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.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The agricultural sector in South Africa relies heavily on the use of pesticides to protect crops against pest organisms. Pesticides can affect non-target organisms such as the meso- and macrofauna in the soil detrimentally. Since these organisms play an important role in the processes of mineralization and decomposition in the soil and contribute to soil fertility, it is important that they are protected. A large amount of published literature exists on the biological importance of soil meso- and macrofauna and the effects that various agricultural practices have on them. The main aim of this study was to investigate the influence of agricultural practices on the abundance and diversity of meso- and macrofauna in different vineyard soils. A comparative study was conducted of an organically managed, conventionally managed and an uncultivated control soil. A secondary aim was to determine the effect of these agricultural management practices on the biological activity of these animals. Soil samples were taken, from which mesofauna (Collembola and Acari) were extracted with a modified Tullgren extractor, identified and counted. Earthworms were extracted from the soil using hand sorting methods. Soil parameters such as pH, water holding capacity, organic matter content, soil texture and soil respiration were determined. Bait lamina and litter-bags were also used to help determine the biological activity within the soil. The mesofauna diversity was quantified using the Shannon Weiner diversity index, as well as a diversity index described by Cancela da Fonseca and Sarkar (1996). Differences in abundance of both the meso-and macrofauna were statistically measured using ANOVA's. Biological activity results were also interpreted using ANOV A's. Results indicate that the abundance of the meso fauna was the highest at the organically treated vineyard soil and lowest in the conventionally managed soil where pesticide application took place. The earthworms also showed the same trend as the mesofauna, but were much more influenced by seasonal changes. Biological activity, according to the bait lamina and the litter-bag results, was higher in both the conventionally and organically managed soils than in the control, but no statistical significant differences were found between the two experimental soils. The soil respiration (C02-flux), also indicating biological activity, was highest in the organically treated soil and lowest in the conventionally treated soil. The different sampling techniques used gave variable results and although the organically managed soil proved to have higher abundances of both meso- and macrofauna, the biological activity did not show the same trends. In conclusion the data did not give enough evidence as to whether organic management practices were more beneficial than conventional management practices for the maintenance of soil biodiversity. / AFRIKAANSE OPSOMMING: Die Suid Afrikaanse Landbousektor steun hewig op die gebruik van verskillende chemiese pestisiede om oeste teen pes organismes te beskerm. Pestisiede kon ook verskeie ander nie-teikenorganismes soos die meso- en makrofauna in die grond negatief affekteer. Hierdie organismes behoort beskerm te word omdat hulle 'n belangrike rol speel in grondprosesse soos mineralisering, en die afbreek van organiese materiaal. Hierdie organismes dra ook by tot die vrugbaarheid van die grond. Daar is heelwat gepubliseerde literatuur beskikbaar wat verband hou met die biologiese belangrikheid van grond meso- en makrofauna en die effekte wat verskeie landbou behandelings op hulle het. Die primêre doel van hierdie studie was om vas te stel watter invloed konvensionele landboupraktyke op die hoeveelheid en diversiteit van meso- en makrofauna in verskillende wingerdgronde het. 'n Vergelykende studie is gedoen om wingerdgronde wat konvensioneel en organies behandel is sowel as 'n onbehandelde kontrolegrond met natuurlike plantegroei met mekaar te vergelyk. 'n Sekondêre doel van hierdie studie was ook om die effek van die verskillende boerderymetodes op die biologiese akitiwiteit in die grond te ondersoek. Grondmonsters is geneem, waaruit die meso fauna (Collembola en Acari) deur middel van 'n aangepaste Tullgren ekstraktor ge-ekstraheer, geïdentifiseer en getel. Die erdwurms is deur middel van handsorteringsmetodes versamel. Die volgende grond parameters is gemeet: pH, waterhouvermoë, organiese materiaal inhoud, grondtekstuur en grondrespirasie. "Bait lamina" en "litter bags" is ook gebruik om biologiese aktiwiteit in die grond te bepaal. Die diversiteit van mesofauna is bepaal met die Shannon Weiner diversiteitsindeks, as ook 'n diversiteitsindeks wat deur Cancela da Fonseca en Sarkar (1996) ontwikkel