Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This study is an integral part of a multidisciplinary research project concerning the effects of
soil and climate on wine quality. The motive, which led to the setting up of this project, was
that producers could not determine beforehand whether a specific location would yield wines
of high or low quality. If a specific cultivar were to be planted at the wrong location, then it
was likely that wine of table quality would result, rather than the export quality wine that was
intended. The long term objectives of this multidisciplinary project were the compilation of
guidelines by means of which different sites may be classified according to their potential for
the production of high quality wines, and the identification of the most important climatic and
soil factors responsible for differences in wine quality and character. In this multidisciplinary
project, measurements (soil water, leaf water potential, cane mass and yield) were made
under dry land conditions in Sauvignon blanc vineyards at six different localities: five in the
Stellenbosch district (Simonsberg, Kuils River, Helshoogte, Papegaaiberg and Devon Valley)
and one in Durbanville. Each vineyard was owned by a private commercial producer. The
vines were approximately 10 years old in all cases, and were trained on a hedge system.
Measurements were made in plots, each of which contained 20 vines. Two different soil
types were identified at each locality. Vine growth and wine quality differed markedly on
these contrasting soils, even though they were located in close physical proximity. The
measurements that were made at high and low production plots at each locality during this
study were obtained from points which were not more than 60 m metres apart. An automatic
weather station was erected halfway between the two, contrasting, experimental plots.
Within the overall scope of the multidisciplinary project, the study which forms the subject of
this thesis, concentrated on the effects of soil parent material as a soil forming parameter and
as a possible predetermining character with regard to vine growth and wine character. From
literature it was clear at the outset of this work that the geology of the coastal wine region is
very complex and varies over short distances. The geological history indicates different types
of rock formation and rock forming process (sedimentary, igneous as well as metamorphic),
plate tectonic activity, mountain building, erosion and weathering, over a period of
approximately 1 000 million years. The present landscape includes a coastal plane, hills, and
eroding mountains.
Statistical analyses indicated that the soils from the different localities could mainly be
characterised in terms of differences in their sand size fractions. Soils from Durbanville are
dominated by fine sand and correlates with the underlying phyllitic shales. Soils from Kuils
River contain significantly more coarse sand when compared with the other sites. This
appears to be a reflection of the underlying coarse granitic material, and implies that in situ
weathering played an important role in soil development. .The data did not, however, prove
that the Kuils River soils formed solely from underlying rocks. The gravel and stone fraction for the Kuils River soils were nevertheless correlated with those of the underlying parent
material. Soils from Helshoogte and Simonsberg (both of which are underlain by granites),
Papegaaiberg and Devon Valley (both underlain by hornfels) were not significantly dominated
by any particular sand fraction. Soils from these localities therefore did not only reflect the
underlying material as a source of soil parent material. This implied mixing of parent material
and/or the incursion of eolian sand at Helshoogte, Simonsberg and Devon Valley. A marine
incursion may have affected the soil parent material at Papegaaiberg.
In order to obtain more information concerning the origins and possible mixing of parent
materials prior to and during soil formation, samples from the different soil horizons in each
profile were subjected to a chemical analysis. Particular emphasis was placed on potassium,
which is an extremely important nutrient mineral element, from the viewpoints of vine growth
and wine quality. Because the soils used in this study were all located in production
vineyards, the probability that fertiliser residues would have contaminated the soils was high.
The lower soil horizons were considered to be least affected by this contamination and
therefore most likely to be indicative of the natural soil chemical composition. However, the
lower horizon K content of the soils in this study could not be reliably correlated with any
known or predicted characteristic that might link the soil parent material with local rock types.
At Durbanville, both soils contained small quantities of K in the lower horizons, reflecting the
underlying phyllitic shales, but at Devon Valley and Papegaaiberg, the lower horizons
contained more K than expected. The soils at these localities are situated on hornfels,
containing low quantities of K. The large quantities of K in the soils may have indicated that
these soils are situated close to a granite/Malmesbury contact zone. Soils from Kuils River,
Simonsberg and Helshoogte are situated on K-rich porhyritic granites and it was expected
that these soils would contain relatively large quantities of K in the lower horizons. This,
however, was not the case. It was therefore concluded that dilution with K-poor material had
taken place. Such material could have been derived from higher-lying sandstones, or from
eolian processes during the Cenozoic. Alternatively, the K content of the soil might have
been depleted by long continued leaching.
