Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Cabernet Sauvignon is the most planted red cultivar in South Africa and the second
most planted red cultivar in the Olifants River region. The cultivar is prone to vigorous
growth with low yields. Excessive irrigation could accentuate these cultivar
characteristics. Considering the foregoing, the aim of the study was to describe how
Cabernet Sauvignon will react to climate, soil type (texture) and irrigation within the
Lower Olifants River wine region to enable growers to make the right decisions
regarding long term as well as short term cultivation practices. This study is part of a
project carried out by the ARC Infruitec-Nietvoorbij at Stellenbosch to determine the
effects of soil type and atmospheric conditions on yield and wine quality of Cabernet
Sauvignon in different grape growing regions of South Africa. Similar studies are being
carried out in the Orange River, Stellenbosch and Swartland regions of South Africa.
The Lower Olifants River region could be divided into three climatic regions.
Furthermore, two climatic regions is evident regarding the formation of grape wine
colour and aromas. Proximity to the Atlantic Ocean would play an important role in a
cultivar establishment policy.
The variation in stem water potential (ΨS) could be related to soil water status
expressed in terms of matric potential (ΨM). In the case of sandy soils, ΨS decreased
substantially more as the ΨM decreased compared to the sandy loam soils. The reason
could be that the unsaturated hydraulic conductivity in sandy soils decreased more
rapidly as the ΨM decreased compared to the heavier soils. Thus could explain why the
grapevines in the sandy soils experienced more water stress than the ones in the sandy
loam soils at a given ΨM.
Climate had a strong influence on grapevine water status with grapevines nearer to
the ocean experiencing less water stress compared to the ones further inland. This was
especially true for grapevines in the sandy soils.
Vegetative growth and yield of grapevines in the sandy soils were more sensitive to
water deficits compared to the ones in the sandy loam soils. For deficit irrigated
grapevines in the sandy soils, vegetative growth and yield decreased by ca. 30% when
ca. 55% less water was applied from flowering to harvest. Yield reduction were ca. 15%
with no or very little influence on vegetative growth with ca. 80% reduction in water
applied from flowering to harvest for grapevines in the sandy loam soils.
The influence of soil texture on wine quality and style were evident under intensive
irrigation as well as over different climatic regions. Overall sensorial potential wine
quality of grapevines in sandy soils tended to be higher compared to the ones in the
sandy loam soils. Deficit irrigation tended to increase wine colour intensity, irrespective
of soil texture. Furthermore, deficit irrigation in sandy loam soils tended to increase wine
fullness and the berry characteristics of the wine. Berry characteristics of wines from the
sandy soils tended to be higher compared to the ones from the sandy loam soils. Too
severe water deficits in sandy soils could be detrimental to wine quality. Climate tended to have an influence on wine style of grapevines in the sandy soils with wines produced
further away from the ocean tended to have higher berry characteristics.
Irrigation management could be a powerful tool to manipulate the grapevine in
sandy soils. For grapevines the sandy loam soils in addition to regulated deficit
irrigation, additional canopy management practices could be needed to improve wine
quality. / AFRIKAANSE OPSOMMING: Cabernet Sauvignon is die mees aangeplante rooidruif kultivar in die Suid-Afrikaanse
wynbedryf. In die Olifantsriver streek is dit naas Shiraz, die tweede mees aangeplante
rooidruif kultivar. Cabernet Sauvignon is bekend as ‘n groeikragtige skaamdraer. Indien
oorbesproei word, kan hierdie potensiële nadelige eienskappe nog meer na vore tree.
Die doel van die studie is om die invloed van die klimaat, grond en besproeiing op
Cabernet Sauvignon se vegetatiewe groei, produksie en wyngehalte in die Benede
Olifantsrivier streek te bepaal. Hierdie inligting kan produsente help om ingeligte kortsowel
as langtermyn besluite te maak rakende die verbouing van Cabernet Sauvignon.