is. Die resultate van beide die meso- en makrofauna hoeveelhede in die verskillende wingerdgronde is met mekaar vergelyk deur van ANOV A's gebruik te maak. Die resultate van die biologiese aktiwiteit is ook deur middel van ANOVO's statisties met mekaar vergelyk. Die resultate het aangetoon dat die hoeveelheid mesofauna die hoogste in die organies behandelde grond en die laagste in konvensionele grond was. Die erdwurms het dieselfde patroon as die mesofauna getoon, maar is baie meer deur seisoenale faktore geaffekteer, bv. reënval. Volgens die resultate van die "bait lamina" en die "litter bags" was die biologiese aktiwiteit in die grond hoër in beide die eksperimentele grond as in die kontrolegrond. Die grondrespirasie (C02-puIs) was hoër in die kontrolegrond as in die ander eksperimentele gronde. Daar was groot variasie tussen die resultate wat met die verskillende tegnieke verkry is en alhoewel die organiese perseel hoër hoeveelhede van beide meso- en makrofauna gehad het, het die biologiese aktiwiteit nie dieselfde tendens gewys nie. Vanuit die data wat verkry is kon daar dus nie met sekerheid afgelei word dat organiese boerderymetodes beter vir die biodiversiteit van gronde,soos hier gemeet, is as konvensionele boerderymetodes nie.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2007. / This study forms part of an ARC Nietvoorbij research project on the long-term effect of different groundcover management practices in vineyards. This study concentrated on the root distribution of the vines after different groundcover practices were used for one decade. The vineyard on the research farm of the Agricultural Research Council at Robertson, South Africa, was divided into 56 equally distributed trail blocks, 14 treatments with four replicas each. For the study Chardonnay cultivar on 99 Richter rootstock was used. This study concentrated on only eight treatments. The eight different cover crop practices consisted of the mechanical treatment, chemical treatment, straw mulch treatment, permanent cover crop treatment and four annual cover crop treatments. The annual cover crop treatments consisted of triticale cover crop that was sprayed with an herbicide before bloom, a triticale cover crop that was left to die naturally, a grazing vetch cover crop that was sprayed with an herbicide before bloom and a grazing vetch cover crop that was left to die naturally. The vineyard was established in November 1992 while the different treatments started in April 1993. Root studies were conducted during the 2002/2003 season. In this study the auger method was used to determine root density (mm/cm³). The root density was correlated with data from the penetrometer studies, yield and shoot mass collected during the same season.

Thesis (MScAgric)--Stellenbosch University, 1953. / No Abstract Available

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Due to the extraordinary drought resistance of the grapevine, viticulture without irrigation in the winter rainfall coastal areas of South Africa is a feasible and commonly used practice. Wine quality is largely determined by the quality of the grapes from which it is made. Grapevine physiology is affected both directly and indirectly by water stress, which may vary according to soil type and prevailing atmospheric conditions. The water status of the grapevine can affect grape composition profoundly, either directly or indirectly, in either a positive or negative way, depending on the degree as well as the duration of water stress. There are three important factors involved in the development of water stress, namely the transpiration rate, the rate of water movement from the soil to the roots, and the relationship of soil water potential to leaf water potential. All three these factors are affected by atmospheric and/or soil conditions. In warm winelands such as South Africa (Western Cape), with a mediterranean climate which is characterised by a hot, dry summer period, the most important characteristic of soil is its ability to supply sufficient water to the grapevine during the entire growing season. Leaf water potential (Ψl) has gained wide acceptance as a fundamental measure of grapevine water status, and has been widely applied in viticultural research. Shortly before dawn, Ψl approaches equilibrium with soil water potential and reaches a maximum daily value. The study formed an integral part of a comprehensive, multi-disciplinary research project (ARC Infruitec-Nietvoorbij Project No. WW13/01) on the effect of soil and climate on wine quality, which commenced in 1993 and will be completed in 2004. This study was conducted during the 2002/03 growing season in two Sauvignon blanc vineyards situated at Helshoogte and Papegaaiberg, both in the Stellenbosch district, approximately nine kilometres apart. Two experiment