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.

Thesis (MScAgric)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: In the past it was very difficult to visualise the extent and distribution of variability in growth vigour within vineyards. The advancement of remote sensing technology has changed this however, establishing new methods to assess and manage variability. Even though the causes and effects of within-vineyard variability in growth vigour are complex, new technologies offer better ways of monitoring, researching and managing these factors. In addition to the possible benefits of aerial or satellite remote sensing, new methods of mapping soil spatial variability as well as advances in georeferencing technologies supply precision tools to both researchers and producers. The scientific advancement of the technology, however, is currently the most important aspect needed. This is crucial to answer and explore fundamental questions regarding the use of the technology and the interpretation of results within the framework of the plant's observed reaction. Only then can the possible applications in vineyard management be optimised to address the management problems of extensive within-vineyard variation in growth vigour. The choice will always be to use the technology to manage the observed variability in order to limit the negative impacts of a heterogeneous harvest, or to identify the variability and its causes for the implementation of management practices aimed at a more homogenous vineyard and harvest. Whatever the case, extensive research is needed to provide tight correlations between information gathered with new technologies to assess variability and plant status, such as multi- and hyperspectral analysis, and ground-truthed results in the vineyard. Only then will it become evident which methods and analyses would be useful in the drive towards in-depth analysis and management of vineyards within the concept of precision viticulture and its derived advantages. With this in mind, the aim of this study was to establish an experimental model to use remote sensing technologies to identify and classify within vineyard variability with a subsequent analysis of the causes of variability and the effects on the plants. The targeted experimental model was a vineyard with highly heterogeneous above-ground growth. An aerial photograph of the vineyard was studied and manipulated to yield image pixel values used to quantify the degree of variability for different plots, which were chosen according to different plot layouts. Soil conditions were assessed on both a global and plot level, with extremely high pH and low resistance values in the soil in combination with erratic soil preparation practices found to be the main cause of variability. Soil physicochemical condition was also assessed during a soil profile pit study. Significant differences were found between several soil-related parameters measured for the higher and lower vigour levels and a strong correlation was also found between the resistance of a saturated soil paste and the image pixel values. Vegetative measurements also yielded highly significant differences between the vigour levels and confirmed the suitability of the vineyard to study within-vineyard variability. Some of these measurements were also strongly correlated with soil conditions as well as image pixel values. Trunk circumference proved to be an excellent measure for the level of variability, being linked strongly to canopy characteristics, soil conditions as well as the image pixel values. Leaf water potential measurements also yielded significant differences between the vigour levels. Harvest data and wine analyses showed the effect that vigour differences can have on grape composition and wine quality, even though the differences found here were much less than expected. Even though no clear preference was shown between the wines made from the different vigour levels, the lower vigour wine was considered fruitier. The overall quality of both experimental wines was however very high, considering that experimental winemaking techniques has been used. Hyperspectral measurements also confirmed differences between the vigour levels through a narrow-band NOVI (normalised difference vegetation index). It was also possible to show differences in certain biochemical compounds between the vigour levels on both a leaf and canopy level. Wavelength regions corresponding to carotenoid, chlorophyll a and chlorophyll b showed different spectral reactions in the leaves of more stressed (lower vigour) canopies, indicating possibilities for further studies. This study and its results is the first of its kind in the South African wine industry and paves the way for more focussed and in-depth analyses of the use of specifically multiand hyperspectral data to accurately assess within-vineyard vigour variability and the management thereof to yield optimum quality grapes for a specific wine target. Moreover, the approach adopted in this study is also echoed in other international research programs in prominent wine countries. The availability of scientific research regarding the optimal use and limitations of these technologies has the potential to revolutionise production management practices in the next few years in the viticultural industry. / AFRIKAANSE