Pint nir). S. Afr. 1. Enl. Vitic. 11, CRAM, WI. & PITMAN, M.G., The actin f abscisic acid n in uptake and water flw in plant rts. Aust. 1. Bii. Sci. 25, DAVIES, WI., METCALFE, I., LODGE, T.A. & DA COSTA,AR., Plant grwth substances and the regulatin f grwth under drught. Aust. 1. Plant Physil. 13, DUNCAN, R.A., STAPLETON, I.I. & LEAVITT, G.M., Ppulatin dynamics f epiphytic mycflra and ccurrence f bunch rts f wine grapes as influenced by leaf remval. Plant Pathlgy 44, GREENSPAN, M.D., SHACKEL, K.A. & MATTHEWS, M.A., Develpmental changes in the diurnal water budget f the grape berry expsed t water deficits. Plant Cell Envirn. 17, HOFACKER, W., Untersuchungen zur Stffprduktin der Rebe unter dem Einfluss wechselnder Bdenwasserversrgung. Vitis 16, HUNTER, I.I., Plant spacing implicatins fr Vitis vinifera L. cv. Pint nir/99 Richter I. Sil characteristics, rt grwth, dry matter partitining, dry matter cmpsitin, and sil utilisatin. S. Afr. 1. Enl. Vitic. 19, HUNTER, J.J., DE VILLIERS, O.T. & WATTS, J.E., The effect f partial defliatin n quality characteristics f Vitis vinifera L. cv. Cabernet Sauvignn grapes. II. Skin clr, skin sugar, and wine quality. Am. 1. Enl. Vitic. 42, HUNTER, J.J., RUFFNER, H.P., VOLSCHENK, e.g. & LE ROUX, D.J., Partial defliatin f Vitis vinifera L. cv. Cabernet Sauvignn/99 Richter: Effect n rt grwth, canpy efficiency, grape cmpsitin and wine quality. Am. 1. Enl. Vitic. 46, HUNTER, J.J. & VISSER, J.H., The effect f partial defliatin, leaf psitin and develpmental stage f the vine n the phtsynthetic activity f Vitis vinifera L. cv. Cabernet Sauvignn. S. Afr. 1. Enl. Vitic. 9 (2) : HUNTER, J.J. & VISSER, J.H., 199. The effect f partial defliatin n grwth characteristics f Vitis vinifera L. cv. Cabernet Sauvignn II. Reprductive grwth. S. Afr. 1. Enl. Vitie. 11, LANG, A & DORING, H., Partitining cntrl by water ptential gradient: Evidence fr cmpartmentatin breakdwn in grape berries. 1. Exp. 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