A semi-quantitative analysis of the minerals in the soil clay fractions was also carried out.
The objective was to identify the clay minerals that were present in the different soil horizons
and to relate the minerals to weathering conditions. Evidence linking the minerals in the clay
fractions of the soil samples with the mineralogical composition of the soil parent materials
was sought. The clay fraction mineralogy data indicated that all soils in the study area are in
an advanced stage of weathering and are dominated by kaolinite, and in certain soils quartz.
It was difficult to relate these minerals directly with soil parent material because the primary
minerals originating from the soil parent materials have been extensively broken down. The
simultaneous presence of quartz and gibbsite in the clay fraction of both soils at Simonsberg,
Helshoogte and Durbanville as well as one soil form from bath Kuils River and Simonsberg, indicated non-uniform distribution of clay fraction minerals, indicating that different stages of
weathering were present during soil formation. This could have been a result of mixing of
parent materials, but may also reflect different periods of weathering of the same material.
Both soils at Papegaaiberg, both soils at Devon Valley and other soils at Simonsberg and
Kuils River indicated uniform clay fraction mineralogy distribution, mainly because the
absence of gibbsite is related to the presence of quartz in the clay fraction.
The soil characteristics, as determined in this study, were also compared with vine growth,
wine quality and wine character, as obtained in the broader multidisciplinary research project.
For most soils in this study, an increase in clay fraction kaolinite was associated with a
reduction in vegetative growth, overall wine quality, and fresh vegetative character. An
increase in clay fraction quartz was associated with higher overall wine quality. Increased
shoot growth also affected fresh vegetative character positively. Better growth occurred on
higher altitudes and this resulted, for Sauvignon blanc, in higher wine quality. Wines
produced from vines situated on both phyllitic shales and porhyritic granites showed high
quality (Durbanville and Helshoogte), but both were related to low clay fraction kaolinite
content and high altitude. It was not possible to relate parent material directly with vine
growth, wine quality and/or wine character. The lowest quality wines, however, were
produced from vines situated on hornfels (Papegaaiberg and Devon Valley), both containing
high quantities of clay fraction kaolinite and situated on low altitudes. High levels of K in soils
containing high levels of clay fraction kaolinite may have been partly responsible for low wine
quality obtained on such soils. / AFRIKAANSE OPSOMMING: Hierdie studie vorm 'n integrale deel van 'n multi-dissiplinêre navorsingsprojek oor die effek
van grond en klimaat op wynkwaliteit. Die motivering wat gelei het tot die beplanning van
hierdie projek, was dat produsente nie vooraf kon bepaal of 'n spesifieke lokaliteit wyne kan
produseer van hoë of lae kwaliteit nie. Indien 'n spesifieke kultivar op die verkeerde lokaliteit
geplant word, sou dit waarskynlik tot In gewone tafelwyn lei, instede van 'n wyn van
uitvoergehalte. Die langtermyn doelwitte van die multi-dissiplinêre projek was om riglyne te
ontwikkel om verskillende lokaliteite te klassifiseer na aanleiding van·hul potensiaal om hoë
kwaliteit wyne te produseer, asook om die belangrikste klimaats- en grondfaktore
verantwoordelik vir die produksie van hoê kwalitiet wyne te identifiseer. In hierdie multidissiplinêre
projek was metings (plant beskikbare water, blaarwater potensiaal, lootmassa en
oes) onder droêland toestande bepaal in Sauvignon blanc wingerde by ses verskillende
lokaliteite: vyf in die Stellenbosch distrik (Simonsberg, Kuilsrivier, Helshoogte, Papegaaiberg
and Devon Valley) en een in Durbanville. Elke wingerd is besit deur 'n kommersiêle
privaatprodusent. Die stokke was ongeveer 10 jaar oud in alle gevalle en opgelei op 'n
heining sisteem. Metings was in eksperimentele blokke van 20 stokke elk uitgevoer. Twee
verskillende grondtipes is by elke lokaliteit identifiseer. Lootgroei en wynkwaliteit het
merkbaar verskilop die kontrasterende gronde, selfs waar gronde nabyaanmekaar was. Die
metings is Liitgevoer op hoë- en lae produksie eksperimentele blokke waar gronde by
spesifieke lokaliteite nie verder as 60 meter was nie. 'n Outomatiese weerstasie was halfpad
tussen die twee kontrasterende grondtipes by elk van die ses lokaliteite opgerig.