plots, representing contrasting soil types in terms of soil water regime, were selected in each vineyard. At Helshoogte the two soils represented the Tukulu and Hutton forms, and the soils at Papegaaiberg were of the Avalon and Tukulu forms. The aim of this study was to determine the effect of atmospheric conditions and soil water status on the level of water stress in the grapevines for each soil at each locality, as well as the effect of grapevine water stress on yield and wine quality. This was done by determining and comparing the soil water status, soil water holding capacity of the soils and the evapotranspiration of the grapevines on the two different soils, at each of the two localities differing in mesoclimate and topography. The atmospheric conditions at the two localities during the 2002/03 season were also determined and compared to the long-term average atmospheric conditions, and the level of water stress of grapevines on each soil at each locality was measured. During the 2002/03 growing season, atmospheric conditions were relatively warm and dry in comparison to the long-term averages of previous seasons. These conditions accentuated the effects of certain soil properties that may not come forward during wetter, normal seasons. The usually wet Tukulu soil at Helshoogte was drier than expected during the 2002/03 season compared to the Hutton soil. Due to more vigorous growth on the Tukulu soil, grapevines extracted more soil water early in the season, leading to a low soil water matric potential and more water stress in the grapevines. Due to the higher vigour, resulting in more canopy shading, and more water stress, the dominant aroma in wines from the Tukulu soil was fresh vegetative. The Hutton soil maintained consistency with regards to both yield and wine quality compared to previous seasons. On the other hand the Tukulu soil supported a higher yield, but with lower than normal wine quality. The Avalon soil at Papegaaiberg maintained the highest soil water potential towards the end of the season, probably due to capillary supplementation from the sub-soil. Grapevines on the Tukulu soil at Papegaaiberg experienced much higher water stress than ones on the other three soils, especially during the later part of the season. This could be ascribed to a combination of factors, the most important being the severe soil compaction at a shallow depth, seriously limiting rooting depth and root distribution, which is detrimental to grapevine performance. Both the soil water status and atmospheric conditions played important roles in determining the amount of water stress that the grapevines experienced at different stages. The air temperature and vapour pressure deficit throughout the season were consistently lower at Helshoogte, the cooler terroir, compared to Papegaaiberg, the warmer terroir. At flowering, Ψl was lower for grapevines at Helshoogte than at Papegaaiberg, showing that diurnal grapevine water status was primarily controlled by soil water content. The difference in grapevine water status between the two terroirs gradually diminished until it was reversed during the post harvest period when Ψl in grapevines at Papegaaiberg tended to be lower compared to those at Helshoogte. The relatively low pre-dawn Ψl at Helshoogte indicated that the grapevines were subjected to excessive water stress resulting from the low soil water content. However, grapevines at Helshoogte did not suffer material water stress (i.e. Ψl < -1.20 MPa) during the warmest part of the day, suggesting that partial stomatal closure prevented the development of excessive water stress in the grapevines. This suggests that low pre-dawn Ψl values do not necessarily imply that grapevines will experience more water stress over the warmer part of the day, or visa versa. This does not rule out the possibility that side-effects of partial stomatal closure, such as reduced photosynthesis, can have negative effects on grapevine functioning in general. These results also suggest that measurement of diurnal Ψl cycles at various phenological stages is required to understand and quantify terroir effects on grapevine water status. / AFRIKAANSE OPSOMMING: Danksy die droogteweerstand van die wingerdstok is die verbouing van wingerde sonder besproeiing ‘n praktiese en algemene verskynsel in die winterreënval-areas van Suid-Afrika. Wynkwaliteit word grootliks bepaal deur die kwaliteit van die druiwe waarvan dit gemaak word. Wingerdfisiologie word direk en indirek beïnvloed deur waterstres, wat kan varieer volgens die grondtipe en die heersende atmosferiese toestande. Die waterstatus van die wingerdstok beïnvloed druifsamestelling, direk of indirek, en positief of negatief, afhangend van die graad en tydsduur van die waterstres. Daar is drie belangrike faktore betrokke by die ontwikkeling