OPSOMMING: In die verlede was dit baie moeilik om die omvang en verspreiding van groeikragvariasie binne 'n wingerd te visualiseer. Die vordering gemaak op die gebied van afstandswaarneming-tegnologie het egter nuwe metodes beskikbaar gestel waardeur hierdie variasie in wingerde gemonitor en bestuur kan word. Selfs al is die oorsake en invloede van binne-wingerd-groeikragvariasie kompleks, verskaf nuwe tegnologieë verbeterde metodes om hierdie variasie te monitor, te bestuur en na te vors. Saam met die moontlike voordele wat lugfoto's en satelliet-afstandswaarneming teweegbring, verskaf nuwe metodes om ruimtelike variasie in grondfaktore te karteer, asook vordering in geoverwysingstegnologie, presisiehulpmiddels aan produsente én navorsers. Die wetenskaplike vordering van dié tegnologie is tans van groot belang. Die belang daarvan is om fundamentele vrae te ondersoek en te beantwoord rakende die gebruik van die tegnologie en die interpretasie van resultate binne die raamwerk van die waargeneemde reaksie in die plant. Dit sal die weg baan vir optimale toepassing van die tegnologie in wingerdbestuur om sodoende die bestuursprobleme wat deur binne-wingerdgroeikragvariasie teweeggebring word, aan te spreek. Die voorkeurkeuse is om dié tegnologie aan te wend om hierdie variasie te bestuur sodat die negatiewe impak van In heterogene oes teengewerk kan word, of om die variasie te identifiseer vir die implementering van bestuurspraktyke gemik op die skep van 'n meer homogene wingerd en oes. Dit is noodsaaklik dat uitgebreide navorsing gedoen word om noue verwantskappe vas te stel tussen inligting wat ingewin is met behulp van nuwe tegnologieë wat die variasie in plantstatus monitor, soos multi- en hiperspektrale analise, en inligting wat op grondvlak ingewin is. Hieruit sal dit duidelik wees watter metodes en analises die doeltreffendste is vir in-diepte analises en die bestuur van wingerde binne die konsep van presisie-wingerdkunde. Met inagneming van hierdie aspekte, was die doel van hierdie studie om 'n eksperimentele model daar te stel waardeur afstandswaarneming-tegnologie gebruik kan word om variasie binne wingerde te identifiseer en te klassifiseer deur analises van die oorsake van hierdie variasie en invloede op die plant. Die geteikende eksperimentele model was 'n wingerd met hoogs heterogene bogrondse groei. 'n Lugfoto van die wingerd is bestudeer en gemanipuleer om pixelwaardes te verskaf wat die graad van variasie vir verskillende eksperimentele plotte, wat aan die hand van verskillende plotuitlegte gekies is, te kwantifiseer. Grondtoestande is bestudeer op 'n globale én plotvlak, met uiters hoë pH en lae weerstande in kombinasie met verkeerde grondvoorbereidingspraktyke, wat geïdentifiseer is as die hoofoorsake vir die hoë vlakke van variasie. Grondfisiese en -chemiese toestand is ook tydens profielgatstudies bestudeer. Betekenisvolle verskille is gevind tussen verskeie grondverwante parameters gemeet vir plotte met onderskeidelik laer en hoër groeikrag, en 'n sterk verwantskap is gevind tussen grondweerstand en pixelwaardes, soos vanaf die lugfoto bepaal. Vegetatiewe metings het ook betekenisvolle verskille tussen die hoër en laer groeikragvlakke opgelewer, wat die geskiktheid van die wingerd vir die studie van binnewingerdvariasie in groeikrag bevestig het. Van hierdie metings was ook nou verwant aan grondtoestande, asook beeldpixelwaardes. Stamomtrek was 'n uitstekende maatstaf vir die vlakke van variasie, aangesien dit nou verwant was aan lowertoestande, grondtoestande, asook beeldpixelwaardes. Blaarwaterpotensiaal-metings het ook betekenisvolle verskille tussen die hoër en laer groeikragvlakke opgelewer. Oesdata en wynanalise het die uitwerking van groekragverskille op druifsamestelling en wynkwaliteit uitgewys, selfs al was die verskille wat gevind is minder as wat verwag is. Hoewel geen duidelike voorkeur tussen die wyne afkomstig van verskillende groeikragvlakke uitgewys kon word nie, was die wyn wat van die laer-groeikrag stokke gemaak was, meer vrugtig. Die algemene kwaliteit van beide wyne was egter baie hoog as in ag geneem word dat eksperimentele wynmaakprosedures gevolg is. Hiperspektrale metings het ook die verskille tussen groeikragvlakke bevestig deur 'n nou-bandwydte NDVI ("normalised difference vegetation index"). Dit was ook moontlik om verskille in sekere biochemiese komponente tussen die groeikragvlakke op 'n blaar- én lowervlak uit te wys. Golflengte-areas ooreenstemmend met karotenoïed, chlorofil a en chlorofil b het verskillende spektrale reaksies in die blare met hoër stresvlak (laer groeikrag) lowers ten toon gestel. Dit het moontlikhede vir verdere navorsing uitgewys. Hierdie studie en die resultate wat verkry is, is die eerste van sy soort in die Suid- Afrikaanse wynbedryf. Dit baan die weg vir meer gefokusde en in-diepte analise van die gebruik van spesifiek multispektrale en hiperspektrale data om binne-wingerdgroekragvariasie akkuraat te monitor en te bestuur met die oog op optimum wynkwaliteit vir 'n spesifieke produkdoelwit. Die aanslag van hierdie navorsing is ook sigbaar in ander prominente wynproduserende lande. Beskikbaarheid van wetenskaplike navorsing rakende die optimale gebruik en tekortkominge van hierdie tegnologieë het die potensiaal om produksiebestuurspraktyke in die wingerdbedryf in die komende jare te revolusionaliseer.

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 (PhD(Agric) (Agronomy))--University of Stellenbosch, 2007 / A selection of species suitable for cover crop management in the different wine grape regions is required to enable more producers to apply this environment friendly practice in a sustainable manner as part of an integrated production strategy. The correct management practice(s) to be applied to these species over both the short and long term in a cooler and warmer wine grape region needed clarification. The effect of seeding date on the dry matter production (DMP) and weed control efficacy of seven grasses and sixteen legumes, as well as varieties of three of these species, was determined during 1991 and 1992. The decomposition rate of the mulches was determined. In the cooler climate of Stellenbosch (33o55'S, 18o52'E), the Medicago species, subterranean clovers, pink Seradella and three Vicia species did not compete effectively with the winter weeds if the weekly precipitation from mid-March to mid-May (autumn) exceeded 18 mm. The two oat species, as well as rye and triticale produced more than five t/ha of dry matter if the precipitation exceeded 18 mm per week. The DMP of the above-mentioned species indicated that these species could be considered for cover crop management in Lutzville (31o35'S, 18o52'E), if full surface irrigation of 18 mm per week could be applied for 10 weeks directly after sowing, followed by 18 mm fortnightly. Seeding date had a significant effect on DMP in both regions. A highly significant correlation (r = 0.85, p ≤ 0.0001) existed between the decomposition rate of the mulches and the initial amount of dry matter present on the soil surface.

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In an attempt to reduce the pH of juice and wine, different fertiliser applications and canopy management practices were evaluated in a field trial. Fertiliser treatments consisted of no, CaS04, Ca(OH)2, and MgS04 fertilisation. Canopy management was as follows: suckering (leaving only two shoots per bearer), tipping, vertical shoot positioning and removal of lateral shoots and yellow leaves in the bunch zone (Canopy 1); suckering (leaving three shoots per bearer), vertical shoot positioning as well as topping (Canopy 2); vertical shoot positioning and topping (Canopy 3). The field trial was conducted in the Paardeberg region on the farms Meerlus and Kersfontein. The vineyard at Meerlus was Cabernet franc/R99 with a high canopy density and a good root distribution, established on a sandy loam soil of granite origin, with a low subsoil pH and a high K content. The vineyard at Kersfontein was Cabemet Sauvignon/101-14 Mgt with a lower canopy density and a less extensive root distribution, also established on a sandy loam soil of granite origin, but with a low top- and subsoil pH and a higher K content. Fertilisation had no significant influence on the K content of juice and wine. Fertilisation with Ca and Mg reduced the pH of juice significantly in the case of Meerlus. In contrast, Mg fertilisation increased the pH of juice significantly at Kersfontein. Lastly, fertilisation had no significant effect on the pH of the wine. The K content of the juice at Meerlus was significantly reduced by Canopy 3 in comparison with Canopy 1 and 2. However, in contrast with Canopy 1 and 3, Canopy 2 significantly increased the pH of juice at Meerlus. The K content of the juice at Kersfontein was significantly reduced by Canopy 1, compared to Canopy 2 and 3, with no significant effect on the pH of the juice. Canopy management had no significant effect on wine pH. It appears to be possible to reduce the pH of juice in the case of Cabernet franc/99R, situated on granite soils, by means of Ca and Mg fertilisation. Because Ca(OH)2 and MgS04 fertilisation increased the maturity of Cabernet Sauvignon/101-14 Mgt grapes, it was impossible to evaluate the effect of fertilisation on the pH of juice at Kersfontein. The general phenomenon that a high canopy density results in a high pH of juice and wine, was not observed in this field trial. The possible reasons for this were the low canopy density of the control plots, as well as the difference in maturity between canopy management treatments. / AFRIKAANSE OPSOMMING: In 'n poging om die pH van sap en wyn te verlaag, is die effek van verskillende bemesting- en lowerbestuursfaktore in 'n veldproef geêvalueer. Bemesting het bestaan uit geen, CaS04, Ca(OH)2 en MgS04 toediennings. Lowerbestuur was: suier tot twee lote per draer, tip, vertikale lootposisionering, verwydering van sylote en geel blare in trossone (Lower 1); suier tot drie lote per draer, top en vertikale lootposisionering (Lower 2); top en vertikale lootposisionering met geen suier nie (Lower 3). Die veldproef is op twee plase nl. Meerlus en Kersfontein, in die Paardeberg omgewing uitgevoer. Die wingerd by Meerlus was Cabernet franc/R99 met 'n hoë lowerdigtheid en goeie wortelverspreiding, wat op 'n sandleemgrond van graniet oorsprong met In lae ondergrond-pH en hoë K-inhoud gevestig is. Die wingerd by Kersfontein het bestaan uit Cabernet Sauvignon/101-14 Mgt met 'n laer lowerdigtheid en swakker wortelverspreiding, wat op In sandleemgrond van graniet oorsprong met In deurgaans lae grond-pH en baie hoë K-inhoud gevestig is. Bemesting het geen betekenisvolle invloed op die K-inhoud van sap en wyn gehad nie. By Meerlus het Ca- en Mg-bemesting egter die pH van sap betekenisvol verlaag. In teenstelling hiermee het Mg-bemesting die sap-ph by Kersfontein betekenisvol verhoog. Bemesting het verder geen betekenisvolle invloed op die pH van wyn gehad nie. Lower 3 het die K-inhoud van sap by Meerlus betekenisvol verlaag in vergelyking met Lower 1 en Lower 2. By Kersfontein was die K-inhoud van sap by Lower 1 betekenisvollaer as by Lower 2 en Lower 3. Teenoor Lower 1 en Lower 3 het Lower 2 'n betekenisvol hoër sap-pH by Meerlus tot gevolg gehad. Lowerbehandelings het egter geen betekenisvolle invloed op die pH van wyn gehad nie. Die moontlikheid bestaan dus om die sap-pH van Cabernet franc/R99 op granietgrond betekenisvol m.b.v. Ca- en Mg-bemesting te verlaag. Aangesien Ca(OH)2- en MgS04- bemesting die rypheidsgraad van Cabernet Sauvignon/101-14 Mgt se druiwe betekenisvol verhoog het, was dit onmoontlik om die effek van bemesting op sap-pH by Kersfontein te evalueer. Die algemene verskynsel dat 'n hoë lowerdigtheid tot hoë pH's in sap en wyn lei, is nie in die proef ondervind nie. Die lae lowerdigtheid van die kontrole persele en die verskil in rypheidsgraad tussen lowerbehandelings kan moontlik as rede hiervoor aangevoer word.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / A common phenomenon in most South African vineyards, especially in the Western Cape region, is that of within vineyard variation. This variation phenomenon is caused by an array of controllable and non-controllable factors that interact with each other to affect vine vigour. Controllable factors can be managed by the grape grower, while the non-controllable factors have to be managed in the planning process in order not to negatively affect productivity or product quality. The main goal of any grape grower is to optimise vine performance in an attempt to achieve the best possible yield while at the same time allowing vines to optimally ripen grapes towards optimal wine quality. A grape grower has to use every possible means and technique available to him in order to manage his vineyards in such a manner as to achieve this goal. In the past, it was difficult to visualize the extent and distribution of vigour variation in vineyards, but with modern technological improvements in the field of remote sensing, grape growers are able to identify and specify different vigour levels within a vineyard. When remote sensing is applied in a vineyard, the grape grower can identify certain areas that may need more specific attention than others. Consequently, managerial decisions based on detailed information can be made in an attempt to improve the general condition and performance of a vine. Not only can the acquired information be used to plan managerial actions throughout the season, but it can also be used to plan and devise harvest strategies. Some areas in a vineyard may be at a certain point in the ripening process and need to be harvested, while grapes from other areas still need to develop the wanted flavours. One managerial action applied at véraison by some grape growers, is that of crop thinning. Different vigour areas can now be subjected to various crop thinning actions in an attempt to determine the best crop load for a vigour level. With this in mind, two studies were launched to firstly investigate the interaction between vine vigour and harvest dates; and secondly to investigate the interaction between vine vigour and crop load and how their combined interaction might influence a vine’s characteristics, grape composition and wine quality. Vigour variation was firstly identified through multispectral aerial imagery, and then visually verified by visits to the experimental vineyards. The multispectral aerial image was then “orthorectified” in order to produce a classified multispectral image. The image was classified through different colour codes that were assigned to the different vigour levels to clearly distinguish between them. A series of vegetative and reproductive measurements were conducted to try and establish if any correlations could be obtained of the interaction between vine vigour, different harvest dates and crop loads. In order to verify differences in vine vigour, underlying causes were also determined through soil analyses of which chemical analysis, bulk density, porosity, as well as root penetration and distribution were determined. Vegetative measurements that were conducted for both studies indicated good correlations between the different vigour levels and the image classifications. The results also identified the effect that topping (mechanical or manual) had on the main and lateral leaf areas. Reproductive measurements throughout the season, in the form of berry sampling, showed changes in berry composition and accentuated the effects of the different treatments, which could also be confirmed through sensorial analysis of the wines. The results also emphasized the need to not only make use of one of two chemical parameters to identify grape ripeness, but to incorporate a number of parameters, such as sugar, pH and acid levels. From the varying grape chemical characteristics, a wine style can be identified that might carry the approval of the winemaker for the production of a specific type of wine. Soil studies of both vineyards also gave important evidence for the causes of vigour variation. The data collected will hopefully provide grape growers with information that will enable them to make educated decisions concerning grape production and how vigour, in conjunction with different harvest dates and crop loads, will enable them to produce fruit of good quality and, so doing, improve their financial position.

Thesis (MSc)--Stellenbosch University, 1955. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Food demands for the ever-increasing human population is increasing the pressure on the agricultural sector to produce more food. In order to satisfy these demands, farmers are turning to chemical biocides for the control of pest species to produce greater crop yields. All pesticides must be toxic or poisonous to the target species they intend to control. Unfortunately, most pesticides are toxic or poisonous to non-target organisms as well, with detrimental effects on their health. Organic farming was developed to enhance the overall health of the farm's natural soilmicrobe- plant-animal biodiversity. No synthetic fertilisers and/or pesticides are used when farming organically. Life in the soil consists of intricate food webs and interactions between the soil dwelling invertebrates. The soil-organisms are divided into three main groups, viz., Micro-organisms (e.g. protozoa, bacteria and fungi) mesofauna (nematodes, Collembola and Acari) and macro-fauna (e.g. millipedes, isopods, insects, molluscs and earthworms). The invertebrates are very susceptible to chemical contamination by chemical biocides in natural and agro-ecosystems. The soil invertebrate communities are responsible for the decomposition of organic material in soil, thereby remineralising the soil. The decomposition processes start with comminution of the large pieces of organic material by meso- and macro-fauna and ends with the micro-fauna and microbial organisms that complete these processes by returning the nutrients in an inorganic form to the soil. The aim of this study was to investigate whether, and to what extent the soil organisms are influenced by different management practices viz., organic management practices versus conventional management practices. A vineyard on the farm Plaisir de Merle, in Simondium, Western Cape was used for the present study. One half of a one hectare vineyard was managed organically and the other half conventionally. Within each vineyard block six different treatments were performed. Three of the treatments were strictly organic and the other three were strictly conventional. Four replicates of each management treatment were performed. The bait-lamina technique was used to assess the feeding activity of the soil organisms exposed to the different management treatments. In addition to the bait-lamina trials in the vineyard itself, bait-lamina tests were performed in microcosm studies with soil from the organically and conventionally managed vineyard blocks under controlled conditions. In order to assess the impact of the various pesticides that are used in the vineyards in the conventional way, on the soil fauna, standard acute toxicity tests and behavioural tests were performed on Eisenia fetida, the compost worm. The bait-lamina tests in the vineyard revealed that the moisture content of the soil plays an important role in the biological activity of soil fauna. The different management treatments did affect the biological activity of the soil fauna, but seasonal changes also proved to be one of the important factors governing biological processes in the soil. The acute toxicity tests showed that the active ingredients (mancozeb, penconazole and trifloxystrobin) of three of the pesticides that were tested in this study, had negatively affected E. fetida at their recommended application concentrations. The remaining two pesticides' active ingredients (glyphosate and N-acetyl salicylic acid) did not affect the earthworms negatively at the recommended application concentrations. The preference behavioural trials showed that E. fetida could detect and avoid contaminated substrates at the LCso-concentrations of the different pesticides. All the earthworms were influenced positively in the preference behaviour experiments. Because of certain limitations of the bait-lamina technique, it was difficult to formulate conclusions on what happens in the soil. A possible explanation for the differences in feeding activity of soil fauna could be attributed to the migration of the soil fauna to more habitable soil horizons during the dry summer conditions, when most of the pesticides are applied. The ecological relevance of the acute toxicity tests conducted need to be investigated further. It is clear that the acute toxicity tests provided important information that should be considered, but care should be taken and the necessary safety factors be determined and considered when doing risk assessment studies. The results of the preference behaviour studies showed that for certain pesticides E. fetida can be a sensitive bioindicator of acute and/or sub-acute lethal toxicity testing but this might not necessarily be the case for other pesticides. The goal of doing laboratory studies is to gain as much information to make reliable extrapolations to field situations from laboratory data. Laboratory-to-field extrapolations are very complicated because of the physico-chemical composition of soil, the unpredictable way pesticides behave within soil and the reaction of soil organisms to the soil and to the chemical biocides that are used. Further studies need to be done in order to fully understand to what extent the soil fauna were affected by the different management practices applied to the vineyard at Plaisir de Merle. / AFRIKAANSE OPSOMMING: Voedsel aanvraag vir die toenemende menslike bevolking plaas groot druk op die landbou sektor om meer kos te produseer. Om aan die voedsel eise te voldoen, gebruik boere al meer chemiese biosiede om pesspesies te bestry. Alle pestisiede moet toksies of giftig wees vir die teiken organisme waarvoor dit bestem is. Ongelukkig is die meeste pestisiede ook toksies of giftig vir nie-teiken organismes, wat tot nadelige effekte op hul gesonheid kan lei. Organiese boerdery is ontwikkel om die algehele gesondheid van die plaas se natuurlike grond-mikrobe-plant-dier biodiversiteit te bevorder. Geen sintetiese bemestingstowwe en/of pestisiede mag gebruik word wanneer daar organies geboer word nie. Die lewe in die grond bestaan uit ingewikkelde voedselwebbe en interaksies tussen die grondlewende invertebrate. Die grond invertebrate word verdeel in drie hoof groepe, nl. mikro-organismes (bv. Protozoa, bakterieë en fungi) meso fauna (Nematoda, Collembole en Acari) en makrofauna (bv. Millipoda, Isopoda, Insecta, Mollusca en erdwurms). Die Invertebrata is die mees vatbaarste vir chemiese kontaminasie deur chemiese biosiedes in natuurlike en landbou ekosisteme. Die grond invertebraat gemeenskappe is verantwoordelik vir die afbreek van alle organiese materiaal in die grond en dus vir remineralisering van die grond. Die afbreekproses begin by die komminusie van groter stukke organiese materiaal deur die meso- en makrofauna en eindig met die mikrofauna en mikrobes wat die prosesse voltooi deur die nutriente terug te plaas in die vorm van anorganiese produkte in die grond. Die doel van hierdie studie was om te ondersoek of, en tot watter mate, grond organismes geraak word deur verskillende grondbestuurspraktyke, nl. Organiese grondbestuurspraktyke teenoor die konvensionele grondbestuurspraktyke. 'n Wingerd op die plaas Plaisir de Merle, in Simondium, Wes-Kaap, was gebruik vir die huidige studie. Een helfte van 'n een hektaar wingerd is organies bestuur en die ander helfte is op die konvensionele manier bestuur. Op elk van die twee wingerd blokke is ses verskillende behandelings toegepas. Drie van die behandelings was streng organies en die ander drie was streng konvensioneel van aard. Vier replikate van elke behandeling is toegepas op elk van die twee wingerdblokke. Die bait-lamina metode is gebruik om die voedingsaktiwiteit van die grond organismes te asses seer. As toevoeging tot die bait-lamina proewe in die wingerd self, is bait-lamina toetse ook in mikro-kosmosse in die laboratorium gedoen met grond afkomstig vanaf die twee wingerdblokke. Om die impak van die verskillende pestisiede op die grondorganismes te ondersoek, is standaard akute toksisteitstoestse en gedragstoetse uitgevoer met die komposerdwurm, Eisenia fetida. Die bait-lamina resultate in die wingerd het getoon dat die voginhoud van die grond die belangrikste rol speel wat die biologiese aktiwiteit van die grondorganismes beïnvloed. Die verskillende behandelings het die biologiese aktiwiteit van die grond fauna geaffekteer, maar seisoenale veranderings is ook uitgesonder as een van die bepalende faktore wat die biologiese prosesse in die grond stuur. Die akute toksisiteitstoetse het getoon dat die aktiewe bestandeie van drie van die pestisiede (mancozeb, penconazole en trifloxystrobin), E. fetida negatief beïnvloed het teen die aanbeveelde konsentrasies wat toegedien is. Die aktiewe bestandeie van die ander twee pestiede (glyphosate en N-asetiel sallisiel suur) het nie die erdwurms nadelig beïnvloed teen die aanbeveelde konsentrasies wat toegedien is nie. Die gedragsproewe het getoon dat E. fetida die LCso-konsentrasies van al die verskillende pestisiede kan waarneem en vermy. Al die erdwurms is positief beïnvloed in die gedragseksperimente met die verskillende pestisiede. Omdat die bait-laminametode sekere beperkings het, was dit moeilik om tot gevolgtrekkings te kom oor wat presies in die grond gebeur. 'n Moontlike verklaring vir die verskillende voedingsaktiwiteite van die grond fauna kan toegereken word aan die migrasie van die grondorganismes na meer leefbare grondhorisonne gedurende die droë somer toestande, wat toevallig met die spuit van die meeste pestisiede ooreenstem. Die ekologiese relevansie van die akute toksisiteitstoetse wat uitgevoer is, moet meer deeglik ondersoek word. Die belangrikheid van die akute toksisteitstoetse is duidelik en het waardevolle informasie gelewer, maar sorg moet geneem word, en die nodige veiligheids faktore moet bepaal word en in ag geneem word, wanneer riskobepalingstudies gedoen word. Die gedragsproewe het getoon dat vir sekere pestisiede E. fetida 'n sensitiewe bioindikator van akute en/of sub-akute letale toksisiteits toetse kan wees, maar nie noodwendig vir ander pestisiede nie. Die doel van laboratoriumstudies is om so veel as moontlik inligting te versamelom vertroubare ekstrapolasie te kan maak na situasies in die veld vanaf laboratorium data. Laboratorium-na-veld ekstrapolasies is dikwels baie gekompliseerd as gevolg van die fisies-chemiese samestelling van die grond, die onvoorspelbare manier waarop chemiese pestisiede met die grond reageer en die reaksie van die grondorganismes op chemiese biosiede in die grond. Verdere studies moet gedoen word om so deeglik maanlik die mate van die impak wat die verskillende bestuurspraktyke op die grond fauna het, te verstaan op Plaisir de Merle.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Both taxonomic diversity and diversity of species interaction networks are experiencing declines as a result of agricultural intensification at habitat and landscape scales. Reversing this trend is a key conservation issue, particularly for important functional groups such as flower-visiting insects and the networks within which they interact. This is of great concern in regions of high conservation priority such as the Cape Floristic Region (CFR), known for its high level of floral and faunal endemism and exceptional species turnover. Holistic approach to conservation in agricultural landscapes involves both preservation of natural land and wildlife friendly management of the farm land to achieve conservation targets. The value of these extensive management approaches is yet to be fully assessed, especially in perennial systems such as vineyards. I examined here the effects of vineyard management and landscape context on species richness and abundance of flower-visiting insects and their species interaction networks. Possible taxon specific effects were verified. I also investigated whether vineyards under organic and conventional management homogenized insect-flower interaction networks and whether vineyards with different management practices vary in patterns of species turnover. I sampled flower-visiting insects and their interactions in organic and conventional vineyards, and in natural reference sites. Inclusion of natural reference sites enabled me to make management recommendations for patches of natural vegetation in CFR agricultural landscape. Statistical models showed taxon-specific benefit of organic farm management, and of landscape (distance to natural habitat). There was benefit to monkey beetles (Scarabaeidae) but not to bees (Apidae). Organic vineyards had a higher number of insect-flower interactions than conventional ones, but vineyards under the two types of management were similar in terms of other important network indices. However, networks of the vineyards were more nested than the natural sites, indicating that they may be potentially more stable to perturbation and random extinctions. Multivariate dispersion tests revealed insect-flower interaction networks were not homogenized by both organic and conventional vineyards across the landscapes. I also found, through additive partitioning, that organic and conventional vineyards were similar in terms of species turnover of bees and flowering plants. The findings of this study provide heuristic value to current debates on the value of vineyard habitats for insect conservation. Both organic and conventional vineyards that promote sustainable management of the non-crop floral vegetation between vineyard rows are potential solutions for conservation of flower-visiting insects and their interactions. Also, attention has to be paid to the quality and connectivity of the natural habitat patches that are within CFR agricultural landscape. Site specific management and assessment of the value of these landscape elements is important. Management approaches such as carefully controlled burning may be beneficial, as the CFR natural vegetation is a fire-driven community. / AFRIKAANSE OPSOMMING: Taksonomiese diversiteit en diversiteit van spesies-interaksie netwerke ondervind beide afnames as gevolg van landboukundige intensifikasie op habitat en landskap skaal. Om die neiging terug te swaai, is ’n sleutel bewaringsaangeleentheid, veral vir belangrike funksionele groepe soos blom-besoekende insekte en die netwerke waarbinne hulle op mekaar inwerk. Dit is van groot kommer in streke met hoë bewaringsprioriteite soos in die Kaapse Floristiese Streek (KFS), bekend vir sy hoë vlak van plant- en dierendemisme en buitengewone spesies kentering. ’n Holistiese benadering tot bewaring van landboukundige landskappe behels beide die bewaring van natuurlike land en natuurlewe-vriendelike bestuur van die plaasgrond om bewaringsdoelwitte te bereik. Die waarde van hierdie ekstensiewe bestuursbenaderings moet nog volledig bepaal word, veral in meerjarige sisteme soos wingerde. Ek het die uitwerkings van wingerdbestuur en landskapsamehang op spesiesrykheid en volopheid van blombesoekende insekte en hulle spesies interaksie netwerke ondersoek. Moontlike takson-spesifieke uitwerkings is nagegaan. Ek het ook ondersoek ingestel of wingerde onder organiese en gebruiklike bestuur ooreenstemmende insek-blom interaksie netwerke met wingerde met verskillende bestuurspraktyke in patroon van spesies kentering gewissel het. Ek het blom-besoekende insekte en hulle interaksies in organiese en konvensionele wingerde, asook in natuurlike verwysingsgebiede gemonster. Insluiting van natuurlike verwysingsgebiede het my in staat gestel om bestuursvoorstelle vir gebiede van natuurlike plantegroei in KFS landboulandskappe voor te stel. Statistiese modelle toon takson-spesifieke voordeel van organiese plaasbestuur en van die landskap (afstand van natuurlike habitat) self. Daar was voordeel vir bobbejaankewers (Scarabaeidae), maar nie vir bye (Apidae) nie. Organiese wingerde het ’n groter getal insek-blom interaksies as konvensionele wingerde gehad, maar wingerde onder beide tipes van bestuur was soortgelyk in terme van ander belangrike netwerk aanduiders. Netwerke van wingerde was egter meer geklomp dan natuurlike gebiede wat aandui dat hulle potensieel meer stabiel betreffende versteuring en lukrake uitsterwings is. Multivariate verspreidingstoetse het aangetoon dat insek-blom interaksie netwerke by beide organiese en konvensionele wingerde oor landskappe nie eenvormig was nie. Ek het ook bevind deur aanvullende verdeling dat organiese en konvensionele wingerde gelykwaardig was in terme van spesies kentering van bye en blomplante. Die bevindings van hierdie studie verskaf heuristise waarde tot huidige debatte oor die waarde van wingerdhabitatte vir insekbewaring. Beide organies en konvensionele wingerde wat volhoubare bestuur van die nie-gewas plantegroei binne wingerdrye bevorder, is moontlike oplossings vir die bewaring van blom-besoekende insekte en hulle wisselwerkings. Bykomend moet aandag gegee word aan die kwaliteit en verbindings van en tussen natuurlike habitat gebiede binne die KFS landboulandskap. Plekspesifieke (plaaslike) bestuur en bepaling van die waarde van hierdie landskapelemente is belangrik. Bestuursbenaderings, soos noukeurig beheerde brand, mag voordelig wees aangesien die KFS natuurlike plantegroei ’n vuurgedrewe gemeenskap is.