Optimising productivity in vineyards and potential effects on grape and wine composition for a specific production goal

Davel, Annette (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: In this study three trellis/training systems (double split cordon gable, vertical shoot positioning and sprawling systems) located in a Vitis vinifera cv. Shiraz vineyard in Stellenbosch were investigated to determine how grapevine productivity and grape- and wine composition can be altered as a result of differing canopy microclimate, grapevine balance regimes and yield component compensation reactions. Two sprawling training systems (double and standard bud load in relation to the vertically shoot positioned system) were combined in the second season and subjected to a lighter pruning, simulating mechanical pruning. Pruning and harvest data were collected over two growth seasons from each grapevine in the plot, which also displayed within-treatment and vineyard vigour-, yield- and grapevine balance variability. The large number of single-vine replicates made it possible to determine main yield components, such as bud load, budburst percentage, fruitfulness, bunch- and berry size as well as berries per bunch, and to investigate some primary components responsible for grapevine productivity. Shoot growth, shoot characteristics (leaf area, lateral number, internode length, and leaf age), canopy microclimate, physiological measurements, water status and ripening evolution were recorded to establish trends between grapevine balance and associated compensation reactions. Qualitative descriptive analysis was performed on the wines produced from each treatment in the second season. Increased bud load led to increased shoot numbers and yield, but with decreased bunch mass and grapevine vigour, in terms of total cane- and mean mass per cane and shoot length. The gable trellis system produced the highest yield between treatments in both seasons, but due to trellis conversion completion in the first season, low vigour was present. For this reason, imbalanced grapevine conditions occurred in terms of high yield to cane mass ratios (Y/CM) and low leaf area to yield ratios (LA/Y) and consequently delayed ripening. Nevertheless, the gable trellis system seemed to reach maximum productivity, as the yield between seasons remained relatively similar. The main yield component responsible for yield difference in the first season was the number of bunches produced per shoot (fertility), while increased budburst percentage and bunch mass in the second season affected yield most. More shoots led to decreased fertility and increased bunch mass in this treatment, and improved growth and high yields during the second season resulted in more desirable grapevine balance, thereby not affecting ripening negatively. The two sprawling systems only differed according to shoot number, with the double sprawling system (double the amount of buds) producing twice as many shoots and consequently higher yields. Simulated mechanical pruning, in the second season, decreased grapevine vigour as expected but increased yield considerably as a result of increased fertility. However, imbalanced Y/CM ratios occurred, delayed ripening, and a highly exposed canopy bunch zone which increased the process of leaf degradation and the occurrence of water deficits. The VSP treatment produced highly vigorous grapevines together with low yields in both seasons and as a result increased canopy density and decreased Y/CM ratios. Grapevine balance, bud load and canopy density were most associated with sensory wine attributes. The intensity of fruity wine attributes increased and vegetative wine attributes decreased as bud load and Y/CM ratios increased and canopy density decreased. The sprawling treatment displayed the highest Y/CM ratio and bud load as well as the least dense canopy. Therefore the sprawling training system produced wines containing the highest fruity attributes which is generally desirable in new world Shiraz. The dense canopy as a result of vigorous growth, low Y/CM and bud load of the VSP treatment produced wines dominated by vegetal attributes. The gable treatment, which displayed Y/CM ratios, bud load and canopy densities with general values between the VSP and sprawling treatments, produced wines with vegetal and fruity attributes, with the latter probably being more dominant. Changing trellising-, training- and pruning systems clearly led to the production of different wine styles. Grapevine balance, canopy density and pruning severity should be taken into consideration when attempting to produce wines intended for specific production goals. Therefore, increased yield as a result of alternative pruning-, training- and trellising systems does not necessarily affect wine composition negatively, if not more beneficially, and should be considered as a solution regarding production profitability.