Binne die algemene omvang van die multi-clissiplinêre projek, het die studie wat die
onderwerp van hierdie tesis is, gekonsentreer op die effek van moedermateriaal as
grondvormende parameter asook as moontlike voorspeller van wingerdgroei en wynkarakter.
Dit was duidelik uit die literatuur dat die geologie van die Wynkusstreek baie kompleks is en
oor kort afstande varieer. Die geologiese geskiedenis dui daarop dat verskillende tipes
gesteentes en verskillende prosesse van gesteente-vorming (sedimentêr, stollings- en
metamorfe), plaattektoniese aktiwiteit, orogenese, erosie en verwering, oor 'n periode van
ongeveer 1 000 miljoen jaar plaasgevind het. Die huidige landskap sluit kusvlaktes, heuwels
en geêrodeerde berge in.
Statistiese analises het aangetoon dat die gronde van die verskillende lokaliteite hoofsaaklik
in terme van verskille in sandgrootte fraksies onderskei kon word. Gronde van Durbanville is
gedomineer deur fyn sand en korreleer met onderliggende fillietiese skalies. Gronde van
Kuilsrivier bevat betekenisvol meer growwe sand wanneer dit vergelyk word met die ander
lokaliteite. Dit is waarskynlik afkomstig vanaf die onderliggende growwe granitiese materiaal
en impliseer dat in situ verwering 'n belangrike rol gespeel het in grondontwikkeling. Die data
het egter nie bewys dat die gronde van Kuilsrivier slegs uit die onderliggende graniete gevorm het nie. Die gruisfraksies in die gronde by Kuilsrivier was tog vergelykbaar met die
onderliggende materiaal. Gronde vanaf Helshoogte and Simonsberg (beide onderlê deur
graniete), Papegaaiberg and Devon Valley (beide onderlê deur hornfels) was nie betekenisvol
gedomineer deur 'n spesifieke sandfraksie nie. Gronde vanaf hierdie lokaliteite het dus nie
slegs die onderliggende gesteentes verteenwoordig nie. Dit dui op vermenging van
moedermateriaal en/of eoliese prosesse by Helshoogte, Simonsberg and Devon Valley. 'n
Styging in seevlak kon die moedermateriaal by Papegaaiberg beïnvloed het.
Om meer inligting omtrent die oorsprong en moontlike vermening van moedermateriaal voor
grondvorming te verkry, is die verskillende grondmonsters chemies ontleed. Kalium is In
uiters belangrike voedingselement wat lootgroei en wynkwaliteit kan beïnvloed. Aangesien
die gronde in hierdie studie in bestaande produksieblokke voorkom, was daar 'n goeie kans
dat bemestingstowwe die chemiese samestelling kon beïnvloed. Die C horisonte van die
verskillende gronde was beskou as dié wat die minste deur bemesting beYnvloedsou word en
die naaste aanduiding van natuurlike grondchemiese samestelling. Die C horison K-inhoude
van die gronde in die studie het egter nie gekorreleer met enige eienskap wat die
moedermateriaal van die gronde met die lokale gesteentetipe kon verbind nie. By
Durbanville, het beide gronde klein hoeveelhede K in die C horisonte bevat, wat die
onderliggende fillietiese skalies reflekteer, maar by Devon Valley en Papegaaiberg, het die C
horisonte meer K bevat as wat verwag is. Die gronde by hierdie lokaliteite word onderlê deur
hornfels, wat lae hoeveelhede K bevat. Die groot hoeveelhede K in hierdie gronde dui
moontlik op 'n kontaksone tussen graniet en Malmesbury gesteentes in die area. Gronde
vanaf Kuilsrivier, Simonsberg en Helshoogte word onderlê deur K-ryke porfiritiese graniete
wat groot hoeveelhede K in die ondergronde sou bevat. Dit was egter nie die geval nie en dit
was aanvaar dat verdunning van K-arme materiaal plaasgevind het. Die oorsprong van Karme
materiaal was waarskynlik vanaf hoêr-liggende sandstene, of vanaf eoliese prosesse
gedurende die Cenozoikum. Alternatiewelik is K inhoude van die gronde verlaag deur lang
en aanhoudende loging.