van waterstres, naamlik die transpirasietempo, die tempo van waterbeweging vanaf die grond na die wortels, en die verhouding tussen die grondwatermatrikspotensiaal tot blaarwaterpotensiaal. Al drie die faktore word beïnvloed deur die atmosferiese en/of grondtoestande. In warm wynboulande soos Suid-Afrika (Weskaap), met ‘n meditereense klimaat wat gekarakteriseer word deur ‘n warm, droë somerperiode, is die belangrikste eienskap van grond die vermoë om voldoende water aan die wingerdstok te verskaf gedurende die hele seisoen. Blaarwaterpotensiaal (Ψl) het wye aanvaarding bekom as die fundamentele meting van wingerstokwaterstatus, en word wyd toegepas in wingerdkundige navorsing. Kort voor sonsopkoms, nader Ψl ‘n ewewig met die grondwatermatrikspotensiaal en bereik ‘n maksimum daaglikse waarde. Die studie vorm ‘n integrale deel van ‘n omvattende, multi-dissiplinêre navorsingsprojek (ARC Infruitec-Nietvoorbij Projek No. WW13/01) op die effek van grond en klimaat op wynkwaliteit, wat in 1993 in aanvang geneem het en in 2004 afgehandel sal word. Hierdie studie is uitgevoer gedurende die 2002/03 seisoen in twee Sauvignon blanc wingerde geleë by Helshoogte en Papegaaiberg, beide in die Stellenbosch distrik, ongeveer nege kilometer van mekaar. Twee eksperimentele persele, elkeen verteenwoordigend van kontrasterende grondtipes in terme van grondwaterregime, is geselekteer in elke wingerd. By Helshoogte word die twee gronde verteenwoordig deur die Tukulu en Hutton grondvorms, en die gronde by Papegaaiberg is van die Avalon en Tukulu vorms. Die doel van die studie was om die effek van atmosferiese toestande en grondwaterstatus op die wingerdstok se waterstatus vir elke grond by die twee lokaliteite te bepaal, sowel as die effek van die wingerdstok se waterstatus op die opbrengs en wynkwaliteit. Dit is gedoen deur die grondwaterstatus, die grondwaterhouvermoë, sowel as die evapotranspirasie van die wingerdstokke op die twee verskillende gronde by elk van die twee lokaliteite, wat verskil in mesoklimaat en topografie, te bepaal en vergelyk. Die atmosferiese toestande by die twee lokaliteite gedurende die 2002/03 seisoen is ook bepaal en vergelyk met die langtermyn gemiddelde atmosferiese toestande. Die vlakke van waterstres in wingerdstokke op elke grond by elke lokaliteit is ook gemeet. Gedurende die 2002/03 groeiseisoen, was die atmosferiese toestande relatief warm en droog in vergelyking met die langtermyn gemiddeldes van vorige seisoene. Hierdie kondisies aksentueer die effek van sekere grondeienskappe wat nie noodwendig na vore kom gedurende normale, natter seisoene nie. Die gewoonlike nat Tukulu grond by Helshoogte was droër as verwag gedurende 2002/03 in vergelyking met die Hutton grond. As gevolg van sterker groekrag op die Tukulu grond, het wingerdstokke meer grondwater onttrek vroeg in die seisoen, wat gelei het tot ‘n lae grondwatermatrikspotensiaal en meer waterstres in die wingerdstokke. Die sterker groeikrag het meer beskaduwing van die lower asook meer waterstres veroorsaak, wat gelei het daartoe dat die dominante aroma in wyne vanaf druiwe op die Tukulu grond vars vegetatief was. Die Hutton grond het bestendig gebly in terme van opbrengs en wynkwaliteit in vergelyking met vorige seisoene. Daarteenoor het die Tukulu grond ‘n hoër opbrengs gelewer, maar met laer as gewoonlike wynkwaliteit. Die Avalon grond by Papegaaiberg het die hoogste grondwatermatrikspotensiaal behou tot die einde van die seisoen, heelwaarskynlik a.g.v. kapillêre aanvulling vanuit die ondergrond. Wingerdstokke op die Tukulu grond by Papegaaiberg het heelwat meer waterstres ondervind as op die ander drie gronde, veral later in die seisoen. Dit kan toegeskryf word aan ‘n kombinasie van faktore, die belangrikse daarvan die erge grondkompaksie vlak in die grond, wat worteldiepte en -verspreiding ernstig beperk het, wat op sy beurt nadelig is vir wingerdprestasie. Beide die grondwaterstatus en atmosferiese toestande het ‘n belangrike rol gespeel in die bepaling van die hoeveelheid waterstres wat die wingerdstok op verskillende stadiums ondervind het. Die lugtemperatuur en waterdampdruktekort was regdeur die seisoen laer by Helshoogte, die koeler terroir, as by Papegaaiberg, die warmer terroir. Gedurende blom was die Ψl laer vir wingerdstokke by Helshoogte as by Papegaaiberg, wat daarop wys dat daaglikse wingerdstok waterstatus hoofsaaklik deur die grondwaterinhoud bepaal was. Die verskil in wingerdstok waterstatus tussen die twee terroirs het geleidelik verminder totdat dit omgekeer was gedurende die na-oes periode toe Ψl in wingerdstokke by Papegaaiberg geneig het om laer te wees in vergelyking met die by Helshoogte. Die relatiewe lae voorsonop Ψl by Helshoogte het daarop gedui dat die wingerdstokke aan oormatige waterstres onderwerp was. Die wingerdstokke by Helshoogte het egter nie