Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Wind, as a component of the environment, contributes to the viticultural concept of
terroir in the South Western Cape region of South Africa. Many other components
also contribute to terroir (e.g. soil, altitude, direction of slope, etc.) and it is difficult to
quantify the contribution of each. A good terroir promotes slow and complete ripening
of the berries. A vineyard on such a terroir produces good quality crops over time and
the effects of climatic extremes on the performance of the vine are limited by this
terroir.
Although grapevines in the South Western Cape are exposed to strong synoptic
southerly and southeasterly winds during the growing season and sea breezes add to
the effect of wind in coastal areas, little is known about the effect of wind on
grapevine performance. This preliminary study was undertaken to obtain more
information on the effect of wind on some morphological and reproductive
characteristics of Merlot nair. The aim was to obtain preliminary data which can serve
as a basis for future studies on the effect of wind on grapevine performance.
Important differences .in wind speed were measured spatially in a selected vineyard
and exposure to wind was observed to result in essential viticultural differences. The
effect of wind on vegetative parameters, canopy density, yield, berry composition and
wine quality was investigated. Wind caused leaves on primary shoots of exposed
vines to be smaller, but increased lateral growth in their fruiting zones. Sheltered
vines had longer shoots but no significant differences were measured concerning
cane diameter and pruning mass. Although it was expected that sheltered vines
would have denser canopies, similar canopy densities were measured for both
treatments. Vines exposed to wind responded with decreased stomatal conductance.
As a result, leaf temperature was affected, showing differences between sheltered
and exposed vines. Sheltered vines had more bunches per vine but fewer berries per
bunch. As a result, bunches of sheltered vines were smaller than those of exposed
vines. No significant difference was observed concerning the yield under the two
treatments. The effect of wind on stomatal conductance had an essential impact on
berry composition, thus directly influencing the quality of wine. Grapes from exposed
vines showed a higher colour index. Berries from sheltered vines had significantly
lower pH values and potassium concentrations and the malic acid content was lower
than in berries from exposed vines.
Wine from sheltered vines had more vegetative undertones in comparison with the
stronger fruity character of exposed vines. A better acid balance, together with
superior complexity (fullness/mouth feel), contributed to the better overall quality
identified during the evaluation of wine produced from sheltered vines. / AFRIKAANSE OPSOMMING: Wind as 'n omgewingsfaktor dra by tot die wingerdkundige konsep van terrair in die
Suidwes-Kaap streek van Suid-Afrika. Baie ander komponente dra ook by tot terrair
(bv. grond, hoogte bo seespieël, rigting van helling, ens.) en dit is moeilik om die
bydrae van elk te kwantifiseer. 'n Goeie terrair bevorder stadige en volledige
rypwording van die korrels. 'n Wingerd gevestig op so 'n terrair produseer jaarliks hoë
kwaliteit oeste met goeie sapsamestellings en die terrair beperk die negatiewe
invloed van uiterste klimaatsomstandighede op wingerdprestasie.
Alhoewel wingerde in die Suidwes-Kaap gedurende die groeiseisoen aan sterk
sinopties suidelike en suid-oostelike winde blootgestel is en seebriese 'n bykomstige
effek in kusgebiede het, is daar beperkte kennis oor die effek wat wind op
wingerdprestasie het. Hierdie voorlopige studie is onderneem om meer inligting oor
die effek van wind op sommige morfologiese en reproduktiewe eienskappe van
Merlot noir in te win. Die mikpunt was om verwysingsdata in te samel wat as 'n basis
vir toekomstige studies oor die effek van wind op wingerdprestasie kan dien.
Belangrike verskille in windspoed is gemeet in die geselekteerde wingerd en
waarnemings het getoon dat blootstelling aan wind tot kenmerkende wingerdkundige
verskille gelei het. Die effek van wind op vegetatiewe parameters, lowerdigtheid,
oesgrootte, druifsamestelling en wynkwaliteit is ondersoek. Wind het kleiner blare op
primêre lote van wind-blootgestelde stokke veroorsaak, maar het laterale groei in hul
trossones verhoog. Wind-beskermde stokke het langer lote gehad maar geen
noemenswaardige verskille is ten opsigte van lootdeursnee en snoeimassa gemeet
nie. Die verwagting was dat beskermde stokke digter lower sal hê, maar soortgelyke
lowerdigthede is vir beide beskermde en wind-blootgestelde stokke gemeet. Stokke
blootgestel aan wind het met 'n verlaagde huidmondjiegeleiding gereageer. Gevolglik
is blaartemperatuur beïnvloed, met verskille tussen beskermde en blootgestelde
wingerde. Beskermde stokke het meer trosse per stok maar minder korrels per tros
gehad. As gevolg hiervan was die trosse van beskermde stokke kleiner as die van
blootgestelde wingerde. Geen noemenswaardige verskille in die oesgroottes is
tussen die twee behandelings gemeet nie. Die effek van wind op
huidmondjiegeleiding het 'n belangrike impak op druifsamestelling gehad en het
daarom 'n direkte invloed op wynkwaliteit gehad. Druiwe van blootgestelde stokke
het 'n hoër kleurindeks getoon. Die pH en kaliumkonsentrasie van druiwe van
beskermde stokke was merkbaar laer en het minder appelsuur gehad as die van die
blootgestelde stokke.
Die wyn van beskermde stokke het meer vegetatiewe geure gehad in vergelyking
met die sterker vrugtige karakter van blootgestelde stokke. 'n Beter suurbalans, tesame met goeie kompleksiteit (volheid/mondgevoel), het egter meegebring dat
beskermde stokke 'n beter wyngehalte lewer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50486 |
| Date | 12 1900 |
| Creators | Pienaar, Jacobus Wilhelm |
| Contributors | Carey, Victoria, Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology . |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 92 p. : ill. |
| Rights | Stellenbosch University |
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