'n Semi-kwantitatiewe analise van minerale in die kleifraksie was uitgevoer om te bepaal
watter minerale in die kleifraksie van die verskillende gronde teenwoordig is en om die
minerale met stadia van verwering te vergelyk. Dan kon die mineralogiese samestelling in
verband met moedermateriaal gebring word. Resultate het aangetoon dat al die gronde in die
studie in 'n gevorderde stadium van verwering is en gedomineer word deur kaoliniet, en in
sekere gronde, klei fraksie kwarts. Aangesien die primêre minerale in 'n groot mate
afgebreek is, was dit moeilik om die minerale in die kleifraksie direk in verband met
moedermateriaal te bring. Die voorkoms van kwarts en gibbsiet in die kleifraksie in beide
gronde van Simonsberg, Helshoogte en Durbanville asook een grondvorm vanaf beide
Kuilsrivier en Simonsberg, het aangetoon dat verskillende stadia van verwering gedurende
grondvorming in hierdie gronde voorgekom het. Dit kan die gevolg wees van vermenging van verskillende moedermateriaal, maar kan ook verskillende periodes van verwering van
dieselfde materiaal aandui. Beide gronde by Papegaaiberg, beide gronde van Devon Valley
die ander gronde by Simonsberg en Kuilsrivier het slegs een fase van verwering tydens
grondvorming aangedui, hoofsaaklik as gevolg van die afwesigheid van gibbsiet wanneer
kwarts voorkom.
Grondeienskappe, soos bepaal in hierdie studie, was ook vergelyk met lootgroei, wynkwaliteit
en wynkarakter, soos verkry uit die resultate van die multi-dissiplinêre projek. Vir die meeste
gronde in die studie was 'n toename in kleifraksie kaoliniet geassosieer met afname in
vegetatiewe groei, algemene wynkwaliteit, asook vars vegetatiewe wynkarakter. 'n Toename
in kleifraksie kwarts was geassosieer met hoër algehele wynkwaliteit. 'n Toeneme in
vegetatiewe groei het ook die vars vegetatiewe karakter van die wyn positief beïnvloed. Beter
vegetatiewe groei het op hoër hoogtes voorgekom en dit het gelei tot hoër wynkwaliteit vir
Sauvignon blanc. Wyne afkomstig van wingerde op beide fillietiese skalies en porfiritiese
graniete, was van hoër kwaliteit (Durbanville and Helshoogte), maar beide was geassosieer
met lae kleifraksie kaoliniet en hoë ligging. Dit was nie moontlik om moedermateriaal direk
met vegetatiewe groei, wynkwaliteit en/of wynkarakter te vergelyk nie. Wyne met die laagste
kwaliteit kom egter voor op hornfels (Papegaaiberg and Devon Valley), wat beide groot
hoeveelhede kleifraksie kaoliniet bevat en geleê is op lae hoogtes. Hoê vlakke van K in
gronde wat groot hoeveelhede kleifraksie kaoliniet bevat kan gedeeltelik verantwoordelik
wees vir lae kwaliteit wyne op sulke gronde.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52287 |
| Date | 03 1900 |
| Creators | Van Schoor, Lourens H. |
| Contributors | Lambrechts, J. J. N., Saayman, D., Stellenbosch University. Faculty of AgriSciences. Dept. of Soil Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 113 p. : ill. |
| Rights | Stellenbosch University |
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