materiële waterstres (i.e. Ψl < -1.20 MPa) gedurende die warmste gedeelte van die dag ondervind nie, wat aandui dat gedeeltelike huidmondjiesluiting plaasgevind het om die ontwikkeling van oormatige waterstres te verhoed.Dit dui aan dat lae voorsonop Ψl waardes nie noodwendig impliseer dat wingerdstokke meer waterstres gedurende die warmste gedeelte van die dag sal ondervind nie, of visa versa. Dit sluit nie die moontlikheid uit dat negatiewe neweeffekte van gedeeltelike huidmondjiesluiting, soos ‘n vermindering in fotosintese, ‘n negatiewe effek kan hê op die wingerdstok se funksionering in die algemeen nie. Hierdie resultate stel voor dat die meting van daaglikse Ψl siklusse gedurende verskeie fenologiese stadia benodig word om die effek van terroir op die wingerdstok se waterstatus te verstaan en te kwantifiseer.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2005. / This thesis forms part of a research program that is investigated by ARC Infruitec- Nietvoorbij and the University of Stellenbosch. The aim of this program is to quantify the effect of soil and climate on wine quality and character as a basis for scientific demarcation of production regions. Natural factors are first quantified and characterised so that relative homogeneous natural terroir units (NTU) can be identified. Thereafter wines made from these different localities are assessed for similarities which permit grouping of localities into viticultural terroirs. The present study involved seven research plots in the Robertson district, making use of initial measurements by ARC Infruitec-Nietvoorbij in the 2000/01 and 2001/02 seasons together with more intensive measurements in the 2002/03 and 2003/04. The seven plots are located in two wards, Le Chasseur and Vinkrivier. Sauvignon blanc plots were marked at two localities, each with two sub-plots occurring in one block. Three Cabernet Sauvignon plots were marked out. Two plots occurred in one block in Le Chasseur and one plot in Vinkrivier. Plots within the same block were located on different soil types so that the effect of soil type on wine quality and character could be monitored. Morphological examination of soil profiles at each plot was carried out together with physical and chemical analysis of samples taken at 30cm depth intervals. Soil water content was measured at regular intervals to assess soil water tension. Vineyard performance was assessed in terms of phenology, root system studies, leafwaterpotential measurements, canopy quality assessment, leaf analysis, shoot growth, and data relating to ripening, harvest and pruning. Wines were made from each plot by ARC Infruitec- Nietvoorbij and evaluated by a tasting panel after six months and then again after eighteen months. Meteorological data were collected in each ward.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Little scientific information regarding the effect of different geological parent materials on grapevine performance is currently available in South Africa. This aspect is of special significance for the Helderberg area, where parent material may change from granite to shale over a short distance. This results in shale- as well as granite-derived soils often occurring within the same vineyard. The objectives of this study were to (i) quantify the nutritional status and other soil properties of different parent materials (shale and granite) and overlying soils (ii) investigate the impact of geological differences in the soil on the vine nutritional status and certain vine parameters. This study was done over two seasons (2006/2007 and 2007/2008). Two Sauvignon blanc and two Cabernet Sauvignon vineyard blocks were selected at two different localities for each cultivar in the Helderberg area, South Africa. Shale- and granitederived soils were identified within each block. Kaolinite was the dominant mineral, whereas quartz and feldspar were sub-dominant. Traces of mica were also present in some shale- and granite-derived soils. Granite- contained significantly higher contents of coarse sand than shale-derived soils, whilst the opposite occurred in terms of fine sand. These differences affected the water holding capacity, in general making it higher in shale- than granite-derived soils. Shale-derived soils had higher concentrations of total K but granite-derived soils had a higher ability to release K as they contained higher concentrations of soluble K. The Q/I parameters, potential buffering capacity of K (PBCK) and equilibrium activity ratio of K (ARK) showed no consistent responses to geological differences. Potassium concentrations were higher in the leaf blades (obtained before harvest in 2007) from Sauvignon blanc grapevines on granite- than on shale-derived soils. Potassium concentrations in the Cabernet Sauvignon juice (obtained in 2007) tended higher in juice from granite- than from shale-derived soils. In 2008, K concentrations tended higher in juice from shale- than from granite-derived soils for both cultivars. The pH of the Sauvignon blanc juice (obtained in 2008) tended higher in juice from shale-than from granite-derived soils, thus corresponding with the K concentrations in the juice in this season. Nitrogen concentrations were higher in Cabernet Sauvignon juice (obtained in 2007) and Sauvignon blanc juice (obtained in 2008) from shalethan from granite-derived soils. In terms of vine water status, vines on granite-derived soils appeared more stressed than those on shale-derived soils in both seasons at one of the vineyards. In these Sauvignon blanc and Cabernet Sauvignon vineyards, the K nutritional status was not affected by geology in a consistent manner but there were some noticeable tendencies for a specific cultivar during certain seasons. On account of vines being planted on shale- and granite-derived soils within the same block, soil preparation was done similarly for both soils, and they were exposed to similar irrigation schedules, canopy management strategies and climatic conditions. Therefore, there is a high probability that all these practices may have negated the effect of geology on the K status of soils and especially on juice K concentration at the time of harvest. It was clear that seasonal differences and fertilisation affected the nutritional status of the vines more than geology. / AFRIKAANSE OPSOMMING: In Suid-Afrika is daar tans min wetenskaplike inligting oor die effek van verskillende geologiese moedermateriale op die prestasie van wingerd beskikbaar. Hierdie aspek is veral van belang in die Helderberg-area, waar moedermateriaal oor ‘n baie kort afstand van graniet na skalie kan wissel. Dit lei daartoe dat skalie-, sowel as granietgronde, dikwels binne dieselfde wingerd voorkom. Die doelwitte van die studie was om: (i) die voedingstatus en ander grondkundige eienskappe van die verskillende moedermateriale (skalie en graniet) en oorliggende gronde te kwantifiseer (ii) die impak van geologiese verskille in die grond op wingerd se voedingstatus en sekere wingerdkundige parameters, te ondersoek. Hierdie studie is oor twee seisoene (2006/2007 en 2007/2008) gedoen. Twee Sauvignon blanc en twee Cabernet Sauvignon wingerdblokke is geselekteer by twee verskillende lokaliteite vir elke kultivar in die Helderbergarea, Suid-Afrika. Beide skalie- en granietgrond is binne elke blok geïdentifiseer. Kaoliniet was die dominante mineraal, met kwarts en veldspaat sub-dominant, terwyl spore van mika ook in beide skalie- en granietgronde gevind is. Granietgronde het betekenisvol hoër hoeveelhede growwe sand bevat, terwyl skaliegronde meer fyn sand bevat het. Hierdie verskille het ‘n effek op waterhouvermoë gehad en daartoe gelei dat waterinhoude oor die algemeen hoër was vir skaliegronde. Skaliegronde het groter hoeveelhede totale K bevat, maar granietgronde se vermoë om K vry te stel was hoër, omdat hulle ‘n hoër konsentrasie oplosbare K bevat het. Die Q/I parameters, potensiële buffervermoë vir K (PBCK) en ewewig aktiwiteitsverhouding vir K (ARK), is nie op ‘n konsekwente wyse deur geologiese verskille beïnvloed nie. Vir die Sauvignon blanc wingerde was kalium konsentrasies in blaarskywe (gemonster voor oes in 2007) hoër vir graniet- as vir skaliegronde. Kalium konsentrasies in die sap vanaf Cabernet Sauvignon (gemonster in 2007) het hoër geneig vir granietgronde. In 2008 het die kalium konsentrasies, vir beide kultivars, hoër geneig in sap vanaf skaliegronde. Gedurende dié seisoen het die pH van sap ook hoër geneig vir Sauvignon blanc vanaf skaliegronde, wat dus ooreenstem met die K inhoud van die sap. Stikstof konsentrasies was hoër in sap vanaf skaliegronde vir Cabernet Sauvignon (2007) en vir Sauvignon blanc (2008). In terme van die wingerde se waterstatus, het stokke op die granietgrond, by een van die lokaliteite, geneig om gedurende beide seisoene onder groter stremming te wees op graniet as op skaliegrond. In hierdie Sauvignon blanc en Cabernet Sauvignon wingerde, is K voedingstatus nie op ‘n konsekwente wyse deur geologie geaffekteer nie, maar gedurende sommige seisoene was daar wel duidelike tendense vir ‘n spesifieke kultivar. Omdat die stokke binne dieselfde blok op skalie- en graniet gronde geplant is, was grondvoorbereiding eenders vir die twee grondtipes terwyl besproeiingskedule, lowerbestuur en klimaatstoestande ook identies was. Daar is dus ‘n hoë waarskynlikheid dat al hierdie faktore daartoe kon bygedra het dat die effek van geologie op die K status van van gronde versluier is, veral die effek op die K inhoud van sap teen oestyd. Dit was duidelik dat seisoenale klimaatsverskile en bemestingspraktyke ’n groter effek as geologie op die voedingstatus van die wingerd gehad het.