Hierdie studie vorm deel van ‘n breër studie in die Suid-Afrikaanse wynbedryf, gedryf
deur die Landbou Navorsingsraad (LNR) Infruitec-Nietvoorbij, Stellenbosch om die
invloed van atmosferiese toestande en grond op die produksie en wyngehalte van
Cabernet Sauvignon te bepaal. Soortgelyke projekte word uitgevoer in die Oranjerivier,
Stellenbosch en Swartland wynstreke.
Die Benede Olifantsrivier streek kan verdeel word in drie klimaatstreke op grond
van temperatuurdata. In terme van die ontwikkeling van druifkleur en aromas, kan die
streek verdeel word in twee klimaatstreke. Die afstand vanaf die Atlantiese Oseaan kan
‘n belangrike rol speel in die ontwikkeling van ‘n kultivarriglynplan vir die streek.
Grondwaterstatus, uitgedruk as die matrikspotensiaal (ΨM), kan aanleiding gee tot
variasie in middag blaarwaterpotensiaal (ΨS) lesings. Die ΨS van die sand gronde
verlaag vinniger soos die ΨM verlaag invergelyke met die sandleem gronde. Dit kan
moontlik wees as gevolg van die verskil in die grond onversadigde hidroliese
konduktiwiteit. Sand gronde se hidroliese konduktiwiteit verlaag vinniger soos die ΨM
verlaag, invergelyke met sandleem gronde. Dit verklaar waarom wingerde in sand
gronde by dieselfde ΨM, meer waterspanning ondervind as wingerde in sandleem
gronde.
Klimaat het ‘n invloed op die waterstatus van die wingerdstok. Wingerde nader aan
die see het minder waterspanning ondervind invergelyke met wingerde wat verder in die
binneland geleë is. Dit was veral die geval met wingerde in die sand gronde.
Vegetatiewe groei en produksie van wingerde in die sand gronde is meer sensitief
vir waterspanning as wingerde in die sandleem gronde. Tekortbesproeiing in die sand
gronde het die groei asook produksie met ongeveer 30% verlaag deur ongeveer 55%
minder water toe te dien vanaf blom tot oes. In teenstelling daarmee is die produksie
van wingerde in die sandleem gronde met ongeveer 15% verlaag met geen tot baie min
verlaging in die groeikrag. Ongeveer 80% minder water is toegedien vanaf blom tot oes.
Grondtekstuur kan wyngehalte en -styl beïnvloed ten spyte van intensiewe
besproeiing en klimaatsverskille. Sensoriese potensiële wyngehalte van wingerde in die
sand gronde was beter invergelyke met dié van die sandleem gronde. Die wyne vanaf
die sand gronde het ook geneig om oor meer bessie intensiteit te beskik as wyne vanaf
die sandleem gronde. Tekortbesproeiing neig om die wynkleur intensiteit te verhoog,
ongeag van grondtekstuur. Tekortbesproeiing in die sandleem gronde kan ook die
volheid van die wyne verbeter, asook die bessie intensiteit van die wyn verhoog. Te hoë waterspanning in die sand gronde kan wyngehalte nadelig beïnvloed. Klimaat kan ook
die wynstyl vanaf sand gronde beïnvloed met wyne verder vanaf die see wat oor meer
bessie intensiteit beskik as wyne nader aan die see.
Beheerde tekortbesproeiing kan as ‘n kragtige hulpmiddel gebruik word om
wingerde in die sand gronde te manipuleer. Vir wingerde in die sandleem gronde,
addisioneel tot beheerde tekortbesproeiing en normale loofbestuurspraktyke, kan ekstra
loofbestuurspraktyke bv. die verwydering van sylootlote, dalk nodig wees om
wyngehalte te verbeter.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4342 |
| Date | 03 1900 |
| Creators | Bruwer, Rachel Jacoba |
| Contributors | Myburgh, P. A., Deloire, A., University of Stellenbosch. Faculty of Agrisciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 208 p. : ill. |
| Rights | University of Stellenbosch |
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