AFRIKAANSE OPSOMMING: In hierdie studie word drie prieelstelsels (dubbel verdeelde kordon gewel, vertikale lootposisionering- en vryloot stelsels), geleë in ʼn Vitis vinifera cv. Shiraz wingerd in Stellenbosch ondersoek om te bepaal hoe wingerdstokproduktiwiteit, druif- en wynsamestelling gewysig kan word vanweë verskillende lowermikroklimaat, wingerdstokbalanse asook opbrengskomponent kompensasiereaksies. Twee vryloot prieelstelsels (dubbel- en normale oogladings) is in die tweede seisoen gekombineer en aan ʼn ligter snoei aksie onderwerp, om meganiese snoei na te boots. Snoei- en oesdata van elke stok is ingesamel in die perseel oor ʼn tydperk van twee groeiseisoene, wat variasie in terme van groeikrag, opbrengs en balans ten toon gestel het binne elke behandeling asook tussen behandelings in die eksperimentele wingerd. Die groot aantal enkelstok-herhalings het dit moontlik gemaak om hoof opbrengskomponente, soos ooglading, botpersentasie, vrugbaarheid, tros- en korrelgrootte, sowel as korrels per tros te bepaal en om sekere primêre komponente, verantwoordelik vir wingerdproduksie te ondersoek. Lootgroei, lootkenmerke (blaararea, sylootgetalle, internode lengtes en blaarouderdom), lowermikroklimaat, fisiologiese metings, waterstatus en rypwordingsevolusie is gemeet om tendense tussen wingerdbalans en geassosieerde kompensasie te bepaal. Kwalitatiewe beskrywingsanalises is in die tweede seisoen op die wyne van elke behandeling toegepas. Toename in ooglading het gelei tot toename in lootgetalle en opbrengs, maar ʼn afname in trosmassa en groeikrag. Die afname in groeikragtigheid was uitgedruk in terme van snoeimassa, massa per loot en lootlengte. Die gewelprieelstelsel het in beide seisoene die hoogste opbrengs gelewer, maar is deur laer groeikrag gekenmerk, meegebring deur die vergroting van die stokraamwerk op die groter prieel. Vir hierdie rede, het ongebalanseerde wingerdtoestande voorgekom in terme van hoë oes tot lootmassaverhoudings (O/LM) en lae blaararea tot opbrengsverhoudings (BA/O) en gevolglik was rypwording vertraag. Nieteenstaande het dit voorgekom asof die gewelprieel maksimum produktiwiteit bereik het, aangesien die opbrengs tussen seisoene relatief konstant gebly het. Die hoof opbrengskomponent verantwoordelik vir die opbrengsverskil in die eerste seisoen, was die hoeveelheid trosse geproduseer per loot (vrugbaarheid), terwyl verhoogde botpersentasie en trosmassa die opbrengs in die tweede seisoen die meeste beïnvloed het. Meer lote het gelei tot verlaagde vrugbaarheid en verhoogde trosmassa in hierdie stelsel, en verbeterde groei en hoër opbrengs gedurende die tweede seisoen het gelei tot ‘n meer gewensde wingerstokbalans, wat rypwording nie negatief beïnvloed het nie. Die twee vryloot prieelstelsels het slegs verskil ten opsigte van lootgetalle, terwyl die dubbel vryloot prieelstelsel (met dubbele aantal oë) twee keer die hoeveelheid lote geproduseer het en gevolglik hoër opbrengste gelewer het. Nagebootste meganiese snoei in die tweede seisoen het wingerdgroeikrag soos verwag laat afneem, maar het opbrengs aansienlik verhoog as gevolg van meer trosse. Nogtans het ongebalanseerde O/LM verhoudings, vertraagde rypwording en ʼn meer blootgestelde lower veral in die trossone voorgekom wat die proses van blaaragteruitgang en die voorkoms van watertekorte/stres verhoog het. Die VLP stelsel het hoë groeikrag wingerdstokke opgelewer tesame met lae opbrengste in beide seisoene wat gelei het tot verhoogde lowerdigthede en verlaagde O/LM verhoudings. Wingerdstokbalans, ooglading en lowerdigtheid was die meeste geassosieer met sensoriese wynkenmerke. Die intensiteit van vrugtige wynkenmerke het verhoog en vegetatiewe wynkenmerke het verlaag soos ooglading en O/LM verhoudings verhoog het en lowerdigtheid afgeneem het. Die vryloot stelsel het die hoogste O/LM verhoudings en ooglading gehad, sowel as die minste digte lower. Dit is die rede waarom die vryloot stelsel wyne opgelewer het wat die mees prominente bessie/vrugtige kenmerke gehad het, wat algemeen as gewens beskou kan word in ʼn nuwe wêreld Shiraz. Die digte lower, as gevolg van hoë groeikrag, lae O/LM en ooglading van die VLP stelsel, het wyne opgelewer wat meer prominent groen was. Die gewelstelsel, wat O/LM verhoudings, ooglading en lowerdigtheid opgelewer het met algemene waardes tussen die VLP en vryloot prieelstelsels het wyne tot gevolg gehad met beide groen en bessie kenmerke, met laasgenoemde waarskynlik die mees dominante kenmerk. Die verandering van prieel-, oplei- en snoeistelsels het duidelik gelei tot die produksie van verskillende wynstyle. Wingerdbalans, lowerdigtheid en die graad van snoei behoort in ag geneem te word wanneer wyne geproduseer word vir spesifieke produksiedoelwitte. Daarom sal verhoogde opbrengs, as gevolg van alternatiewe snoei-, oplei- en prieelstelsels nie noodwendig wynsamestelling negatief beïnvloed nie, indien nie eerder meer voordelig nie, en dit behoort oorweeg te word as ‘n oplossing vir winsgewende produksie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98140
This item appears in the following collections: